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we present high-resolution (0.″16) 870 μm atacama large millimeter/submillimeter array (alma) imaging of 16 luminous ({l}{ir}∼ 4× {10}12 {l}⊙ ) submillimeter galaxies (smgs) from the aless survey of the extended chandra deep field south. this dust imaging traces the dust-obscured star formation in these z∼ 2.5 galaxies on ∼1.3 kpc scales. the emission has a median effective radius of re= 0.″24 ± 0.″02, corresponding to a typical physical size of {r}e= 1.8 ± 0.2 kpc. we derive a median sérsic index of n = 0.9 ± 0.2, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. we use different weighting schemes with the visibilities to search for clumps on 0.″12 (∼1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even moderate signal-to-noise ratio interferometric data. we compare our maps to comparable-resolution hubble space telescope {h}160-band images, finding that the stellar morphologies appear significantly more extended and disturbed, and suggesting that major mergers may be responsible for driving the formation of the compact dust disks we observe. the stark contrast between the obscured and unobscured morphologies may also have implications for sed fitting routines that assume the dust is co-located with the optical/near-ir continuum emission. finally, we discuss the potential of the current bursts of star formation to transform the observed galaxy sizes and light profiles, showing that the z∼ 0 descendants of these smgs are expected to have stellar masses, effective radii, and gas surface densities consistent with the most compact massive ({m}*∼ 1-2 × 1011 {m}⊙ ) early-type galaxies observed locally. | kiloparsec-scale dust disks in high-redshift luminous submillimeter galaxies |
hydrogen lyman-α (lyα) emission has been one of the major observational probes for the high-redshift universe since the first discoveries of high-z lyα-emitting galaxies in the late 1990s. due to the strong lyα emission originated by resonant scattering and recombination of the most abundant element, lyα observations witness not only hii regions of star formation and active galactic nuclei (agns) but also diffuse hi gas in the circumgalactic medium (cgm) and the intergalactic medium (igm). here, we review lyα sources and present theoretical interpretations reached to date. we conclude the following: a typical lyα emitter (lae) at z ≳ 2 with a l* lyα luminosity is a high-z counterpart of a local dwarf galaxy, a compact metal-poor star-forming galaxy (sfg) with an approximate stellar (dark matter halo) mass and star-formation rate of 108-9m⊙ (1010-11m⊙) and 1-10 m⊙ year-1, respectively. high-z sfgs ubiquitously have a diffuse lyα-emitting halo in the cgm extending to the halo virial radius and beyond. remaining neutral hydrogen at the epoch of cosmic reionization makes a strong dimming of lyα emission for galaxies at z > 6 that suggests the late reionization history. the next-generation large-telescope projects will combine lyα emission data with hi lyα absorptions and 21-cm radio data that map out the majority of hydrogen (hi+hii) gas, uncovering the exchanges of (a) matter by outflow and inflow and (b) radiation, relevant to cosmic reionization, between galaxies and the cgm/igm. | observations of the lyman-α universe |
aims: metis is the first solar coronagraph designed for a space mission and is capable of performing simultaneous imaging of the off-limb solar corona in both visible and uv light. the observations obtained with metis aboard the solar orbiter esa-nasa observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona in a square field of view (fov) of ±2.9° in width, with an inner circular fov at 1.6°, thus spanning the solar atmosphere from 1.7 r⊙ to about 9 r⊙, owing to the eccentricity of the spacecraft orbit. due to the uniqueness of the solar orbiter mission profile, metis will be able to observe the solar corona from a close (0.28 au, at the closest perihelion) vantage point, achieving increasing out-of-ecliptic views with the increase of the orbit inclination over time. moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, allow longer-term studies of the off-limb coronal features, thus finally disentangling their intrinsic evolution from effects due to solar rotation.methods: thanks to a novel occultation design and a combination of a uv interference coating of the mirrors and a spectral bandpass filter, metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the uv h i lyman-α line at 121.6 nm. the visible light channel also includes a broadband polarimeter able to observe the linearly polarised component of the k corona. the coronal images in both the uv h i lyman-α and polarised visible light are obtained at high spatial resolution with a spatial scale down to about 2000 km and 15 000 km at perihelion, in the cases of the visible and uv light, respectively. a temporal resolution down to 1 s can be achieved when observing coronal fluctuations in visible light.results: the metis measurements, obtained from different latitudes, will allow for complete characterisation of the main physical parameters and dynamics of the electron and neutral hydrogen/proton plasma components of the corona in the region where the solar wind undergoes the acceleration process and where the onset and initial propagation of coronal mass ejections (cmes) take place. the near-sun multi-wavelength coronal imaging performed with metis, combined with the unique opportunities offered by the solar orbiter mission, can effectively address crucial issues of solar physics such as: the origin and heating/acceleration of the fast and slow solar wind streams; the origin, acceleration, and transport of the solar energetic particles; and the transient ejection of coronal mass and its evolution in the inner heliosphere, thus significantly improving our understanding of the region connecting the sun to the heliosphere and of the processes generating and driving the solar wind and coronal mass ejections.conclusions: this paper presents the scientific objectives and requirements, the overall optical design of the metis instrument, the thermo-mechanical design, and the processing and power unit; reports on the results of the campaigns dedicated to integration, alignment, and tests, and to the characterisation of the instrument performance; describes the operation concept, data handling, and software tools; and, finally, the diagnostic techniques to be applied to the data, as well as a brief description of the expected scientific products. the performance of the instrument measured during calibrations ensures that the scientific objectives of metis can be pursued with success. metis website: http://metis.oato.inaf.it | metis: the solar orbiter visible light and ultraviolet coronal imager |
gas kinematics are an important part of the planet formation process. turbulence influences planetesimal growth and migration from the scale of submicron dust grains through gas-giant planets. radio observations of resolved molecular line emission can directly measure this non-thermal motion and, taking advantage of the layered chemical structure of disks, different molecular lines can be combined to map the turbulence throughout the vertical extent of a protoplanetary disk. here we present alma observations of three molecules (dco+(3-2), c18o(2-1) and co(2-1)) from the disk around hd 163296. we are able to place stringent upper limits (v turb < 0.06cs , <0.05cs , and <0.04csfor co(2-1), c18o(2-1), and dco+(3-2) respectively), corresponding to α ≲ 3 × 10-3, similar to our prior limit derived from co(3-2). this indicates that there is little turbulence throughout the vertical extent of the disk, contrary to theoretical predictions based on the magnetorotational instability and gravitoturbulence. in modeling the dco+ emission, we also find that it is confined to three concentric rings at 65.7 ± 0.9 au, {149.9}-0.7+0.5 {au}, and 259 ± 1 au, indicative of a complex chemical environment. | a three-dimensional view of turbulence: constraints on turbulent motions in the hd 163296 protoplanetary disk using dco+ |
we use asteroseismic data from the kepler satellite to determine fundamental stellar properties of the 66 main-sequence targets observed for at least one full year by the mission. we distributed tens of individual oscillation frequencies extracted from the time series of each star among seven modeling teams who applied different methods to determine radii, masses, and ages for all stars in the sample. comparisons among the different results reveal a good level of agreement in all stellar properties, which is remarkable considering the variety of codes, input physics, and analysis methods employed by the different teams. average uncertainties are of the order of ∼2% in radius, ∼4% in mass, and ∼10% in age, making this the best-characterized sample of main-sequence stars available to date. our predicted initial abundances and mixing-length parameters are checked against inferences from chemical enrichment laws δy/δz and predictions from 3d atmospheric simulations. we test the accuracy of the determined stellar properties by comparing them to the sun, angular diameter measurements, gaia parallaxes, and binary evolution, finding excellent agreement in all cases and further confirming the robustness of asteroseismically determined physical parameters of stars when individual frequencies of oscillation are available. baptised as the kepler dwarfs legacy sample, these stars are the solar-like oscillators with the best asteroseismic properties available for at least another decade. all data used in this analysis and the resulting stellar parameters are made publicly available for the community. | standing on the shoulders of dwarfs: the kepler asteroseismic legacy sample. ii.radii, masses, and ages |
we explore star formation histories (sfhs) of galaxies based on the evolution of the star formation rate stellar mass relation (sfr-m*). using data from the fourstar galaxy evolution survey (zfourge) in combination with far-ir imaging from the spitzer and herschel observatories we measure the sfr-m* relation at 0.5 < z < 4. similar to recent works we find that the average infrared spectral energy distributions of galaxies are roughly consistent with a single infrared template across a broad range of redshifts and stellar masses, with evidence for only weak deviations. we find that the sfr-m* relation is not consistent with a single power law of the form {sfr}\propto {m}*αat any redshift; it has a power law slope of α ∼ 1 at low masses, and becomes shallower above a turnover mass (m0) that ranges from 109.5 to 1010.8 m⊙, with evidence that m0 increases with redshift. we compare our measurements to results from state-of-the-art cosmological simulations, and find general agreement in the slope of the sfr-m* relation albeit with systematic offsets. we use the evolving sfr-m* sequence to generate sfhs, finding that typical sfrs of individual galaxies rise at early times and decline after reaching a peak. this peak occurs earlier for more massive galaxies. we integrate these sfhs to generate mass growth histories and compare to the implied mass growth from the evolution of the stellar mass function (smf). we find that these two estimates are in broad qualitative agreement, but that there is room for improvement at a more detailed level. at early times the sfhs suggest mass growth rates that are as much as 10× higher than inferred from the smf. however, at later times the sfhs under-predict the inferred evolution, as is expected in the case of additional growth due to mergers. this paper includes data gathered with the 6.5 m magellan telescopes located at las campanas observatory, chile. | the sfr-m* relation and empirical star-formation histories from zfourge* at 0.5 < z < 4 |
supermassive black holes are found at the centres of massive galaxies. during the growth of these black holes they light up to become visible as active galactic nuclei (agns) and release extraordinary amounts of energy across the electromagnetic spectrum. this energy is widely believed to regulate the rate of star formation in the black holes' host galaxies via so-called agn feedback. however, the details of how and when this occurs remain uncertain from both an observational and theoretical perspective. i review some of the theoretical motivation and observational results and discuss possible observational signatures of the impact of supermassive black hole growth on star formation. | impact of supermassive black hole growth on star formation |
the kinematics of the milky way disc as a function of age are well measured at the solar radius, but have not been studied over a wider range of galactocentric radii. here, we measure the kinematics of mono-age, mono-[fe/h] populations in the low and high [α/fe] discs between 4 ≲ r ≲ 13 kpc and |z| ≲ 2 kpc using 65 719 stars in common between apogee dr14 and gaia dr2 for which we estimate ages using a bayesian neural network model trained on asteroseismic ages. we determine the vertical and radial velocity dispersions, finding that the low and high [α/fe] discs display markedly different age-velocity dispersion relations (avrs) and shapes σz/σr. the high [α/fe] disc has roughly flat avrs and constant σz/σr = 0.64 ± 0.04, whereas the low [α/fe] disc has large variations in this ratio that positively correlate with the mean orbital radius of the population at fixed age. the high [α/fe] disc component's flat avrs and constant σz/σr clearly indicate an entirely different heating history. outer disc populations also have flatter radial avrs than those in the inner disc, likely due to the waning effect of spiral arms. our detailed measurements of avrs and σz/σr across the disc indicate that low [α/fe], inner disc (r ≲ 10 kpc) stellar populations are likely dynamically heated by both giant molecular clouds and spiral arms, while the observed trends for outer disc populations require a significant contribution from another heating mechanism such as satellite perturbations. we also find that outer disc populations have slightly positive mean vertical and radial velocities likely because they are part of the warped disc. | dynamical heating across the milky way disc using apogee and gaia |
in federated learning, a central server coordinates the training of a single model on a massively distributed network of devices. this setting can be naturally extended to a multi-task learning framework, to handle real-world federated datasets that typically show strong statistical heterogeneity among devices. despite federated multi-task learning being shown to be an effective paradigm for real-world datasets, it has been applied only on convex models. in this work, we introduce virtual, an algorithm for federated multi-task learning for general non-convex models. in virtual the federated network of the server and the clients is treated as a star-shaped bayesian network, and learning is performed on the network using approximated variational inference. we show that this method is effective on real-world federated datasets, outperforming the current state-of-the-art for federated learning, and concurrently allowing sparser gradient updates. | variational federated multi-task learning |
most of the hydrogen in the intergalactic medium (igm) was rapidly ionized at high redshifts. while observations have established that reionization occurred, observational constraints on the high-redshift ionizing emissivity remain elusive. here, we present a new analysis of the low-redshift lyman continuum survey (lzlcs) and literature observations, a combined sample of 89 star-forming galaxies at redshifts near 0.3 with hubble space telescope observations of their ionizing continua (or lyman continuum, lyc). we find a strong (6σ significant) inverse correlation between the continuum slope at 1550 å (defined as f$_\lambda \propto \lambda ^{\beta ^{1550}_{\rm obs}}$) and both the lyc escape fraction (fesc, lyc) and fesc, lyc times the ionizing photon production efficiency (ξion). on average, galaxies with redder continuum slopes have smaller fesc, lyc than galaxies with bluer slopes mainly due to higher dust attenuation. more than 5 per cent (20 per cent) of the lyc emission escapes galaxies with $\beta _{\rm obs}^{1550}$ <-2.1 (-2.6). we find strong correlations between $\beta _{\rm obs}^{1550}$ and the [o iii]/[o ii] flux ratio (at 7.5σ significance), galaxy stellar mass (at 5.9σ), the gas-phase metallicity (at 4.6σ), and the observed far-ultraviolet absolute magnitude (at 3.4σ). using previous observations of $\beta _{\rm obs}^{1550}$ at high redshift, we estimate the evolution of fesc, lyc with both redshift and galaxy magnitude. the lzlcs observations suggest that fainter and lower mass galaxies dominate the ionizing photon budget at higher redshift, possibly due to their rapidly evolving metal and dust content. finally, we use our correlation between $\beta _{\rm obs}^{1550}$ and fesc, lyc × ξion to predict the ionizing emissivity of galaxies during the epoch of reionization. our estimated emissivities match igm observations, and suggest that star-forming galaxies emit sufficient lyc photons into the igm to exceed recombinations near redshifts of 7-8. | the far-ultraviolet continuum slope as a lyman continuum escape estimator at high redshift |
we analyse the first giant molecular cloud (gmc) simulation to follow the formation of individual stars and their feedback from jets, radiation, winds, and supernovae, using the starforge framework in the gizmo code. we evolve the gmc for $\sim 9 \rm myr$, from initial turbulent collapse to dispersal by feedback. protostellar jets dominate feedback momentum initially, but radiation and winds cause cloud disruption at $\sim 8{{\ \rm per\ cent}}$ star formation efficiency (sfe), and the first supernova at $8.3\, \rm myr$ comes too late to influence star formation significantly. the per-free-fall sfe is dynamic, accelerating from 0 per cent to $\sim 18{{\ \rm per\ cent}}$ before dropping quickly to <1 per cent, but the estimate from yso counts compresses it to a narrower range. the primary cluster forms hierarchically and condenses to a brief ($\sim 1\, \mathrm{myr}$) compact ($\sim 1\, \rm pc$) phase, but does not virialize before the cloud disperses, and the stars end as an unbound expanding association. the initial mass function resembles the chabrier (2005) form with a high-mass slope α = -2 and a maximum mass of 55 m⊙. stellar accretion takes $\sim 400\, \rm kyr$ on average, but $\gtrsim 1\,\rm myr$ for >10 m⊙ stars, so massive stars finish growing latest. the fraction of stars in multiples increase as a function of primary mass, as observed. overall, the simulation much more closely resembles reality, compared to previous versions that neglected different feedback physics entirely. but more detailed comparison with synthetic observations will be needed to constrain the theoretical uncertainties. | the dynamics and outcome of star formation with jets, radiation, winds, and supernovae in concert |
we present a targeted search for continuous gravitational waves (gws) from 236 pulsars using data from the third observing run of ligo and virgo (o3) combined with data from the second observing run (o2). searches were for emission from the l = m = 2 mass quadrupole mode with a frequency at only twice the pulsar rotation frequency (single harmonic) and the l = 2, m = 1, 2 modes with a frequency of both once and twice the rotation frequency (dual harmonic). no evidence of gws was found, so we present 95% credible upper limits on the strain amplitudes h 0 for the single-harmonic search along with limits on the pulsars' mass quadrupole moments q 22 and ellipticities ɛ. of the pulsars studied, 23 have strain amplitudes that are lower than the limits calculated from their electromagnetically measured spin-down rates. these pulsars include the millisecond pulsars j0437-4715 and j0711-6830, which have spin-down ratios of 0.87 and 0.57, respectively. for nine pulsars, their spin-down limits have been surpassed for the first time. for the crab and vela pulsars, our limits are factors of ~100 and ~20 more constraining than their spin-down limits, respectively. for the dual-harmonic searches, new limits are placed on the strain amplitudes c 21 and c 22. for 23 pulsars, we also present limits on the emission amplitude assuming dipole radiation as predicted by brans-dicke theory. | searches for gravitational waves from known pulsars at two harmonics in the second and third ligo-virgo observing runs |
recent jwst/nircam imaging taken for the ultra-deep uncover program reveals a very red dropout object at z phot ≃ 7.6, triply imaged by the galaxy cluster a2744 (z d = 0.308). all three images are very compact, i.e., unresolved, with a delensed size upper limit of re≲ 35 pc. the images have apparent magnitudes of m f444w ~ 25-26 ab, and the magnification-corrected absolute uv magnitude of the source is m uv,1450 = -16.81 ± 0.09. from the sum of observed fluxes and from a spectral energy distribution (sed) analysis, we obtain estimates of the bolometric luminosities of the source of l bol ≳ 1043 erg s-1 and l bol ~ 1044-1046 erg s-1, respectively. based on its compact, point-like appearance, its position in color-color space, and the sed analysis, we tentatively conclude that this object is a uv-faint dust-obscured quasar-like object, i.e., an active galactic nucleus at high redshift. we also discuss other alternative origins for the object's emission features, including a massive star cluster, population iii, supermassive, or dark stars, or a direct-collapse black hole. although populations of red galaxies at similar photometric redshifts have been detected with jwst, this object is unique in that its high-redshift nature is corroborated geometrically by lensing, that it is unresolved despite being magnified-and thus intrinsically even more compact-and that it occupies notably distinct regions in both size-luminosity and color-color space. planned uncover jwst/nirspec observations, scheduled in cycle 1, will enable a more detailed analysis of this object. | jwst uncover: extremely red and compact object at z phot ≃ 7.6 triply imaged by a2744 |
the high-redshift intergalactic medium (igm) and the primeval galaxy population are rapidly becoming the new frontier of extragalactic astronomy. we investigate the igm properties and their connection to galaxies at z ≥ 5.5 under different assumptions for the ionizing photon escape and the nature of dark matter, employing our novel thesan radiation-hydrodynamical simulation suite, designed to provide a comprehensive picture of the emergence of galaxies in a full reionization context. our simulations have realistic 'late' reionization histories, match available constraints on global igm properties, and reproduce the recently observed rapid evolution of the mean free path of ionizing photons. we additionally examine high-z lyman-α transmission. the optical depth evolution is consistent with data, and its distribution suggests an even-later reionization than simulated, although with a strong sensitivity to the source model. we show that the effects of these two unknowns can be disentangled by characterizing the spectral shape and separation of lyman-α transmission regions, opening up the possibility to observationally constrain both. for the first time in simulations, thesan reproduces the modulation of the lyman-α flux as a function of galaxy distance, demonstrating the power of coupling a realistic galaxy formation model with proper radiation hydrodynamics. we find this feature to be extremely sensitive on the timing of reionization, while being relatively insensitive to the source model. overall, thesan produces a realistic igm and galaxy population, providing a robust framework for future analysis of the high-z universe. | the thesan project: properties of the intergalactic medium and its connection to reionization-era galaxies |
in recent years, 2d layered materials have received considerable research interest on account of their substantial material systems and unique physicochemical properties. among them, 2d layered transition metal dichalcogenides (tmds), a star family member, have already been explored over the last few years and have exhibited excellent performance in electronics, catalysis, and other related fields. however, to fulfill the requirement for practical application, the batch production of 2d tmds is essential. recently, the chemical vapor deposition (cvd) technique was considered as an elegant alternative for successfully growing 2d tmds and their heterostructures. the latest research advances in the controllable synthesis of 2d tmds and related heterostructures/superlattices via the cvd approach are illustrated here. the controlled growth behavior, preparation strategies, and breakthroughs on the synthesis of new 2d tmds and their heterostructures, as well as their unique physical phenomena, are also discussed. recent progress on the application of cvd‑grown 2d materials is revealed with particular attention to electronics/optoelectronic devices and catalysts. finally, the challenges and future prospects are considered regarding the current development of 2d tmds and related heterostructures. | recent progress in cvd growth of 2d transition metal dichalcogenides and related heterostructures |
the coronal activity-rotation relationship is considered to be a proxy for the underlying stellar dynamo responsible for magnetic activity in solar and late-type stars. while this has been studied in considerable detail for partly convective stars that are believed to operate an interface dynamo, it is poorly unconstrained in fully convective stars that lack the necessary shear layer between radiative core and the convective envelope. we present new x-ray observations of 19 slowly rotating fully convective stars with rotation periods from the mearth project. we use these to calculate x-ray luminosities (or upper limits for undetected sources) and combine these with existing measurements. we confirm the existence of fully convective stars in the x-ray unsaturated regime and find that these objects follow the same rotation-activity relationship seen for partly convective stars. we measure the power-law slope of the relationship between rossby number (the ratio of the rotation period to the convective turnover time) and the fractional x-ray luminosity for x-ray unsaturated fully convective stars for the first time, and find it to be consistent with that found for partly convective stars. we discuss this implications of this result for our understanding of stellar magnetic dynamos in fully- and partly convective stars. finally, we also use this data to improve empirical estimates of the convective turnover time for fully convective stars. | the stellar rotation-activity relationship in fully convective m dwarfs |
electron and ion energization (i.e., heating and nonthermal acceleration) is a fundamental, but poorly understood, outcome of plasma turbulence. in this work, we present new results on this topic from particle-in-cell simulations of driven turbulence in collisionless, relativistic electron-ion plasma. we focus on temperatures such that ions (protons) are subrelativistic and electrons are ultrarelativistic, a regime relevant for high-energy astrophysical systems such as hot accretion flows onto black holes. we find that ions tend to be preferentially heated, gaining up to an order of magnitude more energy than electrons, and propose a simple empirical formula to describe the electron-ion energy partition as a function of the ratio of electron-to-ion gyroradii (which in turn is a function of initial temperatures and plasma beta). we also find that while efficient nonthermal particle acceleration occurs for both species in the ultrarelativistic regime, nonthermal electron populations are diminished with decreasing temperature whereas nonthermal ion populations are essentially unchanged. these results have implications for modeling and interpreting observations of hot accretion flows. | electron and ion energization in relativistic plasma turbulence |
nuclear star clusters surrounding supermassive black holes (smbhs) in galactic nuclei contain large numbers of stars, black holes (bhs), and neutron stars (nss), a fraction of which are likely to form binaries. these binaries were suggested to form a triple system with the smbh, which acts as a perturber and may enhance bh and ns mergers via the lidov-kozai mechanism. we follow-up previous studies, but for the first time perform an extensive statistical study of bh-bh, ns-ns, and bh-ns binary mergers by means of direct high-precision regularized n-body simulations, including post-newtonian (pn) terms up to order pn2.5. we consider different smbh masses, slopes for the bh mass function, binary semimajor axis and eccentricity distributions, and different spatial distributions for the binaries. we find that the merger rates are a decreasing function of the smbh mass and are in the ranges ∼0.17-0.52, ∼0.06-0.10, and ∼0.04-0.16 gpc-3 yr-1 for bh-bh, bh-ns, and ns-ns binaries, respectively. however, the rate estimate from this channel remains highly uncertain and depends on the specific assumptions regarding the star formation history in galactic nuclei and the supply rate of compact objects (cos). we find that {∼ } 10-20{{ per cent}} of the mergers enter the ligo band with eccentricities ≳0.1. we also compare our results to the secular approximation, and show that n-body simulations generally predict a larger number of mergers. finally, these events can also be observable via their electromagnetic counterparts, thus making these co mergers especially valuable for cosmological and astrophysical purposes. | black hole and neutron star mergers in galactic nuclei |
we use the observed properties of fast radio bursts (frbs) and a number of general physical considerations to provide a broad-brush model for the physical properties of frb sources and the radiation mechanism. we show that the magnetic field in the source region should be at least 1014 g. this strong field is required to ensure that the electrons have sufficiently high ground state landau energy so that particle collisions, instabilities and strong electromagnetic fields associated with the frb radiation do not perturb electrons' motion in the direction transverse to the magnetic field and destroy their coherent motion; coherence is required by the high observed brightness temperature of frb radiation. the electric field in the source region required to sustain particle motion for a wave period is estimated to be of the order of 1011 esu. these requirements suggest that frbs are produced near the surface of magnetars perhaps via forced reconnection of magnetic fields to produce episodic, repeated, outbursts. the beaming-corrected energy release in these bursts is estimated to be about 1036 erg, whereas the total energy in the magnetic field is at least ∼1045 erg. we provide a number of predictions for this model which can be tested by future observations. one of which is that short duration frb-like bursts should exist at much higher frequencies, possibly up to optical. | fast radio burst source properties and curvature radiation model |
we present a suite of 15 cosmological zoom-in simulations of isolated dark matter haloes, all with masses of mhalo ≈ 1010 m⊙ at z = 0, in order to understand the relationship among halo assembly, galaxy formation and feedback's effects on the central density structure in dwarf galaxies. these simulations are part of the feedback in realistic environments (fire) project and are performed at extremely high resolution (mbaryon = 500 m⊙, mdm = 2500 m⊙). the resultant galaxies have stellar masses that are consistent with rough abundance matching estimates, coinciding with the faintest galaxies that can be seen beyond the virial radius of the milky way (m*/m⊙ ≈ 105 - 107). this non-negligible spread in stellar mass at z = 0 in haloes within a narrow range of virial masses is strongly correlated with central halo density or maximum circular velocity vmax, both of which are tightly linked to halo formation time. much of this dependence of m* on a second parameter (beyond mhalo) is a direct consequence of the mhalo ∼ 1010 m⊙ mass scale coinciding with the threshold for strong reionization suppression: the densest, earliest-forming haloes remain above the uv-suppression scale throughout their histories while late-forming systems fall below the uv-suppression scale over longer periods and form fewer stars as a result. in fact, the latest-forming, lowest-concentration halo in our suite fails to form any stars. haloes that form galaxies with m⋆ ≳ 2 × 106 m⊙ have reduced central densities relative to dark-matter-only simulations, and the radial extent of the density modifications is well-approximated by the galaxy half-mass radius r1/2. lower-mass galaxies do not modify their host dark matter haloes at the mass scale studied here. this apparent stellar mass threshold of m⋆ ≈ 2 × 106 - 2 × 10- 4 mhalo is broadly consistent with previous work and provides a testable prediction of fire feedback models in λcold dark matter. | fire in the field: simulating the threshold of galaxy formation |
gravitational-wave astronomy has been firmly established with the detection of gravitational waves from the merger of ten stellar-mass binary black holes and a neutron star binary. this paper reports on the all-sky search for gravitational waves from intermediate mass black hole binaries in the first and second observing runs of the advanced ligo and virgo network. the search uses three independent algorithms: two based on matched filtering of the data with waveform templates of gravitational-wave signals from compact binaries, and a third, model-independent algorithm that employs no signal model for the incoming signal. no intermediate mass black hole binary event is detected in this search. consequently, we place upper limits on the merger rate density for a family of intermediate mass black hole binaries. in particular, we choose sources with total masses m =m1+m2∈[120 ,800 ] m⊙ and mass ratios q =m2/m1∈[0.1 ,1.0 ]. for the first time, this calculation is done using numerical relativity waveforms (which include higher modes) as models of the real emitted signal. we place a most stringent upper limit of 0.20 gpc-3 yr-1 (in comoving units at the 90% confidence level) for equal-mass binaries with individual masses m1 ,2=100 m⊙ and dimensionless spins χ1 ,2=0.8 aligned with the orbital angular momentum of the binary. this improves by a factor of ∼5 that reported after advanced ligo's first observing run. | search for intermediate mass black hole binaries in the first and second observing runs of the advanced ligo and virgo network |
we study the gas phase metallicity (o/h) and nitrogen abundance gradients traced by star-forming regions in a representative sample of 550 nearby galaxies in the stellar mass range 109-1011.5 m⊙ with resolved spectroscopic data from the sloan digital sky survey iv mapping nearby galaxies at apache point observatory survey. using strong-line ratio diagnostics (r23 and o3n2 for metallicity and n2o2 for n/o) and referencing to the effective (half-light) radius (re), we find that the metallicity gradient steepens with stellar mass, lying roughly flat among galaxies with log (m⋆/m⊙) = 9.0 but exhibiting slopes as steep as -0.14 dex r_e^{-1} at log (m⋆/m⊙) = 10.5 (using r23, but equivalent results are obtained using o3n2). at higher masses, these slopes remain typical in the outer regions of our sample (r > 1.5re), but a flattening is observed in the central regions (r < 1re). in the outer regions (r > 2.0re), we detect a mild flattening of the metallicity gradient in stacked profiles, although with low significance. the n/o ratio gradient provides complementary constraints on the average chemical enrichment history. unlike the oxygen abundance, the average n/o profiles do not flatten out in the central regions of massive galaxies. the metallicity and n/o profiles both depart significantly from an exponential form, suggesting a disconnect between chemical enrichment and stellar mass surface density on local scales. in the context of inside-out growth of discs, our findings suggest that central regions of massive galaxies today have evolved to an equilibrium metallicity, while the nitrogen abundance continues to increase as a consequence of delayed secondary nucleosynthetic production. | sdss iv manga - metallicity and nitrogen abundance gradients in local galaxies |
we trace the evolution of research on extreme solar and solar-terrestrial events from the 1859 carrington event to the rapid development of the last twenty years. our focus is on the largest observed/inferred/theoretical cases of sunspot groups, flares on the sun and sun-like stars, coronal mass ejections, solar proton events, and geomagnetic storms. the reviewed studies are based on modern observations, historical or long-term data including the auroral and cosmogenic radionuclide record, and kepler observations of sun-like stars. we compile a table of 100- and 1000-year events based on occurrence frequency distributions for the space weather phenomena listed above. questions considered include the sun-like nature of superflare stars and the existence of impactful but unpredictable solar "black swans" and extreme "dragon king" solar phenomena that can involve different physics from that operating in events which are merely large. | extreme solar events |
the pencil code is a highly modular physics-oriented simulation code that can be adapted to a wide range of applications. it is primarily designed to solve partial differential equations (pdes) of compressible hydrodynamics and has lots of add-ons ranging from astrophysical magnetohydrodynamics (mhd) to meteorological cloud microphysics and engineering applications in combustion. nevertheless, the framework is general and can also be applied to situations not related to hydrodynamics or even pdes, for example when just the message passing interface or input/output strategies of the code are to be used. the code can also evolve lagrangian (inertial and noninertial) particles, their coagulation and condensation, as well as their interaction with the fluid. | the pencil code, a modular mpi code for partial differential equations and particles: multipurpose and multiuser-maintained |
the james webb space telescope (jwst) discovered several luminous high-redshift galaxy candidates with stellar masses of m * ≳ 109 m ⊙ at photometric redshifts z phot ≳ 10, which allows to constrain galaxy and structure formation models. for example, adams et al. identified the candidate id 1514 with ${\mathrm{log}}_{10}({m}_{* }/{m}_{\odot })={9.8}_{-0.2}^{+0.2}$ located at ${z}_{\mathrm{phot}}={9.85}_{-0.12}^{+0.18}$ and naidu et al. found even more distant candidates labeled as gl-z11 and gl-z13 with ${\mathrm{log}}_{10}({m}_{* }/{m}_{\odot })={9.4}_{-0.3}^{+0.3}$ at ${z}_{\mathrm{phot}}={10.9}_{-0.4}^{+0.5}$ and ${\mathrm{log}}_{10}({m}_{* }/{m}_{\odot })={9.0}_{-0.4}^{+0.3}$ at ${z}_{\mathrm{phot}}={13.1}_{-0.7}^{+0.8}$ , respectively. assessing the computations of the illustristng (tng50-1 and tng100-1) and eagle projects, we investigate if the stellar mass buildup as predicted by the λcdm paradigm is consistent with these observations assuming that the early jwst calibration is correct and that the candidates are indeed located at z ≳ 10. galaxies formed in the λcdm paradigm are by more than an order of magnitude less massive in stars than the observed galaxy candidates implying that the stellar mass buildup is more efficient in the early universe than predicted by the λcdm models. this in turn would suggest that structure formation is more enhanced at z ≳ 10 than predicted by the λcdm framework. we show that different star formation histories could reduce the stellar masses of the galaxy candidates alleviating the tension. finally, we calculate the galaxy-wide initial mass function (gwimf) of the galaxy candidates assuming the integrated galaxy imf theory. the gwimf becomes top-heavy for metal-poor star-forming galaxies decreasing therewith the stellar masses compared to an invariant canonical imf. | has jwst already falsified dark-matter-driven galaxy formation? |
we present and study a large suite of high-resolution cosmological zoom-in simulations, using the fire-2 treatment of mechanical and radiative feedback from massive stars, together with explicit treatment of magnetic fields, anisotropic conduction and viscosity (accounting for saturation and limitation by plasma instabilities at high β), and cosmic rays (crs) injected in supernovae shocks (including anisotropic diffusion, streaming, adiabatic, hadronic and coulomb losses). we survey systems from ultrafaint dwarf (m_{\ast }∼ 104 m_{⊙}, m_halo∼ 109 m_{⊙}) through milky way/local group (mw/lg) masses, systematically vary uncertain cr parameters (e.g. the diffusion coefficient κ and streaming velocity), and study a broad ensemble of galaxy properties [masses, star formation (sf) histories, mass profiles, phase structure, morphologies, etc.]. we confirm previous conclusions that magnetic fields, conduction, and viscosity on resolved (≳ 1 pc) scales have only small effects on bulk galaxy properties. crs have relatively weak effects on all galaxy properties studied in dwarfs (m_{\ast } ≪ 10^{10} m_{⊙}, m_halo ≲ 10^{11} m_{⊙}), or at high redshifts (z ≳ 1-2), for any physically reasonable parameters. however, at higher masses (m_halo ≳ 10^{11} m_{⊙}) and z ≲ 1-2, crs can suppress sf and stellar masses by factors ∼2-4, given reasonable injection efficiencies and relatively high effective diffusion coefficients κ ≳ 3× 10^{29} cm^{2 s^{-1}}. at lower κ, crs take too long to escape dense star-forming gas and lose their energy to collisional hadronic losses, producing negligible effects on galaxies and violating empirical constraints from spallation and γ-ray emission. at much higher κ crs escape too efficiently to have appreciable effects even in the cgm. but around κ ∼ 3× 10^{29} cm^{2 s^{-1}}, crs escape the galaxy and build up a cr-pressure-dominated halo which maintains approximate virial equilibrium and supports relatively dense, cool (t ≪ 106 k) gas that would otherwise rain on to the galaxy. cr `heating' (from collisional and streaming losses) is never dominant. | but what about...: cosmic rays, magnetic fields, conduction, and viscosity in galaxy formation |
gravitational wave (gw) measurements will provide insight into the population of coalescing compact binaries throughout the universe. we describe and demonstrate a flexible parametric method to infer the event rate as a function of compact binary parameters, accounting for poisson error and selection biases. using synthetic data based on projections for ligo and virgo's third observing run (o3), we discuss how well gw measurements could constrain the mass and spin distribution of coalescing neutron stars and black holes (bhs) in the near future, within the context of several phenomenological models described in this work. we demonstrate that only a few tens of events can enable astrophysically significant constraints on the spin magnitude and orientation distribution of bhs in merging binaries. we discuss how astrophysical priors or other measurements can inform the interpretation of future measurements. using publicly available results, we estimate the event rate versus mass for binary black holes (bbhs). to connect to previously published work, we provide estimates including reported o2 bbh candidates, making several unwarranted but simplifying assumptions for the sensitivity of the network and completeness of the reported set of events. consistent with prior work, we find bhs in binaries likely have low natal spin. with available results and a population favoring low spin, we cannot presently constrain the typical misalignments of the binary black hole population. all of the tools described in this work are publicly available and ready-to-use to interpret real or synthetic ligo data, and to synthesize projected data from future observing runs. | reconstructing phenomenological distributions of compact binaries via gravitational wave observations |
a general theory of the onset and development of the plasmoid instability is formulated by means of a principle of least time. the scaling relations for the final aspect ratio, transition time to rapid onset, growth rate, and number of plasmoids are derived and shown to depend on the initial perturbation amplitude (ŵ 0 ) , the characteristic rate of current sheet evolution (1/τ), and the lundquist number (s). they are not simple power laws, and are proportional to sατβ[lnf (s ,τ,ŵ 0) ] σ . the detailed dynamics of the instability is also elucidated, and shown to comprise of a period of quiescence followed by sudden growth over a short time scale. | general theory of the plasmoid instability |
we present specific star formation rates (ssfrs) for 40 ultraviolet (uv)-bright galaxies at z ~ 7-8 observed as part of the reionization era bright emission line survey (rebels) atacama large millimeter/submillimeter array (alma) large programme. the ssfrs are derived using improved star formation rate (sfr) calibrations and spectral energy distribution (sed)-based stellar masses, made possible by measurements of far-infrared (fir) continuum emission and [c ii]-based spectroscopic redshifts. the median ssfr of the sample is $18_{-5}^{+7}$ gyr-1, significantly larger than literature measurements lacking constraints in the fir, reflecting the larger obscured sfrs derived from the dust continuum relative to that implied by the uv+optical sed. we suggest that such differences may reflect spatial variations in dust across these luminous galaxies, with the component dominating the fir distinct from that dominating the uv. we demonstrate that the inferred stellar masses (and hence ssfrs) are strongly dependent on the assumed star formation history in reionization-era galaxies. when large ssfr galaxies (a population that is common at z > 6) are modelled with non-parametric star formation histories, the derived stellar masses can increase by an order of magnitude relative to constant star formation models, owing to the presence of a significant old stellar population that is outshined by the recent burst. the [c ii] line widths in the largest ssfr systems are often very broad, suggesting dynamical masses capable of accommodating an old stellar population suggested by non-parametric models. regardless of these systematic uncertainties among derived parameters, we find that ssfrs increase rapidly toward higher redshifts for massive galaxies (9.6 < log (m*/m⊙) < 9.8), evolving as (1 + z)1.7 ± 0.3, broadly consistent with expectations from the evolving baryon accretion rates. | the alma rebels survey: specific star formation rates in the reionization era |
one proposed formation channel for stellar mass black holes (bhs) is through hierarchical mergers of smaller bhs. repeated mergers between comparable mass bhs leave an imprint on the spin of the resulting bh since the final bh spin is largely determined by the orbital angular momentum of the binary. we find that for stellar mass bhs forming hierarchically the distribution of spin magnitudes is universal, with a peak at a∼ 0.7 and little support below a∼ 0.5. we show that the spin distribution is robust against changes to the mass ratio of the merging binaries, the initial spin distribution of the first generation of bhs, and the number of merger generations. while we assume an isotropic distribution of initial spin directions, spins that are preferentially aligned or antialigned do not qualitatively change our results. we also consider a “cluster catastrophe” model for bh formation in which we allow for mergers of arbitrary mass ratios and show that this scenario predicts a unique spin distribution that is similar to the universal distribution derived for major majors. we explore the ability of spin measurements from ground-based gravitational-wave (gw) detectors to constrain hierarchical merger scenarios. we apply a hierarchical bayesian mixture model to mock gw data and argue that the fraction of bhs that formed through hierarchical mergers will be constrained with { o }(100) ligo binary black hole detections, while with { o }(10) detections we could falsify a model in which all component bhs form hierarchically. | are ligo's black holes made from smaller black holes? |
we present detections of [o iii] λ4363 and direct-method metallicities for star-forming galaxies at z = 1.7-3.6. we combine new measurements from the mosfire deep evolution field (mosdef) survey with literature sources to construct a sample of 18 galaxies with direct-method metallicities at z > 1, spanning 7.5 < 12+log(o/h) < 8.2 and log(m*/m⊙) = 7-10. we find that strong-line calibrations based on local analogues of high-redshift galaxies reliably reproduce the metallicity of the z > 1 sample on average. we construct the first mass-metallicity relation at z > 1 based purely on direct-method o/h, finding a slope that is consistent with strong-line results. direct-method o/h evolves by ≲0.1 dex at fixed m* and star formation rate from z ∼ 0 to 2.2. we employ photoionization models to constrain the ionization parameter and ionizing spectrum in the high-redshift sample. stellar models with supersolar o/fe and binary evolution of massive stars are required to reproduce the observed strong-line ratios. we find that the z > 1 sample falls on the z ∼ 0 relation between ionization parameter and o/h, suggesting no evolution of this relation from z ∼ 0 to z ∼ 2. these results suggest that the offset of the strong-line ratios of this sample from local excitation sequences is driven primarily by a harder ionizing spectrum at fixed nebular metallicity compared to what is typical at z ∼ 0, naturally explained by supersolar o/fe at high redshift caused by rapid formation time-scales. given the extreme nature of our z > 1 sample, the implications for representative z ∼ 2 galaxy samples at ∼1010 m⊙ are unclear, but similarities to z > 6 galaxies suggest that these conclusions can be extended to galaxies in the epoch of reionization. | the mosdef survey: direct-method metallicities and ism conditions at z ∼ 1.5-3.5 |
we explore the connection between the uv luminosity functions (lfs) of high-z galaxies and the distribution of stellar masses and star formation histories (sfhs) in their host dark matter halos. we provide a baseline for a redshift-independent star formation efficiency model to which observations and models can be compared. our model assigns a star formation rate (sfr) to each dark matter halo based on the growth rate of the halo and a redshift-independent star formation efficiency. the dark matter halo accretion rate is obtained from a high-resolution n-body simulation in order to capture the stochasticity in accretion histories and to obtain spatial information for the distribution of galaxies. the halo mass dependence of the star formation efficiency is calibrated at z = 4 by requiring a match to the observed uv lf at this redshift. the model then correctly predicts the observed uv lf at z = 5-10. we present predictions for the uv luminosity and stellar mass functions, jwst number counts, and sfhs. in particular, we find a stellar-to-halo mass relation at z = 4-10 that scales with halo mass at m h < 1011 m ⊙ as m ⋆ ∝ m h 2, with a normalization that is higher than the relation inferred at z = 0. the average sfrs increase as a function of time to z = 4, although there is significant scatter around the average: about 6% of the z = 4 galaxies show no significant mass growth. using these sfhs, we present redshift-dependent uv-to-sfr conversion factors, mass return fractions, and mass-to-light ratios for different initial mass functions and metallicities, finding that current estimates of the cosmic sfr density at z ∼ 10 may be overestimated by ∼0.1-0.2 dex. | a redshift-independent efficiency model: star formation and stellar masses in dark matter halos at z ≳ 4 |
polarization measurements of thermal radiation from magnetic white dwarf (mwd) stars have been proposed as a probe of axion-photon mixing. the radiation leaving the surface of the mwd is unpolarized, but if low-mass axions exist then photons polarized parallel to the direction of the mwd's magnetic field may convert into axions, which induces a linear polarization dependent on the strength of the axion-photon coupling ga γ γ . we model this process by using the formalism of axion-photon mixing in the presence of strong-field vacuum birefringence to show that of all stellar types mwds are the most promising targets for axion-induced polarization searches. we then consider linear polarization data from multiple mwds, including sdss j135141 and grw +70 °8247 , to show that after rigorously accounting for astrophysical uncertainties the axion-photon coupling is constrained to |ga γ γ|≲5.4 ×10-12 gev-1 at 95% confidence for axion masses ma≲3 ×10-7 ev . this upper limit puts in tension the previously-suggested explanation of the anomalous transparency of the universe to tev gamma-rays in terms of axions. we identify mwd targets for which future data and modeling efforts could further improve the sensitivity to axions. | upper limit on the axion-photon coupling from magnetic white dwarf polarization |
the kepler mission has provided exquisite data to perform an ensemble asteroseismic analysis on evolved stars. in this work we systematically characterize solar-like oscillations and granulation for 16,094 oscillating red giants, using end-of-mission long-cadence data. we produced a homogeneous catalog of the frequency of maximum power (typical uncertainty {σ }{ν \max }=1.6 % ), the mean large frequency separation ({σ }{{δ }ν }=0.6 % ), oscillation amplitude ({σ }{{a}}=4.7 % ), granulation power ({σ }gran}=8.6 % ), power excess width ({σ }width}=8.8 % ), seismically derived stellar mass ({σ }{{m}}=7.8 % ), radius ({σ }{{r}}=2.9 % ), and thus surface gravity ({σ }logg}=0.01 dex). thanks to the large red giant sample, we confirm that red-giant-branch (rgb) and helium-core-burning (heb) stars collectively differ in the distribution of oscillation amplitude, granulation power, and width of power excess, which is mainly due to the mass difference. the distribution of oscillation amplitudes shows an extremely sharp upper edge at fixed {ν }\max , which might hold clues for understanding the excitation and damping mechanisms of the oscillation modes. we find that both oscillation amplitude and granulation power depend on metallicity, causing a spread of 15% in oscillation amplitudes and a spread of 25% in granulation power from [fe/h] = -0.7 to 0.5 dex. our asteroseismic stellar properties can be used as reliable distance indicators and age proxies for mapping and dating galactic stellar populations observed by kepler. they will also provide an excellent opportunity to test asteroseismology using gaia parallaxes, and lift degeneracies in deriving atmospheric parameters in large spectroscopic surveys such as apogee and lamost. | asteroseismology of 16,000 kepler red giants: global oscillation parameters, masses, and radii |
the k2 mission uses the kepler spacecraft to obtain high-precision photometry over ≈80 day campaigns in the ecliptic plane. the ecliptic plane input catalog (epic) provides coordinates, photometry, and kinematics based on a federation of all-sky catalogs to support target selection and target management for the k2 mission. we describe the construction of the epic, as well as modifications and shortcomings of the catalog. kepler magnitudes (kp) are shown to be accurate to ≈0.1 mag for the kepler field, and the epic is typically complete to kp ≈ 17 (kp ≈ 19 for campaigns covered by sloan digital sky survey). we furthermore classify 138,600 targets in campaigns 1-8 (≈88% of the full target sample) using colors, proper motions, spectroscopy, parallaxes, and galactic population synthesis models, with typical uncertainties for g-type stars of ≈3% in {t}{{eff}}, ≈0.3 dex in {log} g, ≈40% in radius, ≈10% in mass, and ≈40% in distance. our results show that stars targeted by k2 are dominated by k-m dwarfs (≈41% of all selected targets), f-g dwarfs (≈36%), and k giants (≈21%), consistent with key k2 science programs to search for transiting exoplanets and galactic archeology studies using oscillating red giants. however, we find significant variation of the fraction of cool dwarfs with galactic latitude, indicating a target selection bias due to interstellar reddening and increased contamination by giant stars near the galactic plane. we discuss possible systematic errors in the derived stellar properties, and differences with published classifications for k2 exoplanet host stars. the epic is hosted at the mikulski archive for space telescopes (mast): http://archive.stsci.edu/k2/epic/search.php. | the k2 ecliptic plane input catalog (epic) and stellar classifications of 138,600 targets in campaigns 1-8 |
in this chapter we review recent advances in understanding the roles that magnetic fields play throughout the star formation process, gained through observations and simulations of molecular clouds, the dense, star-forming phase of the magnetized, turbulent interstellar medium (ism). recent results broadly support a picture in which the magnetic fields of molecular clouds transition from being gravitationally sub-critical and near equipartition with turbulence in low-density cloud envelopes, to being energetically sub-dominant in dense, gravitationally unstable star-forming cores. magnetic fields appear to play an important role in the formation of cloud substructure by setting preferred directions for large-scale gas flows in molecular clouds, and can direct the accretion of material onto star-forming filaments and hubs. low-mass star formation may proceed in environments close to magnetic criticality; high-mass star formation remains less well-understood, but may proceed in more supercritical environments. the interaction between magnetic fields and (proto)stellar feedback may be particularly important in setting star formation efficiency. we also review a range of widely-used techniques for quantifying the dynamic importance of magnetic fields, concluding that better-calibrated diagnostics are required in order to use the spectacular range of forthcoming observations and simulations to quantify our emerging understanding of how magnetic fields influence the outcome of the star formation process. | magnetic fields in star formation: from clouds to cores |
we report 18 dust continuum detections (≥3.3σ) at ~88 and 158 $\mu{\rm m}$ out of 49 ultraviolet (uv)-bright galaxies (muv < -21.3 mag) at $z$ > 6.5, observed by the cycle-7 atacama large millimeter/submillimeter array (alma) large program, reionization-era bright emission line survey (rebels) and its pilot programs. this has more than tripled the number of dust continuum detections known at $z$ > 6.5. out of these 18 detections, 12 are reported for the first time as part of rebels. in addition, 15 of the dust continuum detected galaxies also show a [c ii]$_{\rm 158\,{\rm \mu m}}$ emission line, providing us with accurate redshifts. we anticipate more line emission detections from six targets (including three continuum detected targets) where observations are still ongoing. we estimate that all of the sources have an infrared (ir) luminosity (lir) in a range of $3\!-\!8 \times 10^{11}\, {\rm l_\odot }$, except for one with $l_{\rm ir} = 1.5^{+0.8}_{-0.5} \times 10^{12}\, \, {\rm l_{\odot }}$. their fraction of obscured star formation is significant at ${\gtrsim} 50{{\ \rm per\ cent}}$, despite being uv-selected galaxies. some of the dust continuum detected galaxies show spatial offsets (~0.5-1.5 arcsec) between the rest-uv and far-ir emission peaks. these separations could imply spatially decoupled phases of obscured and unobscured star formation, but a higher spatial resolution observation is required to confirm this. rebels offers the best available statistical constraints on obscured star formation in uv-luminous galaxies at $z$ > 6.5. | the alma rebels survey: dust continuum detections at z > 6.5 |
increasingly, uncertainties in predictions from galaxy formation simulations (at sub-milky way masses) are dominated by uncertainties in stellar evolution inputs. in this paper, we present the full set of updates from the feedback in realistic environment (fire)-2 version of the fire project code, to the next version, fire-3. while the transition from fire-1 to fire-2 focused on improving numerical methods, here we update the stellar evolution tracks used to determine stellar feedback inputs, e.g. stellar mass-loss (o/b and agb), spectra (luminosities and ionization rates), and supernova rates (core-collapse and ia), as well as detailed mass-dependent yields. we also update the low-temperature cooling and chemistry, to enable improved accuracy at $t \lesssim 10^{4}\,$k and densities $n\gg 1\, {\rm cm^{-3}}$, and the meta-galactic ionizing background. all of these synthesize newer empirical constraints on these quantities and updated stellar evolution and yield models from a number of groups, addressing different aspects of stellar evolution. to make the updated models as accessible as possible, we provide fitting functions for all of the relevant updated tracks, yields, etc, in a form specifically designed so they can be directly 'plugged in' to existing galaxy formation simulations. we also summarize the default fire-3 implementations of 'optional' physics, including spectrally resolved cosmic rays and supermassive black hole growth and feedback. | fire-3: updated stellar evolution models, yields, and microphysics and fitting functions for applications in galaxy simulations |
finite size effects in a neutron star merger are manifested, at leading order, through the tidal deformabilities of the stars. if strong first-order phase transitions do not exist within neutron stars, both neutron stars are described by the same equation of state, and their tidal deformabilities are highly correlated through their masses even if the equation of state is unknown. if, however, a strong phase transition exists between the central densities of the two stars, so that the more massive star has a phase transition and the least massive star does not, this correlation will be weakened. in all cases, a minimum deformability for each neutron star mass is imposed by causality, and a less conservative limit is imposed by the unitary gas constraint, both of which we compute. in order to make the best use of gravitational wave data from mergers, it is important to include the correlations relating the deformabilities and the masses as well as lower limits to the deformabilities as a function of mass. focusing on the case without strong phase transitions, and for mergers where the chirp mass m ≤1.4 m⊙, which is the case for all observed double neutron star systems where a total mass has been accurately measured, we show that the ratio of the dimensionless tidal deformabilities satisfy λ1/λ2∼q6, where q =m2/m1 is the binary mass ratio; λ and m are the dimensionless deformability and mass of each star, respectively. moreover, they are bounded by qn-≥λ1/λ2≥qn0 ++q n1 + , where n-<n0 ++q n1 +; the parameters depend only on m , which is accurately determined from the gravitational-wave signal. we also provide analytic expressions for the wider bounds that exist in the case of a strong phase transition. we argue that bounded ranges for λ1/λ2, tuned to m , together with lower bounds to λ (m ), will be more useful in gravitational waveform modeling than other suggested approaches. | tidal deformabilities and neutron star mergers |
spherex is a proposed nasa midex mission selected for phase a study. spherex would carry out the first all-sky spectral survey in the near infrared. at the end of its two-year mission, spherex would obtain 0.75-to-5$\mu$m spectra of every 6.2 arcsec pixel on the sky, with spectral resolution r>35 and a 5-$\sigma$ sensitivity ab$>$19 per spectral/spatial resolution element. more details concerning spherex are available at http://spherex.caltech.edu. the spherex team has proposed three specific science investigations to be carried out with this unique data set: cosmic inflation, interstellar and circumstellar ices, and the extra-galactic background light. though these three themes are undoubtedly compelling, they are far from exhausting the scientific output of spherex. indeed, spherex would create a unique all-sky spectral database including spectra of very large numbers of astronomical and solar system targets, including both extended and diffuse sources. these spectra would enable a wide variety of investigations, and the spherex team is dedicated to making the data available to the community to enable these investigations, which we refer to as legacy science. to that end, we have sponsored two workshops for the general scientific community to identify the most interesting legacy science themes and to ensure that the spherex data products are responsive to their needs. in february of 2016, some 50 scientists from all fields met in pasadena to develop these themes and to understand their implications for the spherex mission. the 2016 workshop highlighted many synergies between spherex and other contemporaneous astronomical missions, facilities, and databases. consequently, in january 2018 we convened a second workshop at the center for astrophysics in cambridge to focus specifically on these synergies. this white paper reports on the results of the 2018 spherex workshop. | science impacts of the spherex all-sky optical to near-infrared spectral survey ii: report of a community workshop on the scientific synergies between the spherex survey and other astronomy observatories |
neutrinos are known to play important roles in many astrophysical scenarios from the early period of the big bang to current stellar evolution being a unique messenger of the fusion reactions occurring in the center of our sun. in particular, neutrinos are crucial in determining the dynamics and the composition evolution in explosive events such as core-collapse supernovae and the merger of two neutron stars. in this paper, we review the current understanding of supernovae and binary neutron star mergers by focusing on the role of neutrinos therein. several recent improvements on the theoretical modeling of neutrino interaction rates in nuclear matter as well as their impact on the heavy element nucleosynthesis in the supernova neutrino-driven wind are discussed, including the neutrino-nucleon opacity at the mean field level taking into account the relativistic kinematics of nucleons, the effect due to the nucleon-nucleon correlation, and the nucleon-nucleon bremsstrahlung. we also review the framework used to compute the neutrino-nucleus interactions and the up-to-date yield prediction for isotopes from neutrino nucleosynthesis occurring in the outer envelope of the supernova progenitor star during the explosion. here improved predictions of energy spectra of supernova neutrinos of all flavors have had significant impact on the nucleosynthesis yields. rapid progresses in modeling the flavor oscillations of neutrinos in these environments, including several novel mechanisms for collective neutrino oscillations and their potential impacts on various nucleosynthesis processes are summarized. | neutrinos and nucleosynthesis of elements |
we present pipe3d, an analysis pipeline based on the fit3d fitting tool, developed to explore the properties of the stellar populations and ionized gas of integral field spectroscopy (ifs) data. pipe3d was created to provide coherent, simple to distribute, and comparable dataproducts, independently of the origin of the data, focused on the data of the most recent ifu surveys (e.g., califa, manga, and sami), and the last generation ifs instruments (e.g., muse). in this article we describe the different steps involved in the analysis of the data, illustrating them by showing the dataproducts derived for ngc 2916, observed by califa and p-manga. as a practical example of the pipeline we present the complete set of dataproducts derived for the 200 datacubes that comprises the v500 setup of the califa data release 2 (dr2), making them freely available through the network. finally, we explore the hypothesis that the properties of the stellar populations and ionized gas of galaxies at the effective radius are representative of the overall average ones, finding that this is indeed the case. | pipe3d, a pipeline to analyze integral field spectroscopy data: ii. analysis sequence and califa dataproducts |
we present a large spectroscopic campaign with keck/multi-object spectrometer for infrared exploration (mosfire) targeting lyα emission (lyα) from intrinsically faint lyman-break galaxies (lbgs) behind 12 efficient galaxy cluster lenses. gravitational lensing allows us to probe the more abundant faint galaxy population to sensitive lyα equivalent-width limits. during the campaign, we targeted 70 lbg candidates with the mosfire y band, selected photometrically to cover lyα over the range 7 < z < 8.2. we detect signal-to-noise ratio > 5 emission lines in two of these galaxies and find that they are likely lyα at z = 7.148 ± 0.001 and z = 7.161 ± 0.001. we present new lens models for four of the galaxy clusters, using our previously published lens models for the remaining clusters to determine the magnification factors for the source galaxies. using a bayesian framework that employs large-scale reionization simulations of the intergalactic medium (igm) as well as realistic properties of the interstellar medium and circumgalactic medium, we infer the volume-averaged neutral hydrogen fraction, {\overline{x}}{{h}{{i}}}, in the igm during reionization to be {\overline{x}}{{h}{{i}}}={0.88}-0.10+0.05 at z = 7.6 ± 0.6. our result is consistent with a late and rapid reionization scenario inferred by planck. | constraining the neutral fraction of hydrogen in the igm at redshift 7.5 |
recent data from the james webb space telescope allow a first glimpse of galaxies at z ≳ 11. the most successful tool for identifying ultra-high-redshift candidates and inferring their properties is photometric template fitting. however, current methods rely on templates derived from much lower-redshift conditions, including stellar populations older than the age of the universe at z > 12, a stellar initial mass function that is physically disallowed at z > 6, and weaker emission lines than currently observed at z > 7.5. here, two sets of synthetic templates, optimized for the expected astrophysics of galaxies at 8 < z < 12 and z > 12, are developed and used to fit three galaxies at z > 12 from the smacs0723 field. using these improved templates, quantitative estimates are produced of the bias in inferred properties from jwst observations at z > 8 due to these effects. the best-fit redshifts are similar to those found with previous template sets, but the inferred stellar masses drop by as much as 1-1.6 dex, such that stellar masses are no longer seemingly inconsistent with λcdm. the two new template sets are released in formats compatible with eazy and lephare. | templates for fitting photometry of ultra-high-redshift galaxies |
cosmic dust is an essential component shaping both the evolution of galaxies and their observational signatures. how quickly dust builds up in the early universe remains an open question that requires deep observations at (sub-)millimetre wavelengths to resolve. here, we use atacama large millimeter array observations of 45 galaxies from the reionization era bright emission line survey (rebels) and its pilot programs, designed to target [c ii] and dust emission in uv-selected galaxies at z ~ 7, to investigate the dust content of high-redshift galaxies through a stacking analysis. we find that the typical fraction of obscured star formation fobs = sfrir/sfruv+ir depends on stellar mass, similar to what is observed at lower redshift, and ranges from fobs ≈ 0.3 - 0.6 for galaxies with log10(m⋆/m⊙) = 9.4-10.4. we further adopt the z ~ 7 stellar mass function from the literature to extract the obscured cosmic star formation rate density (sfrd) from the rebels survey. our results suggest only a modest decrease in the sfrd between 3 ≲ z ≲ 7, with dust-obscured star formation still contributing ${\sim}30{{\ \rm per\ cent}}$ at z ~ 7. while we extensively discuss potential caveats, our analysis highlights the continued importance of dust-obscured star formation even well into the epoch of reionization. | the alma rebels survey: the dust-obscured cosmic star formation rate density at redshift 7 |
the [c ii] 158 μm line is one of the strongest ir emission lines, which has been shown to trace the star formation rate (sfr) of galaxies in the nearby universe, and up to z ∼ 2. whether this is also the case at higher redshift and in the early universe remains debated. the alpine survey, which targeted 118 star-forming galaxies at 4.4 < z < 5.9, provides a new opportunity to examine this question with the first statistical dataset. using the alpine data and earlier measurements from the literature, we examine the relation between the [c ii] luminosity and the sfr over the entire redshift range from z ∼ 4 - 8. alpine galaxies, which are both detected in [c ii] and in dust continuum, show good agreement with the local l([cii])-sfr relation. galaxies undetected in the continuum by alma are found to be over-luminous in [c ii] when the uv sfr is used. after accounting for dust-obscured star formation, by an amount of sfr(ir) ≈ sfr(uv) on average, which results from two different stacking methods and sed fitting, the alpine galaxies show an l([cii])-sfr relation comparable to the local one. when [c ii] non-detections are taken into account, the slope may be marginally steeper at high-z, although this is still somewhat uncertain. when compared homogeneously, the z > 6 [c ii] measurements (detections and upper limits) do not behave very differently to the z ∼ 4 - 6 data. we find a weak dependence of l([cii])/sfr on the lyα equivalent width. finally, we find that the ratio l([cii])/lir ∼ (1 - 3) × 10-3 for the alpine sources, comparable to that of "normal" galaxies at lower redshift. our analysis, which includes the largest sample (∼150 galaxies) of [c ii] measurements at z > 4 available so far, suggests no or little evolution of the [c ii]-sfr relation over the last 13 gyr of cosmic time. | the alpine-alma [c ii] survey. little to no evolution in the [c ii]-sfr relation over the last 13 gyr |
we show that a black-hole binary with an external companion can undergo lidov-kozai cycles that cause a close pericenter passage, leading to a rapid merger due to gravitational-wave emission. this scenario occurs most often for systems in which the companion has a mass comparable to the reduced mass of the binary and the companion orbit has a semimajor axis within a factor of ∼10 of the binary semimajor axis. using a simple population-synthesis model and three-body simulations, we estimate the rate of mergers in triple black-hole systems in the field to be about six per gpc3 per year in the absence of natal kicks during black-hole formation. this value is within the low end of the 90% credible interval for the total black hole-black hole merger rate inferred from the current ligo results. there are many uncertainties in these calculations, the largest of which is the unknown distribution of natal kicks. even modest natal kicks of 40 km s-1 will reduce the merger rate by a factor of 40. a few percent of these systems will have eccentricity greater than 0.999 when they first enter the frequency band detectable by aligo (above 10 hz). | lidov-kozai cycles with gravitational radiation: merging black holes in isolated triple systems |
the recent release of the second gravitational-wave transient catalog (gwtc-2) has increased significantly the number of known gw events, enabling unprecedented constraints on formation models of compact binaries. one pressing question is to understand the fraction of binaries originating from different formation channels, such as isolated field formation versus dynamical formation in dense stellar clusters. in this paper, we combine the cosmic binary population synthesis suite and the cmc code for globular cluster evolution to create a mixture model for black hole binary formation under both formation scenarios. for the first time, these code bodies are combined self-consistently, with cmc itself employing cosmic to track stellar evolution. we then use a deep-learning enhanced hierarchical bayesian analysis to continuously sample over and constrain the common envelope efficiency α assumed in cosmic, the initial cluster virial radius rv adopted in cmc, and the intrinsic mixture fraction f between each channel. under specific assumptions about other uncertain aspects of isolated binary and globular cluster evolution, we report the median and 90% confidence interval of three physical parameters for the intrinsic population (f ,α ,rv)=(0.20-0.18+0.32,2.26-1.84+2.65,2.71-1.17+0.83) . this simultaneous constraint agrees with observed properties of globular clusters in the milky way and is an important first step in the pathway toward learning the astrophysics of compact binary formation through gw observations. | joint constraints on the field-cluster mixing fraction, common envelope efficiency, and globular cluster radii from a population of binary hole mergers via deep learning |
gw170817 is the very first observation of gravitational waves originating from the coalescence of two compact objects in the mass range of neutron stars, accompanied by electromagnetic counterparts, and offers an opportunity to directly probe the internal structure of neutron stars. we perform bayesian model selection on a wide range of theoretical predictions for the neutron star equation of state. for the binary neutron star hypothesis, we find that we cannot rule out the majority of theoretical models considered. in addition, the gravitational-wave data alone does not rule out the possibility that one or both objects were low-mass black holes. we discuss the possible outcomes in the case of a binary neutron star merger, finding that all scenarios from prompt collapse to long-lived or even stable remnants are possible. for long-lived remnants, we place an upper limit of 1.9 khz on the rotation rate. if a black hole was formed any time after merger and the coalescing stars were slowly rotating, then the maximum baryonic mass of non-rotating neutron stars is at most [ image ], and three equations of state considered here can be ruled out. we obtain a tighter limit of [ image ] for the case that the merger results in a hypermassive neutron star. | model comparison from ligo-virgo data on gw170817's binary components and consequences for the merger remnant |
we report a quantum monte carlo calculation of the equation of state of symmetric nuclear matter using local interactions derived from chiral effective field theory up to next-to-next-to-leading order fit to few-body observables only. the empirical saturation density and energy are well reproduced within statistical and systematic uncertainties. we have also derived the symmetry energy as a function of the density, finding good agreement with available experimentally derived constraints at saturation and twice saturation density. we find that the corresponding pressure is also in excellent agreement with recent constraints extracted from gravitational waves of the neutron-star merger gw170817 by the ligo-virgo detection. | nuclear and neutron-star matter from local chiral interactions |
the δ-isobar degrees of freedom are included in the covariant density functional (cdf) theory to study the equation of state (eos) and composition of dense matter in compact stars. in addition to δ's we include the full octet of baryons, which allows us to study the interplay between the onset of delta isobars and hyperonic degrees of freedom. using both the hartree and hartree-fock approximation we find that δ's appear already at densities slightly above the saturation density of nuclear matter for a wide range of the meson-δ coupling constants. this delays the appearance of hyperons and significantly affects the gross properties of compact stars. specifically, δ's soften the eos at low densities but stiffen it at high densities. this softening reduces the radius of a canonical 1.4m⊙ star by up to 2 km for a reasonably attractive δ potential in matter, while the stiffening results in larger maximum masses of compact stars. we conclude that the hypernuclear cdf parametrizations that satisfy the 2m⊙ maximum mass constraint remain valid when δ isobars are included, with the important consequence that the resulting stellar radii are shifted toward lower values, which is in agreement with the analysis of neutron star radii. | competition between delta isobars and hyperons and properties of compact stars |
we use high-resolution simulations of isolated dwarf galaxies to study the physics of dark matter cusp-core transformations at the edge of galaxy formation: m200 = 107-109 m⊙. we work at a resolution (∼4 pc minimum cell size; ∼250 m⊙ per particle) at which the impact from individual supernovae explosions can be resolved, becoming insensitive to even large changes in our numerical `sub-grid' parameters. we find that our dwarf galaxies give a remarkable match to the stellar light profile; star formation history; metallicity distribution function; and star/gas kinematics of isolated dwarf irregular galaxies. our key result is that dark matter cores of size comparable to the stellar half-mass radius r1/2 always form if star formation proceeds for long enough. cores fully form in less than 4 gyr for the m200 = 108 m⊙ and ∼14 gyr for the 109 m⊙ dwarf. we provide a convenient two parameter `corenfw' fitting function that captures this dark matter core growth as a function of star formation time and the projected stellar half-mass radius. our results have several implications: (i) we make a strong prediction that if λcold dark matter is correct, then `pristine' dark matter cusps will be found either in systems that have truncated star formation and/or at radii r > r1/2; (ii) complete core formation lowers the projected velocity dispersion at r1/2 by a factor of ∼2, which is sufficient to fully explain the `too-big-to-fail problem'; and (iii) cored dwarfs will be much more susceptible to tides, leading to a dramatic scouring of the sub-halo mass function inside galaxies and groups. | dark matter cores all the way down |
merging neutron stars produce "kilonovae"-electromagnetic transients powered by the decay of unstable nuclei synthesized via rapid neutron capture (the r-process) in material that is gravitationally unbound during inspiral and coalescence. kilonova emission, if accurately interpreted, can be used to characterize the masses and compositions of merger-driven outflows, helping to resolve a long-standing debate about the origins of r-process material in the universe. we explore how the uncertain properties of nuclei involved in the r-process complicate the inference of outflow properties from kilonova observations. using r-process simulations, we show how nuclear physics uncertainties impact predictions of radioactive heating and element synthesis. for a set of models that span a large range in both predicted heating and final abundances, we carry out detailed numerical calculations of decay product thermalization and radiation transport in a kilonova ejecta with a fixed mass and density profile. the light curves associated with our models exhibit great diversity in their luminosities, with peak brightness varying by more than an order of magnitude. we also find variability in the shape of the kilonova light curves and their color, which in some cases runs counter to the expectation that increasing levels of lanthanide and/or actinide enrichment will be correlated with longer, dimmer, redder emission. | kilonovae across the nuclear physics landscape: the impact of nuclear physics uncertainties on r-process-powered emission |
axion-like particle (alp) dark matter shows distinctive behavior on scales where wavelike effects dominate over self-gravity. ultralight axions are candidates for fuzzy dark matter (fdm) whose de broglie wavelength in virialized halos reaches scales of kiloparsecs. important features of fdm scenarios are the formation of solitonic halo cores, suppressed small-scale perturbations, and enhanced gravitational relaxation. more massive alps, including the qcd axion, behave like cdm on galactic scales but may be clumped into axion miniclusters if they were produced after inflation. just as fdm halos, axion miniclusters may host the formation of coherent bound objects (axion stars) by bose-einstein condensation. this article presents a selection of topics in this field that are currently under active investigation. | small-scale structure of fuzzy and axion-like dark matter |
we present keck-mosfire h and k spectra for a sample of 24 candidate quiescent galaxies at 3 < z < 4, identified from their rest-frame uvj colors and photometric redshifts in the zfourge and 3dhst surveys. with median integration times of one hour in h and five in k, we obtain spectroscopic redshifts for half of the sample, using either balmer absorption lines or nebular emission lines. we confirm the high accuracy of the photometric redshifts for this spectroscopically-confirmed sample, with a median |zphot - zspec|/(1 + zspec) of 1.2%. two galaxies turn out to be dusty hα emitters at lower redshifts (z < 2.5), and these are the only two detected in the sub-mm with alma. high equivalent-width [o iii] emission is observed in two galaxies, contributing up to 30% of the k-band flux and mimicking the uvj colors of an old stellar population. this implies a failure rate of only 20% for the uvj selection at these redshifts. lastly, balmer absorption features are identified in four galaxies, among the brightest of the sample, confirming the absence of ob stars. we then modeled the spectra and photometry of all quiescent galaxies with a wide range of star-formation histories. we find specific star-formation rates (ssfr) lower than 0.15 gyr-1 (a factor of ten below the main sequence) for all but one galaxy, and lower than 0.01 gyr-1 for half of the sample. these values are consistent with the observed hβ and [o ii] luminosities, and the alma non-detections. the implied formation histories reveal that these galaxies have quenched on average 300 myr prior to being observed, between z = 3.5 and 5, and that half of their stars were formed by z ∼ 5.5 with a mean sfr 300 m⊙ yr-1. we finally compared the uvj selection to a selection based instead on the ssfr, as measured from the photometry. we find that galaxies a factor of ten below the main sequence are 40% more numerous than uvj-selected quiescent galaxies, implying that the uvj selection is pure but incomplete. current models fail at reproducing our observations, and underestimate either the number density of quiescent galaxies by more than an order of magnitude, or the duration of their quiescence by a factor two. overall, these results confirm the existence of an unexpected population of quiescent galaxies at z > 3, and offer the first insights on their formation histories. tables 3 and a.4 are also available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/618/a85 | near infrared spectroscopy and star-formation histories of 3 ≤ z ≤ 4 quiescent galaxies |
we present the characterization of the main properties of a sample of 98 agn host galaxies, both type-ii and type-i, in comparison with those of ≈2700 non-active galaxies observed by the manga survey. we found that agn hosts are morphologically early-type or early-spirals. agn hosts are, on average, more massive, more compact, more centrally peaked and more pressure-supported systems. they are located in the intermediate/transition region between starforming and non-star-forming galaxies (i.e., the so-called green valley). we consider that they are in the process of halting/quenching the star formation. the analysis of the radial distributions of different properties shows that the quenching happens from inside-out involving both a decrease of the effciency of the star formation and a deficit of molecular gas. the data-products of the current analysis are distributed as a value added catalog within the sdss-dr14. | sdss iv manga - properties of agn host galaxies |
accurate and fast gravitational waveform (gw) models are essential to extract information about the properties of compact binary systems that generate gws. building on previous work, we present an extension of the nrtidal model for binary neutron star (bns) waveforms. the upgrades are (i) a new closed-form expression for the tidal contribution to the gw phase which includes further analytical knowledge and is calibrated to more accurate numerical relativity data than previously available; (ii) a tidal correction to the gw amplitude; and (iii) an extension of the spin-sector incorporating equation-of-state-dependent finite size effects at quadrupolar and octupolar order; these appear in the spin-spin tail terms and cubic-in-spin terms, both at 3.5 pn. we add the new description to the precessing binary black hole waveform model imrphenompv2 to obtain a frequency-domain precessing binary neutron star model. in addition, we extend the seobnrv4_rom and imrphenomd aligned-spin binary black hole waveform models with the improved tidal phase corrections. focusing on the new imrphenompv2_nrtidalv2 approximant, we test the model by comparing with numerical relativity waveforms as well as hybrid waveforms combining tidal effective-one-body and numerical relativity data. we also check consistency against a tidal effective-one-body model across large regions of the bns parameter space. | improving the nrtidal model for binary neutron star systems |
the phenomenon of quasi-periodic pulsations (qpps) in solar and stellar flares has been known for over 50 years and significant progress has been made in this research area. it has become clear that qpps are not rare—they are found in many flares and, therefore, robust flare models should reproduce their properties in a natural way. at least fifteen mechanisms/models have been developed to explain qpps in solar flares, which mainly assume the presence of magnetohydrodynamic (mhd) oscillations in coronal structures (magnetic loops and current sheets) or quasi-periodic regimes of magnetic reconnection. we review the most important and interesting results on flare qpps, with an emphasis on the results of recent years, and we present the predicted and prominent observational signatures of each of the fifteen mechanisms. however, it is not yet possible to draw an unambiguous conclusion as to the correct underlying qpp mechanism because of the qualitative, rather than quantitative, nature of most of the models and also due to insufficient observational information on the physical properties of the flare region, in particular the spatial structure of the qpp source. we also review qpps in stellar flares, where progress is largely based on solar-stellar analogies, suggesting similarities in the physical processes in flare regions on the sun and magnetoactive stars. the presence of qpps with similar properties in solar and stellar flares is, in itself, a strong additional argument in favor of the likelihood of solar-stellar analogies. hence, advancing our understanding of qpps in solar flares provides an important additional channel of information about stellar flares. however, further work in both theory/simulations and in observations is needed. | quasi-periodic pulsations in solar and stellar flares: a review of underpinning physical mechanisms and their predicted observational signatures |
we report our observation of the short gamma-ray burst (grb) grb 170817a, associated to the binary neutron star merger gravitational wave (gw) event gw 170817, performed in the x-ray band with xmm-newton 135 d after the event (on 29 december, 2017). we find evidence for a flattening of the x-ray light curve with respect to the previously observed brightening. this is also supported by a nearly simultaneous optical hubble space telescope observation and successive x-ray chandra and low-frequency radio observations recently reported in the literature. since the optical-to-x-ray spectral slope did not change with respect to previous observations, we exclude that the change in the temporal evolution of the light curve is due to the passage of the cooling frequency: its origin must be geometric or dynamical. we interpret all the existing afterglow data with two models: i) a structured jet and ii) a jet-less isotropic fireball with some stratification in its radial velocity structure. both models fit the data and predict that the radio flux must decrease simultaneously with the optical and x-ray emission, making it difficult to distinguish between them at the present stage. polarimetric measurements and the rate of short grb-gw associations in future ligo/virgo runs will be key to disentangle these two geometrically different scenarios. | the evolution of the x-ray afterglow emission of gw 170817/ grb 170817a in xmm-newton observations |
observational evidence points to a red supergiant (rsg) progenitor for sn 2023ixf. the progenitor candidate has been detected in archival images at wavelengths (≥0.6 μm) where rsgs typically emit profusely. this object is distinctly variable in the infrared (ir). we characterize the variability using pre-explosion mid-ir (3.6 and 4.5 μm) spitzer and ground-based near-ir (jhks ) archival data jointly covering 19 yr. the ir light curves exhibit significant variability with rms amplitudes in the range 0.2-0.4 mag, increasing with decreasing wavelength. from a robust period analysis of the more densely sampled spitzer data, we measure a period of 1091 ± 71 days. we demonstrate using gaussian process modeling that this periodicity is also present in the near-ir light curves, thus indicating a common physical origin, which is likely pulsational instability. we use a period-luminosity relation for rsgs to derive a value of mk= -11.58 ± 0.31 mag. assuming a late m spectral type, this corresponds to $\mathrm{log}(l/{l}_{\odot })=5.27\pm 0.12$ at t eff = 3200 k and to $\mathrm{log}(l/{l}_{\odot })=5.37\pm 0.12$ at t eff = 3500 k. this gives an independent estimate of the progenitor's luminosity, unaffected by uncertainties in extinction and distance. assuming the progenitor candidate underwent enhanced dust-driven mass loss during the time of these archival observations, and using an empirical period-luminosity-based mass-loss prescription, we obtain a mass-loss rate of around (2-4) × 10-4 m ⊙ yr-1. comparing the above luminosity with stellar evolution models, we infer an initial mass for the progenitor candidate of 20 ± 4 m ⊙, making this one of the most massive progenitors for a type ii sn detected to date. | the sn 2023ixf progenitor in m101. i. infrared variability |
metamodeling for the nucleonic equation of state (eos), inspired from a taylor expansion around the saturation density of symmetric nuclear matter, is proposed and parameterized in terms of the empirical parameters. the present knowledge of nuclear empirical parameters is first reviewed in order to estimate their average values and associated uncertainties, and thus defining the parameter space of the metamodeling. they are divided into isoscalar and isovector types, and ordered according to their power in the density expansion. the goodness of the metamodeling is analyzed against the predictions of the original models. in addition, since no correlation among the empirical parameters is assumed a priori, all arbitrary density dependences can be explored, which might not be accessible in existing functionals. spurious correlations due to the assumed functional form are also removed. this meta-eos allows direct relations between the uncertainties on the empirical parameters and the density dependence of the nuclear equation of state and its derivatives, and the mapping between the two can be done with standard bayesian techniques. a sensitivity analysis shows that the more influential empirical parameters are the isovector parameters lsym and ksym, and that laboratory constraints at supersaturation densities are essential to reduce the present uncertainties. the present metamodeling for the eos for nuclear matter is proposed for further applications in neutron stars and supernova matter. | equation of state for dense nucleonic matter from metamodeling. i. foundational aspects |
we present a new moment-based energy-integrated neutrino transport code for neutron star merger simulations in general relativity. in the merger context, ours is the first code to include doppler effects at all orders in υ/c, retaining all non-linear neutrino-matter coupling terms. the code is validated with a stringent series of tests. we show that the inclusion of full neutrino-matter coupling terms is necessary to correctly capture the trapping of neutrinos in relativistically moving media, such as in differentially rotating merger remnants. we perform preliminary simulations proving the robustness of the scheme in simulating ab-initio mergers to black hole collapse and long-term neutron star remnants up to ${\sim }70\,$ ms. the latter is the longest dynamical space-time, 3d, general relativistic simulations with full neutrino transport to date. we compare results obtained at different resolutions and using two different closures for the moment scheme. we do not find evidences of significant out-of-thermodynamic equilibrium effects, such as bulk viscosity, on the post-merger dynamics or gravitational wave emission. neutrino luminosities and average energies are in good agreement with theory expectations and previous simulations by other groups using similar schemes. we compare dynamical and early wind ejecta properties obtained with m1 and with our older neutrino treatment. we find that the m1 results have systematically larger proton fractions. however, the differences in the nucleosynthesis yields are modest. this work sets the basis for future detailed studies spanning a wider set of neutrino reactions, binaries, and equations of state. | a new moment-based general-relativistic neutrino-radiation transport code: methods and first applications to neutron star mergers |
the dark energy spectroscopic instrument (desi) survey is a spectroscopic survey of tens of millions of galaxies at 0 < z < 3.5 covering 14,000 sq. deg. of the sky. in its first 1.1 yr of survey operations, it has observed more than 14 million galaxies and 4 million stars. we describe the processes that govern desi's observations of the 15,000 fields composing the survey. this includes the planning of each night's observations in the afternoon; automatic selection of fields to observe during the night; real-time assessment of field completeness on the basis of observing conditions during each exposure; reduction, redshifting, and quality assurance of each field of targets in the morning following observation; and updates to the list of future targets to observe on the basis of these results. we also compare the performance of the survey with historical expectations and find good agreement. simulations of the weather and of desi observations using the real field-selection algorithm show good agreement with the actual observations. after accounting for major unplanned shutdowns, the dark time survey is progressing about 7% faster than forecast, which is good agreement given approximations made in the simulations. | survey operations for the dark energy spectroscopic instrument |
we present epic variability extraction and removal for exoplanet science targets (everest), an open-source pipeline for removing instrumental noise from k2 light curves. everest employs a variant of pixel level decorrelation to remove systematics introduced by the spacecraft’s pointing error and a gaussian process to capture astrophysical variability. we apply everest to all k2 targets in campaigns 0-7, yielding light curves with precision comparable to that of the original kepler mission for stars brighter than {k}p≈ 13, and within a factor of two of the kepler precision for fainter targets. we perform cross-validation and transit injection and recovery tests to validate the pipeline, and compare our light curves to the other de-trended light curves available for download at the mast high level science products archive. we find that everest achieves the highest average precision of any of these pipelines for unsaturated k2 stars. the improved precision of these light curves will aid in exoplanet detection and characterization, investigations of stellar variability, asteroseismology, and other photometric studies. the everest pipeline can also easily be applied to future surveys, such as the tess mission, to correct for instrumental systematics and enable the detection of low signal-to-noise transiting exoplanets. the everest light curves and the source code used to generate them are freely available online. | everest: pixel level decorrelation of k2 light curves |
fast radio bursts (frbs) are millisecond-duration flashes of radio waves that are visible at distances of billions of light years1. the nature of their progenitors and their emission mechanism remain open astrophysical questions2. here we report the detection of the multicomponent frb 20191221a and the identification of a periodic separation of 216.8(1) ms between its components, with a significance of 6.5σ. the long (roughly 3 s) duration and nine or more components forming the pulse profile make this source an outlier in the frb population. such short periodicity provides strong evidence for a neutron-star origin of the event. moreover, our detection favours emission arising from the neutron-star magnetosphere3,4, as opposed to emission regions located further away from the star, as predicted by some models5. | sub-second periodicity in a fast radio burst |
we present the “sins/zc-sinf ao survey” of 35 star-forming galaxies, the largest sample with deep adaptive optics (ao)-assisted near-infrared integral field spectroscopy at z ∼ 2. the observations, taken with sinfoni at the very large telescope, resolve the hα and [n ii] emission and kinematics on scales of ∼1.5 kpc. the sample probes the massive (m ⋆ ∼ 2 × 109 - 3 × 1011 m ⊙), actively star-forming (sfr ∼ 10-600 m ⊙ yr-1) part of the z ∼ 2 galaxy population over a wide range of colors ((u - v)rest ∼ 0.15-1.5 mag) and half-light radii (re,h∼ 1-8.5 kpc). the sample overlaps largely with the “main sequence” of star-forming galaxies in the same redshift range to a similar k ab = 23 mag limit; it has ∼0.3 dex higher median specific sfr, ∼0.1 mag bluer median (u - v)rest color, and ∼10% larger median rest-optical size. we describe the observations, data reduction, and extraction of basic flux and kinematic properties. with typically 3-4 times higher resolution and 4-5 times longer integrations (up to 23 hr) than the seeing-limited data sets of the same objects, the ao data reveal much more detail in morphology and kinematics. the complete ao observations confirm the majority of kinematically classified disks and the typically elevated disk velocity dispersions previously reported based on subsets of the data. we derive typically flat or slightly negative radial [n ii]/{{h}}α gradients, with no significant trend with global galaxy properties, kinematic nature, or the presence of an agn. azimuthal variations in [n ii]/{{h}}α are seen in several sources and are associated with ionized gas outflows and possibly more metal-poor star-forming clumps or small companions. the reduced ao data are made publicly available (http://www.mpe.mpg.de/ir/sins/sins-zcsinf-data). based on observations obtained at the very large telescope of the european southern observatory, paranal, chile (eso programme ids 075.a-0466, 076.a-0527, 079.a-0341, 080.a-0330, 080.a-0339, 080.a-0635, 081.b-0568, 081.a-0672, 082.a-0396, 183.a-0781, 087.a-0081, 088.a-0202, 088.a-0209, 091.a-0126). | the sins/zc-sinf survey of z ∼ 2 galaxy kinematics: sinfoni adaptive optics-assisted data and kiloparsec-scale emission-line properties |
the subaru coronagraphic extreme adaptive optics (scexao) instrument is a multipurpose high-contrast imaging platform designed for the discovery and detailed characterization of exoplanetary systems and serves as a testbed for high-contrast imaging technologies for elts. it is a multi-band instrument which makes use of light from 600 to 2500nm allowing for coronagraphic direct exoplanet imaging of the inner 3 lambda/d from the stellar host. wavefront sensing and control are key to the operation of scexao. a partial correction of low-order modes is provided by subaru's facility adaptive optics system with the final correction, including high-order modes, implemented downstream by a combination of a visible pyramid wavefront sensor and a 2000-element deformable mirror. the well corrected nir (y-k bands) wavefronts can then be injected into any of the available coronagraphs, including but not limited to the phase induced amplitude apodization and the vector vortex coronagraphs, both of which offer an inner working angle as low as 1 lambda/d. non-common path, low-order aberrations are sensed with a coronagraphic low-order wavefront sensor in the infrared (ir). low noise, high frame rate, nir detectors allow for active speckle nulling and coherent differential imaging, while the hawaii 2rg detector in the hiciao imager and/or the charis integral field spectrograph (from mid 2016) can take deeper exposures and/or perform angular, spectral and polarimetric differential imaging. science in the visible is provided by two interferometric modules: vampires and first, which enable sub-diffraction limited imaging in the visible region with polarimetric and spectroscopic capabilities respectively. we describe the instrument in detail and present preliminary results both on-sky and in the laboratory. | the subaru coronagraphic extreme adaptive optics system: enabling high-contrast imaging on solar-system scales |
we present a detailed analysis of the rest-frame optical emission line ratios for three spectroscopically confirmed galaxies at z > 7.5. the galaxies were identified in the james webb space telescope (jwst) early release observations field smacs j0723.3 - 7327. by quantitatively comparing balmer and oxygen line ratios of these galaxies with various low-redshift 'analogue' populations (e.g. green peas, blueberries, etc.), we show that no single analogue population captures the diversity of line ratios of all three galaxies observed at z > 7.5. we find that s06355 at z = 7.67 and s10612 at z = 7.66 are similar to local green peas and blueberries. in contrast, s04590 at z = 8.50 appears to be significantly different from the other two galaxies, most resembling extremely low-metallicity systems in the local universe. perhaps the most striking spectral feature in s04590 is the curiously high [o iii] λ4363/[o iii] λ5007 ratio (ro3) of 0.048 (or 0.055 when dust-corrected), implying either extremely high electron temperatures, >3 × 104 k, or gas densities >104 cm-3. observed line ratios indicate that this galaxy is unlikely to host an agn. using photoionization modelling, we show that the inclusion of high-mass x-ray binaries or a high cosmic ray background in addition to a young, low-metallicity stellar population can provide the additional heating necessary to explain the observed high ro3 while remaining consistent with other observed line ratios. our models represent a first step at accurately characterizing the dominant sources of photoionization and heating at very high redshifts, demonstrating that non-thermal processes may become important as we probe deeper into the epoch of reionization. | first insights into the ism at z > 8 with jwst: possible physical implications of a high [o iii] λ4363/[o iii] λ5007 |
we present new observations of the binary neutron star merger gw170817 at δt ≈ 220-290 days post-merger, at radio (karl g. jansky very large array; vla), x-ray (chandra x-ray observatory), and optical (hubble space telescope; hst) wavelengths. these observations provide the first evidence for a turnover in the x-ray light curve, mirroring a decline in the radio emission at ≳5σ significance. the radio-to-x-ray spectral energy distribution exhibits no evolution into the declining phase. our full multi-wavelength data set is consistent with the predicted behavior of our previously published models of a successful structured jet expanding into a low-density circumbinary medium, but pure cocoon models with a choked jet cannot be ruled out. if future observations continue to track our predictions, we expect that the radio and x-ray emission will remain detectable until ∼1000 days post-merger. | a decline in the x-ray through radio emission from gw170817 continues to support an off-axis structured jet |
a binary neutron star merger has been observed in a multi-messenger detection of gravitational wave (gw) and electromagnetic (em) radiation. binary neutron stars that merge within a hubble time, as well as many other compact binaries, are expected to form via common envelope evolution. yet five decades of research on common envelope evolution have not yet resulted in a satisfactory understanding of the multi-spatial multi-timescale evolution for the systems that lead to compact binaries. in this paper, we report on the first successful simulations of common envelope ejection leading to binary neutron star formation in 3d hydrodynamics. we simulate the dynamical inspiral phase of the interaction between a 12$m_\odot$ red supergiant and a 1.4$m_\odot$ neutron star for different initial separations and initial conditions. for all of our simulations, we find complete envelope ejection and final orbital separations of $a_{\rm f} \approx 1.3$-$5.1 r_\odot$ depending on the simulation and criterion, leading to binary neutron stars that can merge within a hubble time. we find $\alpha_{\rm ce}$-equivalent efficiencies of $\approx 0.1$-$2.7$ depending on the simulation and criterion, but this may be specific for these extended progenitors. we fully resolve the core of the star to $\lesssim 0.005 r_\odot$ and our 3d hydrodynamics simulations are informed by an adjusted 1d analytic energy formalism and a 2d kinematics study in order to overcome the prohibitive computational cost of simulating these systems. the framework we develop in this paper can be used to simulate a wide variety of interactions between stars, from stellar mergers to common envelope episodes leading to gw sources. | successful common envelope ejection and binary neutron star formation in 3d hydrodynamics |
we present evidence for localized deviations from keplerian rotation, i.e., velocity "kinks," in 8 of the 18 circumstellar disks observed by the dsharp program: doar 25, elias 2-27, gw lup, hd 143006, hd 163296, im lup, sz 129, and waoph 6. most of the kinks are detected over a small range in both radial extent and velocity, suggesting a planetary origin, but for some of them foreground contamination prevents us from measuring their spatial and velocity extent. because of the dsharp limited spectral resolution and signal to noise in the 12co j = 2-1 line, as well as cloud contamination, the kinks are usually detected in only one spectral channel, and will require confirmation. the strongest circumstantial evidence for protoplanets in the absence of higher spectral resolution data and additional tracers is that, upon deprojection, we find that all of the candidate planets lie within a gap and/or at the end of a spiral detected in dust continuum emission. this suggests that a significant fraction of the dust gaps and spirals observed by atacama large millimeter/submillimeter array in disks are caused by embedded protoplanets. | nine localized deviations from keplerian rotation in the dsharp circumstellar disks: kinematic evidence for protoplanets carving the gaps |
common-envelope (ce) evolution in massive binary systems is thought to be one of the most promising channels for the formation of compact binary mergers. in the case of merging binary black holes (bbhs), the essential ce phase takes place at a stage when the first bh is already formed and the companion star expands as a supergiant. we aim to decipher the kinds of bh binaries with supergiant companions that could potentially evolve through and survive a ce phase. to this end, we compute envelope binding energies from detailed massive stellar models at different evolutionary stages and metallicities. we make multiple physically extreme choices of assumptions that favor easier ce ejection as well as account for recent advancements in mass-transfer stability criteria. we find that even with the most optimistic assumptions, a successful ce ejection in bh binaries is only possible if the donor is a massive convective-envelope giant, namely a red supergiant (rsg). the same is true for neutron-star binaries with massive companions. in other words, pre-ce progenitors of bbh mergers are bh binaries with rsg companions. we find that because of its influence on the radial expansion of massive giants, metallicity has an indirect but a very strong effect on the chemical profile, density structure, and the binding energies of rsg envelopes. our results suggest that merger rates from population-synthesis models could be severely overestimated, especially at low metallicity. additionally, the lack of observed rsgs with luminosities above log(l/l⊙) ≈ 5.6 - 5.8, corresponding to stars with m ≳ 40 m⊙, puts into question the viability of the ce channel for the formation of the most massive bbh mergers. either such rsgs elude detection due to very short lifetimes, or they do not exist and the ce channel can only produce bbh systems with total mass ≲50 m⊙. finally, we discuss an alternative ce scenario in which a partial envelope ejection is followed by a phase of possibly long and stable mass transfer. | it has to be cool: supergiant progenitors of binary black hole mergers from common-envelope evolution |
when and how planets form in protoplanetary disks is still a topic of discussion. exoplanet detection surveys and protoplanetary disk surveys are now providing results that are leading to new insights. we collect the masses of confirmed exoplanets and compare their dependence on stellar mass with the same dependence for protoplanetary disk masses measured in ∼1-3 myr old star-forming regions. we recalculated the disk masses using the new estimates of their distances derived from gaia dr2 parallaxes. we note that single and multiple exoplanetary systems form two different populations, probably pointing to a different formation mechanism for massive giant planets around very low-mass stars. while expecting that the mass in exoplanetary systems is much lower than the measured disk masses, we instead find that exoplanetary systems masses are comparable or higher than the most massive disks. this same result is found by converting the measured planet masses into heavy element content (core masses for the giant planets and full masses for the super-earth systems) and by comparing this value with the disk dust masses. unless disk dust masses are heavily underestimated, this is a big conundrum. an extremely efficient recycling of dust particles in the disk cannot solve this conundrum. this implies that either the cores of planets have formed very rapidly (<0.1-1 myr) and a large amount of gas is expelled on the same timescales from the disk, or that disks are continuously replenished by fresh planet-forming material from the environment. these hypotheses can be tested by measuring disk masses in even younger targets and by better understanding if and how the disks are replenished by their surroundings. | why do protoplanetary disks appear not massive enough to form the known exoplanet population? |
we use a particle tracking analysis to study the origins of the circumgalactic medium (cgm), separating it into (1) accretion from the intergalactic medium (igm), (2) wind from the central galaxy, and (3) gas ejected from other galaxies. our sample consists of 21 fire-2 simulations, spanning the halo mass range mh ∼ 1010-1012 m⊙, and we focus on z = 0.25 and z = 2. owing to strong stellar feedback, only ∼l⋆ haloes retain a baryon mass ≳ 50 per cent of their cosmic budget. metals are more efficiently retained by haloes, with a retention fraction ≳ 50 per cent. across all masses and redshifts analysed ≳ 60 per cent of the cgm mass originates as igm accretion (some of which is associated with infalling haloes). overall, the second most important contribution is wind from the central galaxy, though gas ejected or stripped from satellites can contribute a comparable mass in ∼l⋆ haloes. gas can persist in the cgm for billions of years, resulting in well mixed-halo gas. sightlines through the cgm are therefore likely to intersect gas of multiple origins. for low-redshift ∼l⋆ haloes, cool gas (t < 104.7 k) is distributed on average preferentially along the galaxy plane, however with strong halo-to-halo variability. the metallicity of igm accretion is systematically lower than the metallicity of winds (typically by ≳1 dex), although cgm and igm metallicities depend significantly on the treatment of subgrid metal diffusion. our results highlight the multiple physical mechanisms that contribute to the cgm and will inform observational efforts to develop a cohesive picture. | the origins of the circumgalactic medium in the fire simulations |
observations of evolution in the dust-to-metal ratio allow us to constrain the dominant dust processing mechanisms. in this work, we present a study of the dust-to-metal and dust-to-gas ratios in a sub-sample of ~500 dustpedia galaxies. using literature and muse emission line fluxes, we derived gas-phase metallicities (oxygen abundances) for over 10 000 individual regions and determine characteristic metallicities for each galaxy. we study how the relative dust, gas, and metal contents of galaxies evolve by using metallicity and gas fraction as proxies for evolutionary state. the global oxygen abundance and nitrogen-to-oxygen ratio are found to increase monotonically as galaxies evolve. additionally, unevolved galaxies (gas fraction >60%, metallicity 12 + log(o/h) < 8.2) have dust-to-metal ratios that are about a factor of 2.1 lower (a factor of six lower for galaxies with gas fraction >80%) than the typical dust-to-metal ratio (md/mz ~ 0.214) for more evolved sources. however, for high gas fractions, the scatter is larger due to larger observational uncertainties as well as a potential dependence of the dust grain growth timescale and supernova dust yield on local conditions and star formation histories. we find chemical evolution models with a strong contribution from dust grain growth describe these observations reasonably well. the dust-to-metal ratio is also found to be lower for low stellar masses and high specific star formation rates (with the exception of some sources undergoing a starburst). finally, the metallicity gradient correlates weakly with the hi-to-stellar mass ratio, the effective radius and the dust-to-stellar mass ratio, but not with stellar mass. dustpedia is a project funded by the eu under the heading "exploitation of space science and exploration data". it has the primary goal of exploiting existing data in the herschel space observatory and planck telescope databases. additional tables are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/623/a5 | a systematic metallicity study of dustpedia galaxies reveals evolution in the dust-to-metal ratios |
we have presented a new anisotropic solution of einstein's field equations for compact-star models. einstein's field equations are solved by using the class-one condition (s.n. pandey, s.p. sharma, gen. relativ. gravit. 14, 113 (1982)). we constructed the expression for the anisotropy factor ( δ by using the pressure anisotropy condition and thereafter we obtained the physical parameters like energy density, radial and transverse pressure. these models parameters are well-behaved inside the star and satisfy all the required physical conditions. also we observed the very interesting result that all physical parameters depend upon the anisotropy factor ( δ. the mass and radius of the present compact-star models are quite compatible with the observational astrophysical compact stellar objects like her x-1, rxj 1856-37, sax j1808.4-3658(ss1), sax j1808.4-3658(ss2). | a new exact anisotropic solution of embedding class one |
in this work, we attempt to find an anisotropic solution for a compact star generated by gravitational decoupling in f(q)-gravity theory having a null complexity factor. to do this, we initially derive the complexity factor condition in f(q) gravity theory using the definition given by herrera (phys rev d 97:044010, 2018) and then derived a bridge equation between gravitational potentials by assuming complexity factor to be zero (contreras and stuchlik in eur phys j c 82:706, 2022). next, we obtain two systems of equations using the complete geometric deformation (cgd) approach. the first system of equations is assumed to be an isotropic system in f(q)-gravity whose isotropic condition is similar to gr while the second system is dependent on deformation functions. the solution of the first system is obtained by buchdahl's spacetime geometry while the governing equations for the second system are solved through the mimic constraint approach along with vanishing complexity condition. the novelty of our work is to generalize the perfect fluid solution into an anisotropic domain in f(q)-gravity theory with zero complexity for the first time. we present the solution's analysis to test its physical viability. we exhibit that the existence of pressure anisotropy due to gravitational within the self-gravitating bounded object plays a vital role to stabilize the f(q) gravity system. in addition, we show that the constant involved in the solution controls the direction of energy flow between the perfect fluid and generic fluid matter distributions. | complexity-free solution generated by gravitational decoupling for anisotropic self-gravitating star in symmetric teleparallel f(q)-gravity theory |
we report the detection of a transiting planet around π men (hd 39091), using data from the transiting exoplanet survey satellite (tess). the solar-type host star is unusually bright (v = 5.7) and was already known to host a jovian planet on a highly eccentric, 5.7 yr orbit. the newly discovered planet has a size of 2.04 ± 0.05 r ⊕ and an orbital period of 6.27 days. radial-velocity data from the high-accuracy radial-velocity planet searcher and anglo-australian telescope/university college london echelle spectrograph archives also displays a 6.27 day periodicity, confirming the existence of the planet and leading to a mass determination of 4.82 ± 0.85 m ⊕. the star’s proximity and brightness will facilitate further investigations, such as atmospheric spectroscopy, asteroseismology, the rossiter-mclaughlin effect, astrometry, and direct imaging. | tess discovery of a transiting super-earth in the pi mensae system |
the neutron star (ns) merger gw170817 was followed over several days by optical-wavelength (“blue”) kilonova (kn) emission likely powered by the radioactive decay of light r-process nuclei synthesized by ejecta with a low neutron abundance (electron fraction ye≈ 0.25-0.35). while the composition and high velocities of the blue kn ejecta are consistent with shock-heated dynamical material, the large quantity is in tension with the results of numerical simulations. we propose an alternative ejecta source: the neutrino-heated, magnetically accelerated wind from the strongly magnetized hypermassive ns (hmns) remnant. a rapidly spinning hmns with an ordered surface magnetic field of strength b ≈ (1-3) × 1014 g and lifetime t rem ∼ 0.1-1 s can simultaneously explain the velocity, total mass, and electron fraction of the blue kn ejecta. the inferred hmns lifetime is close to its alfvén crossing time, suggesting that global magnetic torques could be responsible for bringing the hmns into solid-body rotation and instigating its gravitational collapse. different origins for the kn ejecta may be distinguished by their predictions for the emission in the first hours after the merger, when the luminosity is enhanced by heating from internal shocks; the latter are likely generic to any temporally extended ejecta source (e.g., magnetar or accretion disk wind) and are not unique to the emergence of a relativistic jet. the same shocks could mix and homogenize the composition to a low but nonzero lanthanide mass fraction, {x}la}≈ {10}-3, as advocated by some authors, but only if the mixing occurs after neutrons are consumed in the r-process on a timescale ≳1 s. | a magnetar origin for the kilonova ejecta in gw170817 |
the discovery by advanced ligo/virgo of gravitational waves from the binary neutron star (ns) merger gw170817, and subsequently by astronomers of transient counterparts across the electromagnetic (em) spectrum, has initiated the era of multi-messenger astronomy. given the slew of papers appearing on this event, i thought it useful to summarize the em discoveries in the context of theoretical models and present my views on the major take-away lessons from this watershed event. the weak grb discovered in close time coincidence with gw170817, and potential evidence for a more powerful off-axis relativistic jet (initially beamed away from our line of sight) from the delayed rise of a non-thermal x-ray and radio orphan afterglow, provides the most compelling evidence yet that cosmological short grbs originate from binary ns mergers. the luminosity and colors of the early optical emission discovered within a day of the merger agrees strikingly well with original predictions (metzger et al. 2010) for "kilonova" emission powered by the radioactive decay of r-process nuclei, the ns merger origin of which was initially proposed by lattimer & schramm 1974. the transition of the spectral energy distribution to nir wavelengths on timescales of days matches predictions by barnes & kasen 2013 and tanaka & hotokezaka 2013 if a portion of the ejecta contains heavy r-process nuclei with higher opacities. the "blue" and "red" ejecta components may possess distinct origins (e.g. dynamical ejecta versus accretion disk outflows), with key implications for the merger physics and the properties of neutron stars. i outline the diversity in the em emission expected from additional mergers-observed with different binary masses and viewing angles-discovered once ligo/virgo reach design sensitivity and ns mergers are discovered as frequently as once per week. | welcome to the multi-messenger era! lessons from a neutron star merger and the landscape ahead |
neutron star interiors provide the opportunity to probe properties of cold dense matter in the qcd phase diagram. utilizing models of dense matter in accord with nuclear systematics at nuclear densities, we investigate the compatibility of deconfined quark cores with current observational constraints on the maximum mass and tidal deformability of neutron stars. we explore various methods of implementing the hadron-to-quark phase transition, specifically, first-order transitions with sharp (maxwell construction) and soft (gibbs construction) interfaces, and smooth crossover transitions. we find that within the models we apply, hadronic matter has to be stiff for a first-order phase transition and soft for a crossover transition. in both scenarios and for the equations of state we employed, quarks appear at the center of premerger neutron stars in the mass range ≈1.0 - 1.6 m⊙ , with a squared speed of sound cqm2≳0.4 characteristic of strong repulsive interactions required to support the recently discovered neutron star masses ≥2 m⊙ . we also identify equations of state and phase transition scenarios that are consistent with the bounds placed on tidal deformations of neutron stars in the recent binary merger event gw170817. we emphasize that distinguishing hybrid stars with quark cores from normal hadronic stars is very difficult from the knowledge of masses and radii alone, unless drastic sharp transitions induce distinctive disconnected hybrid branches in the mass-radius relation. | treating quarks within neutron stars |
we study the impact of large-scale perturbations from convective shell burning on the core-collapse supernova explosion mechanism using 3d multigroup neutrino hydrodynamics simulations of an 18m⊙ progenitor. seed asphericities in the o shell, obtained from a recent 3d model of o shell burning, help trigger a neutrino-driven explosion 330 ms after bounce whereas the shock is not revived in a model based on a spherically symmetric progenitor for at least another 300 ms. we tentatively infer a reduction of the critical luminosity for shock revival by ∼ 20 {per cent} due to pre-collapse perturbations. this indicates that convective seed perturbations play an important role in the explosion mechanism in some progenitors. we follow the evolution of the 18m⊙ model into the explosion phase for more than 2 s and find that the cycle of accretion and mass ejection is still ongoing at this stage. with a preliminary value of 7.7 × 1050 erg for the diagnostic explosion energy, a baryonic neutron star mass of 1.85m⊙, a neutron star kick of ∼ 600 km s^{-1} and a neutron star spin period of ∼ 20 ms at the end of the simulation, the explosion and remnant properties are slightly atypical, but still lie comfortably within the observed distribution. although more refined simulations and a larger survey of progenitors are still called for, this suggests that a solution to the problem of shock revival and explosion energies in the ballpark of observations is within reach for neutrino-driven explosions in 3d. | supernova simulations from a 3d progenitor model - impact of perturbations and evolution of explosion properties |
we present a detailed study of the rest-optical (3600-7000 å) nebular spectra of ∼380 star-forming galaxies at z≃ 2{--}3, obtained with keck/multi-object spectrometer for infrared exploration (mosfire) as part of the keck baryonic structure survey (kbss). the kbss-mosfire sample is representative of star-forming galaxies at these redshifts, with stellar masses {m}* ={10}9{--}{10}11.5 {m}⊙and star formation rates sfr = 3-1000 {m}⊙yr-1. we focus on robust measurements of many strong diagnostic emission lines for individual galaxies: [o ii]λλ3727, 3729, [ne iii]λ3869, hβ, [o iii]λ λ 4960, 5008, [n ii]λλ 6549, 6585, hα, and [s ii]λλ6718, 6732. comparisons with observations of typical local galaxies from the sloan digital sky survey and between subsamples of kbss-mosfire show that high-redshift galaxies exhibit a number of significant differences in addition to the well-known offset in log([o iii]λ 5008/hβ) and log([n ii]λ 6585/hα). we argue that the primary difference between h ii regions in z∼ 2.3 galaxies and those at z∼ 0 is an enhancement in the degree of nebular excitation, as measured by [o iii]/hβ and {{r}}23\equiv {log}[([o iii]λ λ 4960,5008+[o ii]λ λ 3727,3729)/hβ]. at the same time, kbss-mosfire galaxies are ∼10 times more massive than z∼ 0 galaxies with similar ionizing spectra and have higher n/o (likely accompanied by higher o/h) at fixed excitation. these results indicate the presence of harder ionizing radiation fields at fixed n/o and o/h relative to typical z∼ 0 galaxies, consistent with fe-poor stellar population models that include massive binaries, and highlight a population of massive, high-specific star formation rate galaxies at high redshift with systematically different star formation histories than galaxies of similar stellar mass today. the data presented in this paper were obtained at the w.m. keck observatory, which is operated as a scientific partnership among the california institute of technology, the university of california, and the national aeronautics and space administration. the observatory was made possible by the generous financial support of the w.m. keck foundation. | nebular emission line ratios in z ≃ 2-3 star-forming galaxies with kbss-mosfire: exploring the impact of ionization, excitation, and nitrogen-to-oxygen ratio |
the repeating fast radio burst source frb 121102 has been shown to have an exceptionally high and variable faraday rotation measure (rm), which must be imparted within its host galaxy, likely by or within its local environment. in the redshifted (z = 0.193) source reference frame, the rm decreased from 1.46 × 105 rad m-2 to 1.33 × 105 rad m-2 between 2017 january and august, showing day-timescale variations of ∼200 rad m-2. here we present 16 frb 121102 rms from burst detections with the arecibo 305 m radio telescope, the effelsberg 100 m, and the karl g. jansky very large array, providing a record of frb 121102's rm over a 2.5 yr time span. our observations show a decreasing trend in rm, although the trend is not linear, dropping by an average of 15% year-1 and is ∼ 9.7 × 104 rad m-2 at the most recent epoch of 2019 august. erratic, short-term rm variations of ∼103 rad m-2 week-1 were also observed between mjds 58215-58247. a decades-old neutron star embedded within a still-compact supernova remnant or a neutron star near a massive black hole and its accretion torus have been proposed to explain the high rms. we compare the observed rms to theoretical models describing the rm evolution for frbs originating within a supernova remnant. frb 121102's age is unknown, and we find that the models agree for source ages of ∼6-17 yr at the time of the first available rm measurements in 2017. we also draw comparisons to the decreasing rm of the galactic center magnetar, psr j1745-2900. | rotation measure evolution of the repeating fast radio burst source frb 121102 |
we use the new modular open source fitter for transients to model 38 hydrogen-poor superluminous supernovae (slsne). we fit their multicolor light curves with a magnetar spin-down model and present posterior distributions of magnetar and ejecta parameters. the color evolution can be fit with a simple absorbed blackbody. the medians (1σ ranges) for key parameters are spin period 2.4 ms (1.2-4 ms), magnetic field 0.8× {10}14 g (0.2{--}1.8× {10}14 g), ejecta mass 4.8 {m}⊙(2.2-12.9 {m}⊙ ), and kinetic energy 3.9× {10}51 erg (1.9{--}9.8× {10}51 erg). this significantly narrows the parameter space compared to our uninformed priors, showing that although the magnetar model is flexible, the parameter space relevant to slsne is well constrained by existing data. the requirement that the instantaneous engine power is ∼1044 erg at the light-curve peak necessitates either large rotational energy (p < 2 ms), or more commonly that the spin-down and diffusion timescales be well matched. we find no evidence for separate populations of fast- and slow-declining slsne, which instead form a continuum in light-curve widths and inferred parameters. variations in the spectra are explained through differences in spin-down power and photospheric radii at maximum light. we find no significant correlations between model parameters and host galaxy properties. comparing our posteriors to stellar evolution models, we show that slsne require rapidly rotating (fastest 10%) massive stars (≳ 20 {m}⊙ ), which is consistent with their observed rate. high mass, low metallicity, and likely binary interaction all serve to maintain rapid rotation essential for magnetar formation. by reproducing the full set of light curves, our posteriors can inform photometric searches for slsne in future surveys. | the magnetar model for type i superluminous supernovae. i. bayesian analysis of the full multicolor light-curve sample with mosfit |
long-duration gamma-ray bursts (grbs) are powerful cosmic explosions, signaling the death of massive stars. among them, grb 221009a is by far the brightest burst ever observed. because of its enormous energy ( e iso ≈ 10 55 erg) and proximity ( z ≈ 0.15), grb 221009a is an exceptionally rare event that pushes the limits of our theories. we present multiwavelength observations covering the first 3 months of its afterglow evolution. the x-ray brightness decays as a power law with slope ≈ t −1.66 , which is not consistent with standard predictions for jetted emission. we attribute this behavior to a shallow energy profile of the relativistic jet. a similar trend is observed in other energetic grbs, suggesting that the most extreme explosions may be powered by structured jets launched by a common central engine. the afterglow of grb 221009a implies a shallow structured jet is produced in the most powerful stellar explosions. | a structured jet explains the extreme grb 221009a |
we present an early analysis on the search for high-redshift galaxies using the deepest public jwst imaging to date, the ngdeep field. these data consist of six-band nircam imaging on the hubble ultra deep field parallel 2 (hudf-par2), covering a total area of 6.3 arcmin2. based on our initial reduction of the first half of this survey, we reach 5σ depths up to mag = 29.5-29.9 between 1 and 5 μm. such depths present an unprecedented opportunity to begin exploring the very early universe with jwst. as such, we find high-redshift galaxies by examining the spectral energy distribution of all f444w detections and present 16 new z > 8.5 galaxies identified using two different photometric redshift codes: lephare and eazy combined with other significance criteria. the highest-redshift object in our sample is at $z={15.6}_{-0.3}^{+0.4}$ , which has a blue $\beta =-{3.02}_{-0.46}^{+0.42}$ and a very low inferred stellar mass of m * = 107.4 m ⊙. we also discover a series of faint, low-mass dwarf galaxies with m * < 108.5 m ⊙ at z ~ 9 that have blue colors, flat surface brightness profiles, and small sizes <1 kpc. comparing to previous work in the hudf-par2, we find 21 6 < z < 9 candidates including two z = 8 major mergers. one of these merger candidates has an additional two z = 8 sources within 30″, indicating that it may form part of an overdensity. we also compare our results to theory, finding no significant disagreement with a few cold-dark-matter-based models. the discovery of these objects demonstrates the critical need for deeper, or similar depth but wider-area, jwst surveys to explore the early universe. | a large population of faint 8 < z < 16 galaxies found in the first jwst nircam observations of the ngdeep survey |
we present n-body simulations of a sagittarius (sgr)-like dwarf spheroidal galaxy that follows its orbit about the milky way (mw) since its first crossing of the galaxy's virial radius to the present day. as sgr orbits around the mw, it excites vertical oscillations, corrugating and flaring the galactic stellar disc. these responses can be understood by a two-phase picture in which the interaction is first dominated by torques from the wake excited by sgr in the mw dark halo before transitioning to tides from sgr's direct impact on the disc at late times. we show for the first time that a massive sgr model simultaneously reproduces the locations and motions of arclike overdensities, such as the monoceros ring and the triangulum andromeda stellar clouds, that have been observed at the extremities of the disc, while also satisfying the solar-neighbourhood constraints on the vertical structure and streaming motions of the disc. in additional simulations, we include the large magellanic cloud (lmc) self-consistently with sgr. the lmc introduces coupling through constructive and destructive interference, but no new corrugations. in our models, the excitation of the current structure of the outer disc can be traced to interactions as far back as 6-7gyr ago (corresponding to z ≤ 1). given the apparently quiescent accretion history of the mw over this time-scale, this places sgr as the main culprit behind the vertical oscillations of the disc and the last major accretion event for the galaxy with the capacity to modulate its chemodynamical structure. | the influence of sagittarius and the large magellanic cloud on the stellar disc of the milky way galaxy |
the monte carlo evaluation of path integrals is one of a few general purpose methods to approach strongly coupled systems. it is used in all branches of physics, from qcd/nuclear physics to the correlated electron systems. however, many systems of great importance (dense matter inside neutron stars, the repulsive hubbard model away from half-filling, dynamical and non-equilibrium observables) are not amenable to the monte carlo method as it currently stands due to the so-called "sign-problem". we review a new set of ideas recently developed to tackle the sign problem based on the complexification of field space and the picard-lefshetz theory accompanying it. the mathematical ideas underpinning this approach, as well as the algorithms so far developed, are described together with non-trivial examples where the method has already been proved successful. directions of future work, including the burgeoning use of machine learning techniques, are delineated. | complex paths around the sign problem |
we carried out a bayesian homogeneous determination of the orbital parameters of 231 transiting giant planets (tgps) that are alone or have distant companions; we employed differential evolution markov chain monte carlo methods to analyse radial-velocity (rv) data from the literature and 782 new high-accuracy rvs obtained with the harps-n spectrograph for 45 systems over 3 years. our work yields the largest sample of systems with a transiting giant exoplanet and coherently determined orbital, planetary, and stellar parameters. we found that the orbital parameters of tgps in non-compact planetary systems are clearly shaped by tides raised by their host stars. indeed, the most eccentric planets have relatively large orbital separations and/or high mass ratios, as expected from the equilibrium tide theory. this feature would be the outcome of planetary migration from highly eccentric orbits excited by planet-planet scattering, kozai-lidov perturbations, or secular chaos. the distribution of α = a/ar, where a and ar are the semi-major axis and the roche limit, for well-determined circular orbits peaks at 2.5; this agrees with expectations from the high-eccentricity migration (hem), although it might not be limited to this migration scenario. the few planets of our sample with circular orbits and α> 5 values may have migrated through disc-planet interactions instead of hem. by comparing circularisation times with stellar ages, we found that hot jupiters with a< 0.05 au have modified tidal quality factors 105 ≲ q'p ≲ 109, and that stellar q's ≳ 106 - 107 are required to explain the presence of eccentric planets at the same orbital distance. as aby-product of our analysis, we detected a non-zero eccentricity e = 0.104-0.018+0.021 for hat-p-29; we determined that five planets that were previously regarded to be eccentric or to have hints of non-zero eccentricity, namely corot-2b, corot-23b, tres-3b, hat-p-23b, and wasp-54b, have circular orbits or undetermined eccentricities; we unveiled curvatures caused by distant companions in the rv time series of hat-p-2, hat-p-22, and hat-p-29; we significantly improved the orbital parameters of the long-period planet hat-p-17c; and we revised the planetary parameters of corot-1b, which turned out to be considerably more inflated than previously found. full tables 1, 2, 5-9 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/602/a107 | the gaps programme with harps-n at tng . xiv. investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets |
we report the detection of extended lyα emission around individual star-forming galaxies at redshifts z = 3-6 in an ultradeep exposure of the hubble deep field south obtained with muse on the eso-vlt. the data reach a limiting surface brightness (1σ) of ~1 × 10-19 erg s-1 cm-2 arcsec-2 in azimuthally averaged radial profiles, an order of magnitude improvement over previous narrowband imaging. our sample consists of 26 spectroscopically confirmed lyα-emitting, but mostly continuum-faint (mab ≳ 27) galaxies. in most objects the lyα emission is considerably more extended than the uv continuum light. while five of the faintest galaxies in the sample show no significantly detected lyα haloes, the derived upper limits suggest that this is due to insufficient s/n. lyα haloes therefore appear to be ubiquitous even for low-mass (~ 108-109 m⊙) star-forming galaxies at z > 3. we decompose the lyα emission of each object into a compact component tracing the uv continuum and an extended halo component, and infer sizes and luminosities of the haloes. the extended lyα emission approximately follows an exponential surface brightness distribution with a scale length of a few kpc. while these haloes are thus quite modest in terms of their absolute sizes, they are larger by a factor of 5-15 than the corresponding rest-frame uv continuum sources as seen by hst. they are also much more extended, by a factor ~5, than lyα haloes around low-redshift star-forming galaxies. between ~40% and ≳90% of the observed lyα flux comes from the extended halo component, with no obvious correlation of this fraction with either the absolute or the relative size of the lyα halo. our observations provide direct insights into the spatial distribution of at least partly neutral gas residing in the circumgalactic medium of low to intermediate mass galaxies at z > 3. | extended lyman α haloes around individual high-redshift galaxies revealed by muse |
this work aims to investigate the behaviour of compact stars in the background of theory of gravity. for current work, we consider the krori-barua metric potential i.e., and , where, and c are constants. we use matching conditions of spherically symmetric space-time with schwarzschild solution as an exterior geometry and examine the physical behaviour of stellar structure by assuming the exponential type gravity model. in the present analysis, we discuss the graphical behaviour of energy density, radial pressure, tangential pressure, equation of state parameters, anisotropy and stability analysis respectively. furthermore, an equilibrium condition can be visualized through the modified tolman-oppenheimer-volkov equation. some extra features of compact stars i.e. mass-radius function, compactness factor and surface redshift have also been investigated. conclusively, all the results in current study validate the existence of compact stars under exponential gravity model.this work aims to investigate the behaviour of compact stars in the background of f (r, t) theory of gravity. for current work, the authors consider the krori-barua metric potential i.e., ν(r) = br2 + c and λ(r) = ar2, where, a, b and c are constants. they use matching conditions of spherically symmetric space-time with schwarzschild solution as an exterior geometry and examine the physical behaviour of stellar structure by assuming the exponential type f (r, t) gravity model. the investigation presented here contains both a discussion of the graphical behaviour of energy density, the radial and tangential pressure, the equation of state parameters, anisotropy and and a stability analysis respectively. furthermore, an equilibrium condition can be visualized through the modified tolman-oppenheimer-volkov equation. some extra features of compact stars i.e. mass-radius function, compactness factor and surface redshift have also been investigated. conclusively, all the results in current study validate the existence of compact stars under exponential f (r, t) gravity model. | relativistic krori-barua compact stars in f(r,t)f(r,t) gravity |
we review the physics of hyperons and δ-resonances in dense matter in compact stars. the covariant density functional approach to the equation of state and composition of dense nuclear matter in the mean-field hartree and hartree-fock approximation is presented, with regimes covering cold β-equilibrated matter, hot and dense matter with and without neutrinos relevant for the description of supernovas and binary neutron star mergers, as well as dilute expanding nuclear matter in collision experiments. we discuss the static properties of compact stars with hyperons and δ-resonances in light of constraints placed in recent years by the multimessenger astrophysics of compact stars on the compact stars' masses, radii, and tidal deformabilities. the effects of kaon condensation and strong magnetic fields on the composition of hypernuclear stars are also discussed. the properties of rapidly rotating compact hypernuclear stars are discussed and confronted with the observations of 2.5-2.8 solar mass compact objects in gravitational wave events. we further discuss the cooling of hypernuclear stars, the neutrino emission reactions, hyperonic pairing, and the mass hierarchy in the cooling curves that arises due to the onset of hyperons. the effects of hyperons and δ-resonances on the equation of state of hot nuclear matter in the dense regime, relevant for the transient astrophysical event and in the dilute regime relevant to the collider physics is discussed. the review closes with a discussion of universal relations among the integral parameters of hot and cold hypernuclear stars and their implications for the analysis of binary neutron star merger events. | heavy baryons in compact stars |
advanced ligo and advanced virgo are detecting a large number of binary stellar origin black hole (bh) mergers. a promising channel for accelerated bh merger lies in active galactic nucleus (agn) discs of gas around supermasssive bhs. here, we investigate the relative number of compact object (co) mergers in agn disc models, including bh, neutron stars (ns), and white dwarfs, via monte carlo simulations. we find the number of all merger types in the bulk disc grows ∝ t1/3 which is driven by the hill sphere of the more massive merger component. median mass ratios of ns-bh mergers in agn discs are $\tilde{q}=0.07\pm 0.06(0.14\pm 0.07)$ for mass functions (mf) m-1(- 2). if a fraction fagn of the observed rate of bh-bh mergers (rbh-bh) come from agn, the rate of ns-bh (ns-ns) mergers in the agn channel is ${r}_{\mathrm{ bh}\!-\!\mathrm{ ns}} \sim f_{\mathrm{ agn}}[10,300]\, \rm {gpc}^{-3}\, \rm {yr}^{-1},({\mathit{ r}}_{ns\!-\!ns} \le \mathit{ f}_{agn}400\, \rm {gpc}^{-3}\, \rm {yr}^{-1}$). given the ratio of ns-ns/bh-bh ligo search volumes, from preliminary o3 results the agn channel is not the dominant contribution to observed ns-ns mergers. the number of lower mass gap events expected is a strong function of the nuclear mf and mass segregation efficiency. co merger ratios derived from ligo can restrict models of mf, mass segregation, and populations embedded in agn discs. the expected number of electromagnetic (em) counterparts to ns-bh mergers in agn discs at z < 1 is $\sim [30,900]\, {\rm {yr}}^{-1}(f_{\mathrm{ agn}}/0.1)$. em searches for flaring events in large agn surveys will complement ligo constraints on agn models and the embedded populations that must live in them. | black hole, neutron star, and white dwarf merger rates in agn discs |
gravitational-wave detections have revealed a previously unknown population of stellar mass black holes with masses above 20 m ⊙. these observations provide a new way to test models of stellar evolution for massive stars. by considering the astrophysical processes likely to determine the shape of the binary black hole mass spectrum, we construct a parameterized model to capture key spectral features that relate gravitational-wave data to theoretical stellar astrophysics. in particular, we model the signature of pulsational pair-instability supernovae, which are expected to cause all stars with initial mass 100 m ⊙ ≲ m ≲ 150 m ⊙ to form ∼40 m ⊙ black holes. this would cause a cutoff in the black hole mass spectrum along with an excess of black holes near 40 m ⊙. we carry out a simulated data study to illustrate some of the stellar physics that can be inferred using gravitational-wave measurements of binary black holes and demonstrate several such inferences that might be made in the near future. first, we measure the minimum and maximum stellar black hole mass. second, we infer the presence of a peak due to pair-instability supernovae. third, we measure the distribution of black hole mass ratios. finally, we show how inadequate models of the black hole mass spectrum lead to biased estimates of the merger rate and the amplitude of the stochastic gravitational-wave background. | measuring the binary black hole mass spectrum with an astrophysically motivated parameterization |
the kepler mission has discovered thousands of planets with radii <4 {r}\oplus , paving the way for the first statistical studies of the dynamics, formation, and evolution of these sub-neptunes and super-earths. planetary masses are an important physical property for these studies, and yet the vast majority of kepler planet candidates do not have theirs measured. a key concern is therefore how to map the measured radii to mass estimates in this earth-to-neptune size range where there are no solar system analogs. previous works have derived deterministic, one-to-one relationships between radius and mass. however, if these planets span a range of compositions as expected, then an intrinsic scatter about this relationship must exist in the population. here we present the first probabilistic mass-radius relationship (m-r relation) evaluated within a bayesian framework, which both quantifies this intrinsic dispersion and the uncertainties on the m-r relation parameters. we analyze how the results depend on the radius range of the sample, and on how the masses were measured. assuming that the m-r relation can be described as a power law with a dispersion that is constant and normally distributed, we find that m/{m}\oplus =2.7{(r/{r}\oplus )}1.3, a scatter in mass of 1.9{m}\oplus , and a mass constraint to physically plausible densities, is the “best-fit” probabilistic m-r relation for the sample of rv-measured transiting sub-neptunes (r pl < 4 {r}\oplus ). more broadly, this work provides a framework for further analyses of the m-r relation and its probable dependencies on period and stellar properties. | probabilistic mass-radius relationship for sub-neptune-sized planets |
the mass spectrum of stellar mass black holes (bhs) is highly uncertain. dynamical mass measurements are available only for few (∼10) bhs in x-ray binaries, while theoretical models strongly depend on the hydrodynamics of supernova (sn) explosions and on the evolution of massive stars. in this paper, we present and discuss the mass spectrum of compact remnants that we obtained with sevn, a new public population-synthesis code, which couples the parsec stellar evolution tracks with up-to-date recipes for sn explosion (depending on the carbon-oxygen mass of the progenitor, on the compactness of the stellar core at pre-sn stage and on a recent two-parameter criterion based on the dimensionless entropy per nucleon at pre-sn stage). sevn can be used both as a stand-alone code and in combination with direct-summation n-body codes (starlab, higpus). the parsec stellar evolution tracks currently implemented in sevn predict significantly larger values of the carbon-oxygen core mass with respect to previous models. for most of the sn recipes we adopt, this implies substantially larger bh masses at low metallicity (≤2 × 10-3), than other population synthesis codes. the maximum bh mass found with sevn is ∼25, 60 and 130 m⊙ at metallicity z = 2 × 10-2, 2 × 10-3 and 2 × 10-4, respectively. mass loss by stellar winds plays a major role in determining the mass of bhs for very massive stars (≥90 m⊙), while the remnant mass spectrum depends mostly on the adopted sn recipe for lower progenitor masses. we discuss the implications of our results for the transition between neutron star and bh mass, and for the expected number of massive bhs (with mass >25 m⊙) as a function of metallicity. | the mass spectrum of compact remnants from the parsec stellar evolution tracks |
we present a novel relativistic density-functional approach to modeling quark matter with a mechanism to mimic confinement. the quasiparticle treatment of quarks provides their suppression due to a large quark self energy already at the mean-field level. we demonstrate that our approach is equivalent to a chiral quark model with medium-dependent couplings. the dynamical restoration of the chiral symmetry is ensured by construction of the density functional. supplemented with the vector repulsion and diquark pairing, the model is applied to construct a hybrid quark-hadron equation of state of cold compact-star matter. we study the connection of such a hybrid equation of state with the stellar mass-radius relation and tidal deformability. the model results are compared to various observational constraints, including the nicer radius measurement of psr j 0740 +6620 and the tidal deformability constraint from gw170817. as a striking result, we present selected parametrizations for which the hybrid star sequence reaches masses in the range 2.5 - 2.67 m⊙ of the lighter object in the merger gw190814, which therefore might be interpreted as the heaviest neutron star with to date. | density functional approach to quark matter with confinement and color superconductivity |
based on various diagnostics and corrections established in the framework of several sunspot number workshops and described by clette et al. (space sci. rev.186, 35, 2014), we now assembled all separately derived corrections to produce a new standard version of the reference sunspot-number time series. we explain here the three main corrections and the criteria used to choose a final optimal version of each correction factor or function, given the available information and published analyses. we then discuss the differences between the new corrected series and the original sunspot number, including the disappearance of any significant rising secular trend in the solar-cycle amplitudes after this recalibration. we also introduce the new version management scheme now implemented at the world data center sunspot index and long-term solar observations (wdc-silso), which reflects a major conceptual transition: beyond the rescaled numbers, this first revision of the sunspot number also transforms the former static data archive into a living observational series open to future improvements. | the new sunspot number: assembling all corrections |
the organic-inorganic hybrid lead halide perovskites have emerged as a series of star materials for solar cells, lasers and detectors. however, the issues raised by the toxic lead element and marginal stability due to the volatile organic components have severely limited their potential applications. in this work, we develop a nucleation-controlled solution method to grow large size high-quality cs3bi2i9 perovskite single crystals (pscs). using the technique, we harvest some centimeter-sized single crystals and achieved high device performance. we find that x-ray detectors based on pscs exhibit high sensitivity of 1652.3 μc gyair-1 cm-2 and very low detectable dose rate of 130 ngyair s-1, both desired in medical diagnostics. in addition, its outstanding thermal stability inspires us to develop a high temperature x-ray detector with stable response at up to 100 °c. furthermore, pscs exhibit high x-ray imaging capability thanks to its negligible signal drifting and extremely high stability. | nucleation-controlled growth of superior lead-free perovskite cs3bi2i9 single-crystals for high-performance x-ray detection |
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