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By contrast. for the single phase calculation. all the gas in the inter-armi regions is likely to increase in temperature above LOO Ix. For the multi-phase simulation. the density of the T00Ix eas (inclusive of Ls) ison average L2.107 ecm and 710τὸ g ? for the inter-arm anc spiral armi regions respectively (Fig. | By contrast, for the single phase calculation, all the gas in the inter-arm regions is likely to increase in temperature above 100 K. For the multi-phase simulation, the density of the 100K gas (inclusive of $_2$ ) is on average $1-2 \times 10^{-23}$ g $^{-3}$ and $7 \times 10^{-23}$ g $^{-3}$ for the inter-arm and spiral arm regions respectively (Fig. |
5). | 5). |
?. [ind from nioclels of photoclissociaion regions (PDRs) that CO(1-0) emission is detected when the density is 10 I«nLO 7. | \citet{Allen2004} find from models of photodissociaion regions (PDRs) that CO(1-0) emission is detected when the density is 10 $^{-3}<n<10^5$ $^{-3}$. |
Whilst the spiral arn densities are high enough to be detected in CO. much of the inter-arni gas in our simulation lies below this regime and would be dillicult to detect. observationallv. | Whilst the spiral arm densities are high enough to be detected in CO, much of the inter-arm gas in our simulation lies below this regime and would be difficult to detect observationally. |
? also show that the CO to Il» conversion factor is roughly constant [or a LOO cm* cloud in a low UV field. providing the column density is 24.1075 (comparable with the column density threshold: used for our clump finding algorithms). | \citet{Kaufman1999} also show that the CO to $_2$ conversion factor is roughly constant for a 100 $^{-3}$ cloud in a low UV field, providing the column density is $\gtrsim 4 \times 10^{21}$ $^{-2}$ (comparable with the column density threshold used for our clump finding algorithms). |
Below these densities. or with a higher UV field. LH» is significantly underestimated from CO observations since CO is dissociated more reacilv than LH». | Below these densities, or with a higher UV field, $_2$ is significantly underestimated from CO observations since CO is dissociated more readily than$_2$ . |
Fig. | Fig. |
4 further indicates that the column density of the inter-arm molecular gas is typically between 510 g em7. | 4 further indicates that the column density of the inter-arm molecular gas is typically between $5\times10^{-4}-10^{-3}$ g $^{-2}$. |
This is an order of magnitude Less than the column densities of lls observed for LIISA clouds which are associated with CO emission (2).. | This is an order of magnitude less than the column densities of $_2$ observed for HISA clouds which are associated with CO emission \citep{Klaassen2005}. . |
Llowever ? also examine IIISA clouds where there is no CO emission. but infer. by means of radiative transfer techniques. column densities of II» for these clouds of around. 10.7 g em.7. | However \citet{Klaassen2005} also examine HISA clouds where there is no CO emission, but infer, by means of radiative transfer techniques, column densities of $_2$ for these clouds of around $10^{-3}$ g $^{-2}$. |
We postulate ju the hot component of the ISM confines clouds of cold —Llto sullicientdensities to maintain a low level of Hs. | We postulate that the hot component of the ISM confines clouds of cold HIto sufficientdensities to maintain a low level of $_2$ . |
The | The |
the IRAF package. which is based on y minimization with the Levenberg-Marquardt method. | the IRAF package, which is based on $\chi^2$ minimization with the Levenberg-Marquardt method. |
We used for different logg values (7.0. 7.5. 8.0. 8.5 and 9.0) with Τω às a free parameter. obtaining different y for each fit. | We used for different $\log g$ values (7.0, 7.5, 8.0, 8.5 and 9.0) with $T_{\rm eff}$ as a free parameter, obtaining different $\chi^2$ for each fit. |
In each case. the initial estimate for Tay obtained from the spectral energy distribution (photometry in the BV and JHK bands. 2MASS) Was used as a starting guess. | In each case, the initial estimate for $T_{\rm eff}$ obtained from the spectral energy distribution (photometry in the $BV$ and $JHK$ bands, 2MASS) was used as a starting guess. |
The uncertainties 1n the derived Tey Were estimated from the perturbations required to increase the value of the reduced y by one. | The uncertainties in the derived $T_{\rm eff}$ were estimated from the perturbations required to increase the value of the reduced $\chi^2$ by one. |
The determination of logg was performed in an analogous way but to calculate the errors we took into account the prescription of Bergeronetal.(1992). who derive them from the independent fits of the individual exposures for any given star (before the combination). | The determination of $\log g$ was performed in an analogous way but to calculate the errors we took into account the prescription of \cite{ber92}, who derive them from the independent fits of the individual exposures for any given star (before the combination). |
The results are given in Table 4.. | The results are given in Table \ref{tab:4}. |
In Fig. | In Fig. |
| we show the fits for some of the DA white dwarfs in our sample. | 1 we show the fits for some of the DA white dwarfs in our sample. |
Some of these white dwarfs had been the subject of previous analyses which allow us to perform a comparison with our results. | Some of these white dwarfs had been the subject of previous analyses which allow us to perform a comparison with our results. |
For instance. WD0913+442 was also studied by Bergeronetal. (1995).. who obtained atmospheric parameters compatible with the ones derived here. | For instance, $+$ 442 was also studied by \cite{ber95}, , who obtained atmospheric parameters compatible with the ones derived here. |
They also studied WDI3544340 and WD2253-081. but in these cases the effective temperatures obtained are compatible with ours while the surface gravities are not. although just outside the lo error bar. | They also studied $+$ 340 and $-$ 081, but in these cases the effective temperatures obtained are compatible with ours while the surface gravities are not, although just outside the $1\sigma$ error bar. |
We have obtained lower values of loge in both cases. which could be due to the different resolution of the spectra FHWM in their case). | We have obtained lower values of $\log g$ in both cases, which could be due to the different resolution of the spectra $\sim6$ FHWM in their case). |
This latter object. WD2253-081. is of particular interest since an accurate fit of its line profiles posed many problems to previous analyses because the lines seemed to be broader than the models predicted. | This latter object, $-$ 081, is of particular interest since an accurate fit of its line profiles posed many problems to previous analyses because the lines seemed to be broader than the models predicted. |
This led different authors to consider the possibility of this star to be a magnetic white dwarf or to have its lines rotationally broadened. | This led different authors to consider the possibility of this star to be a magnetic white dwarf or to have its lines rotationally broadened. |
Both options were considered by Karletal.(2005). who discarded the former possibility. | Both options were considered by \cite{kar05}, who discarded the former possibility. |
With the purpose of solving the fitting problem of this star. in this work we have used updated models for DA white dwarfs with effective temperatures between 6000 and 10000 K. These models were kindly provided by D. Koester. who calculated them considering. collision-induced absorption due to the presence of molecular hydrogen. | With the purpose of solving the fitting problem of this star, in this work we have used updated models for DA white dwarfs with effective temperatures between 6000 and 10000 K. These models were kindly provided by D. Koester, who calculated them considering collision-induced absorption due to the presence of molecular hydrogen. |
This effect is very significant at low temperatures and it should be taken into account for an accurate determination of the atmospheric parameters. | This effect is very significant at low temperatures and it should be taken into account for an accurate determination of the atmospheric parameters. |
Contrarily to. the results obtained by Karletal.(2005) we did not need to consider rotational broadening to achieve a good fit. | Contrarily to the results obtained by \cite{kar05} we did not need to consider rotational broadening to achieve a good fit. |
On the other hand. the southern hemisphere targets had been also studied by different authors. | On the other hand, the southern hemisphere targets had been also studied by different authors. |
Recently. Kawkaetal.(2007) derived. the atmospheric parameters for WD1544—377. WD1620—39] and WD]659— 531. which are in good agreement with our results. | Recently, \cite{kaw07} derived the atmospheric parameters for $-$ 377, $-$ 391 and $-$ 531, which are in good agreement with our results. |
Once we have derived the Zr and logg of each star. we can obtain its mass (Mwp) and cooling time (feoot) from appropriate cooling sequences. | Once we have derived the $T_{\rm eff}$ and $\log g$ of each star, we can obtain its mass $M_{\rm
WD}$ ) and cooling time $t_{\rm cool}$ ) from appropriate cooling sequences. |
We have used the cooling tracks of Salarisetal.(2000) — model SO — which consider à carbon-oxygen (C/O) core white dwarf (with. a higher abundance of O at the center of the core) with a thick hydrogen envelope on top of a helium buffer. gH)=My/M107 and g(He)=My./M107. | We have used the cooling tracks of \cite{sal00} — model S0 — which consider a carbon-oxygen (C/O) core white dwarf (with a higher abundance of O at the center of the core) with a thick hydrogen envelope on top of a helium buffer, $q({\rm H})=M_{\rm H}/M=10^{-4}$ and $q({\rm He})=M_{\rm He}/M=10^{-2}$. |
These improved cooling sequences include an accurate treatment of the crystallization process of the C/O core. including phase separation upon crystallization. together with up-to-date input physics suitable for computing white dwarf evolution. | These improved cooling sequences include an accurate treatment of the crystallization process of the C/O core, including phase separation upon crystallization, together with up-to-date input physics suitable for computing white dwarf evolution. |
In order to check the sensitivity of our results to the adopted cooling tracks. we also used the sequences of Fontaineetal.(2001) with different core compositions. | In order to check the sensitivity of our results to the adopted cooling tracks, we also used the sequences of \cite{fon01} with different core compositions. |
In a first series of calculations. C/O cores with a composition of 50/50 by mass with thick H envelopes. q(H)=1077. on top of a He buffer. g(He)=107. Were adopted. | In a first series of calculations, C/O cores with a composition of 50/50 by mass with thick H envelopes, $q({\rm H})=10^{-4}$, on top of a He buffer, $q({\rm He})=10^{-2}$, were adopted. |
We refer to these models as FO. | We refer to these models as F0. |
In the second series of calculations. cooling sequences with a pure C core and the same envelope characteristics — model Fl — were used. | In the second series of calculations, cooling sequences with a pure C core and the same envelope characteristics — model F1 — were used. |
As can be seen in Table 5.. the derived masses do not change appreciably when adopting different cooling sequences. | As can be seen in Table \ref{tab:5}, the derived masses do not change appreciably when adopting different cooling sequences. |
On the contrary. small differences can be noted in the cooling times obtained. depending on the evolutionary tracks used. | On the contrary, small differences can be noted in the cooling times obtained, depending on the evolutionary tracks used. |
This stems naturally from the different core compositions of the cooling sequences adopted here. | This stems naturally from the different core compositions of the cooling sequences adopted here. |
As can be noted by examining Table 5. considering a C/O core with equal carbon-oxygen mass fractions with thick envelopes (model FO) is quite similar to considering a C/O core with more O concentrated in the center of the core (model SO) in terms of the cooling time. | As can be noted by examining Table 5, considering a C/O core with equal carbon-oxygen mass fractions with thick envelopes (model F0) is quite similar to considering a C/O core with more O concentrated in the center of the core (model S0) in terms of the cooling time. |
Also. and as it should be expected. we obtain larger values for the cooling times when considering the pure C core sequences (model ΕΤ). since a white dwarf with a pure C core cools slower than a white dwarf with a C/O core because of the higher heat capacity of C in comparison with that of O. implying a larger amount of energy necessary to change the temperature of the core. | Also, and as it should be expected, we obtain larger values for the cooling times when considering the pure C core sequences (model F1), since a white dwarf with a pure C core cools slower than a white dwarf with a C/O core because of the higher heat capacity of C in comparison with that of O, implying a larger amount of energy necessary to change the temperature of the core. |
Some of thesewhite dwarfs have mass estimates from previous Investigations. | Some of thesewhite dwarfs have mass estimates from previous investigations. |
Silvestrietal.(2001) calculated masses from gravitational redshifts for WD0O0315-011. 13544340. 1544-377. WD1620—391. WD1659-S3 and WD2253-081. | \cite{sil01} calculated masses from gravitational redshifts for $-$ 011, $+$ 340, $-$ 377, $-$ 391, $-$ 531 and $-$ 081. |
The results of that study are compatible | The results of that study are compatible |
For our Hi-selected: sample. we make use of the Imperial IRAS Faint Source Catalogue recdshilt database (LESC) compiled from the Ηλ Faint Source Catalogue (ESC) by 7T.. | For our IR-selected sample, we make use of the Imperial IRAS Faint Source Catalogue redshift database (IIFSCz) compiled from the IRAS Faint Source Catalogue (FSC) by \cite{2009MNRAS.398..109W}. |
his is a laree of the skv) database. consisting of 60.303 galaxies selected. at. 60/2. For our analysis. we require that all galaxies have redshifts. and we include both spectroscopic and photometric redshifts in our compilation (7. discuss in. detail the accuracy of their. photometric redshifts. derived. using neural network fitting. concluding that they are accurate to. ) A total of 44.622 eaaxies in the LIPSC have a secure redshift identification. | This is a large of the sky) database consisting of 60,303 galaxies selected at $\mu$ m. For our analysis, we require that all galaxies have redshifts, and we include both spectroscopic and photometric redshifts in our compilation \citealt{2009MNRAS.398..109W} discuss in detail the accuracy of their photometric redshifts, derived using neural network fitting, concluding that they are accurate to ) A total of 44,622 galaxies in the IIFSCz have a secure redshift identification. |
We then cross matched this subsample against the GALEN AIS. resulting in a total of 25.768 galaxies observed. with both Ht and UV: this comprises our Liv-selected: sample. | We then cross matched this subsample against the GALEX AIS, resulting in a total of 25,768 galaxies observed with both IR and UV: this comprises our IR-selected sample. |
Naturally. some of the galaxies observed with GALEN were not detected due toa low UV tux. | Naturally, some of the galaxies observed with GALEX were not detected due to a low UV flux. |
We distinguished between GALEN non-detections (i.e. upper limits) and galaxies never observed with GALEN by crossmatching with a 0.6 search pacjus. ecdivalent to the size ofa GALEN tile. | We distinguished between GALEX non-detections (i.e. upper limits) and galaxies never observed with GALEX by crossmatching with a $0.6^{\circ}$ search radius, equivalent to the size of a GALEX tile. |
‘To nsure (hat redshift. evolution cllects played no significan part in the luminosity distribution. we applied alcINI cut to our sample (which will slightly reduce the number ensitv of the most. luminous systems. which are uncer-represented in the local Universe). | To ensure that redshift evolution effects played no significant part in the luminosity distribution, we applied a $z<0.1$ cut to our sample (which will slightly reduce the number density of the most luminous systems, which are under-represented in the local Universe). |
We also applied a 605m Dux limit of 0.36 Jy. which was then used. to define the value of Vii for cach galaxy in the Ht sample - this limit corresponds to the completeness limit of the LEGAS PSC. and is higher than the formal 605m Hux limit of the PSC of 0.2 Jv. | We also applied a $\mu$ m flux limit of 0.36 Jy, which was then used to define the value of $_{\mathrm{max}}$ for each galaxy in the IR sample - this limit corresponds to the completeness limit of the IRAS FSC, and is higher than the formal $\mu$ m flux limit of the FSC of 0.2 Jy. |
We also applied a minimum redshift eut ol z=0.005 (~20 Mpc). to remove any galaxies lor which peculiar motion would overwhelm the Hubble How. leading to highly uncertain distances based: upon recession velocity alone. | We also applied a minimum redshift cut of $z = 0.005$ $\sim$ 20 Mpc), to remove any galaxies for which peculiar motion would overwhelm the Hubble flow, leading to highly uncertain distances based upon recession velocity alone. |
This last cut in ellect removes EB-faint (Lin:100 L.) galaxies from the sample: the volunie-limited LVL. sample samples this region of luminosity space well however. so no information is lost overall. | This last cut in effect removes IR-faint $_{\mathrm{IR}} \leq 10^9 \;\mathrm{L}_{\sun}$ ) galaxies from the sample; the volume-limited LVL sample samples this region of luminosity space well however, so no information is lost overall. |
This near field cut also has the effect. of eliminating much of the GALEX "shredding? problem whereby nearby extended: sources are. resolved as multiple objects. resulting in artificially lowered UY Óluxes (see. e.g. η. | This near field cut also has the effect of eliminating much of the GALEX `shredding' problem whereby nearby extended sources are resolved as multiple objects, resulting in artificially lowered UV fluxes (see, e.g, \citealt{2007tS..173..267S}) ). |
ὃν comparing the UV fluxes of our LResclected sample with those of Buat et. al. ( | By comparing the UV fluxes of our IR-selected sample with those of Buat et al. ( |
2007). who used their own photometric extraction technique. we estimate that ab most 5% of our galaxies suller from photometric extraction issues (such as shrecling). | 2007), who used their own photometric extraction technique, we estimate that at most $\sim5\%$ of our galaxies suffer from photometric extraction issues (such as shredding). |
Constructing Luminosity functions consisting solely of the subset of galaxies common to both samples (3023 members). we find that the UN LE produced by our Duxes is essenially identical to that built. from. independentIy-obtained UV Iluxes. | Constructing luminosity functions consisting solely of the subset of galaxies common to both samples (302 members), we find that the UV LF produced by our fluxes is essentially identical to that built from independently-obtained UV fluxes. |
As such. we proceed. with the assumption tha Our UV fluxes are robust. | As such, we proceed with the assumption that our UV fluxes are robust. |
The final Ht. sample. after applving all the above cuts. consists of 10.252 galaxies. | The final IR sample, after applying all the above cuts, consists of 10,252 galaxies. |
To confirm that working with this subsample of the LIFSCz does not bias our results. we constructed the (monochromatic) 60/2 luminosity function. for our subsample. anc compared them to the equivalent. LEs of 2? which were constructed. using the complete sample: the LE. derived from our subsample does not dilfer significantly from those derived from the parent sample (see Fig. | To confirm that working with this subsample of the IIFSCz does not bias our results, we constructed the (monochromatic) $\mu$ m luminosity function for our subsample, and compared them to the equivalent LFs of \cite{2010MNRAS.401...35W} which were constructed using the complete sample; the LF derived from our subsample does not differ significantly from those derived from the parent sample (see Fig. |
1 for the LE. of our original. ‘unadulterated’ Lk sample). | 1 for the LF of our original, `unadulterated' IR sample). |
“Phe main dillerence is a sharper cut-olf at the most. [uminous end of the Luminosity function. for our sample. which is attributable to the high-z cut - the parent sample. having no such cut. includes many ULIRGs ane IvLIliCs (systems with Lin107?Lee and 107L.. respectively). which are very rare in the z0 Universe. | The main difference is a sharper cut-off at the most luminous end of the luminosity function for our sample, which is attributable to the $z$ cut - the parent sample, having no such cut, includes many ULIRGs and HyLIRGs (systems with $_{\mathrm{IR}} > 10^{12} \; \mathrm{L}_{\sun}$ and $10^{13} \;\mathrm{L}_{\sun}$ respectively), which are very rare in the $z\sim0$ Universe. |
The UV-selected. sample was taken from the paper by 2.. who assembled: a UV-selected. sample of galaxies to assess the relative contributions of obscured and unobscured. star formation in the local Universe. | The UV-selected sample was taken from the paper by \cite{2007ApJS..173..404B}, who assembled a UV-selected sample of galaxies to assess the relative contributions of obscured and unobscured star formation in the local Universe. |
To briefly summarise. their sample was selected. by applying a UV. cut of. FUY 17.5 mag to the GALEN All-Skv. Imaging Survey (ALS) catalogue. and cross-matchine with the LRAS PSCz in areas uncontaminated by foreground (Le. galactic*) cippus emission. | To briefly summarise, their sample was selected by applying a UV cut of FUV = 17.5 mag to the GALEX All-Sky Imaging Survey (AIS) catalogue, and cross-matching with the IRAS PSCz in areas uncontaminated by foreground (i.e. galactic) cirrus emission. |
The resulting effective area is 2210 deg? - while smaller than the laree area covered. by the HESCzZ (which. at of the sky. covers over an order of magnitude more sky. area) this is still substantial and. will avoid the clustering biases ancl sensitivity to small-scale inhomogeneities that are the weakness of pencil beam-tvpe surveys. | The resulting effective area is 2210 $^2$ - while smaller than the large area covered by the IIFSCz (which, at of the sky, covers over an order of magnitude more sky area), this is still substantial and will avoid the clustering biases and sensitivity to small-scale inhomogeneities that are the weakness of `pencil beam'-type surveys. |
Distances for the UN sample galaxies were obtained from NED. | Distances for the UV sample galaxies were obtained from NED. |
The same distance cuts as the LR-seleeted sample were applied (0.005<2 0.11. | The same distance cuts as the IR-selected sample were applied $0.005 < z < 0.1$ ). |
The low- ancl high-2 cut-olls remove S and 4 galaxies respectively from the parent sample of 606 our UV-selected: sample therefore consists of 595 ealaxies. | The low- and $z$ cut-offs remove 8 and 4 galaxies respectively from the parent sample of 606 – our UV-selected sample therefore consists of 595 galaxies. |
To augment our LR ancl UV-selected. samples in the [ow luminosity regime. we use data on a complete sample of nearby. galaxies collected by the GALEN HHIIUGS (11 Alpe Hla UV. Galaxy Survey) ancl Spitzer LVL (Local Volume Legacy) programs. | To augment our IR- and UV-selected samples in the low luminosity regime, we use data on a complete sample of nearby galaxies collected by the GALEX 11HUGS (11 Mpc $\alpha$ UV Galaxy Survey) and Spitzer LVL (Local Volume Legacy) programs. |
The sample is dominated by cdwarl ealaxies. and is thus ideal for studying the nature of systems with low SEIts. low metallicities and low dust contents. | The sample is dominated by dwarf galaxies, and is thus ideal for studying the nature of systems with low SFRs, low metallicities and low dust contents. |
UV. and mid- to far-LR Dux catalogs are published in Lee et al. ( | UV, and mid- to far-IR flux catalogs are published in Lee et al. ( |
2010) and. Dale et al. ( | 2010) and Dale et al. ( |
2010). respectively. | 2010), respectively. |
Details on the sample selection. observations. photometry are provided in those papers. and in Ixennicutt ct al. ( | Details on the sample selection, observations, photometry are provided in those papers, and in Kennicutt et al. ( |
2008). who describe the overall parent 11 Alpe sample and Lla imaging survey. | 2008), who describe the overall parent 11 Mpc sample and $\alpha$ imaging survey. |
A brief summary of the dataset is given here. | A brief summary of the dataset is given here. |
The total parent Local Volume sample. contains 436 objects. | The total parent Local Volume sample contains 436 objects. |
Galaxies are compiled. from. existing catalogs (as described. in Wennicutt et al. | Galaxies are compiled from existing catalogs (as described in Kennicutt et al. |
2008). and the selection is divided into two components. | 2008), and the selection is divided into two components. |
Tle primary component of he sample aims to be as complete as possible in its inclusion of known nearby star-forming galaxies within given limits. | The primary component of the sample aims to be as complete as possible in its inclusion of known nearby star-forming galaxies within given limits. |
It. consists of spirals ancl irregulars brighter han B = 15 mag within 11. Mpc that avoid the Galactic rlane (|h]: 20°). | It consists of spirals and irregulars brighter than B = 15 mag within 11 Mpc that avoid the Galactic plane $|b|>$ $^{o}$ ). |
Phese bounds represent the ranges within which the original surveys that provided. the bulk of our knowledge on the Local Volume galaxy population have oin shown to be relatively complete. while still spanning a enough volume to probe a representative Cross section of regestar formation properties. | These bounds represent the ranges within which the original surveys that provided the bulk of our knowledge on the Local Volume galaxy population have been shown to be relatively complete, while still spanning a large enough volume to probe a representative cross section of star formation properties. |
The secondary. component. of he sample consists of galaxies that are within 11 Alpe and | The secondary component of the sample consists of galaxies that are within 11 Mpc and |
The discovery of DII-WB. star svstems within close proximity has increased rate estimates of coalescing BBIIs. | The discovery of BH-WR star systems within close proximity has increased rate estimates of coalescing BBHs. |
There are presently (wo known svstems: NGC300 X-1. which lies at a distance of 1.8 Alpe and is composed of a~ 20A. DII anda WR star of ~26M... 2010): ICLO N-1 contains a DII of a mass al least 22... and a 35.M.. WR star. and lies within 700 kpe (Prestwichetal. | There are presently two known systems: NGC300 X-1, which lies at a distance of 1.8 Mpc and is composed of a $\sim 20 M_{\odot}$ BH and a WR star of $\sim 26
M_{\odot}$ \citep{Crowther}; IC10 X-1 contains a BH of a mass at least $23 M_{\odot}$ and a $\sim 35 M_{\odot}$ WR star, and lies within 700 kpc \citep{Prestwich}. |
2007).. As WR. stars are the progenitors of Type Ib/e supernovae. if such svstems survive the supernova explosion. DDII svstems will form acl eventually coalesce within a timescale of Gvrs (Buliketal.2011). | As WR stars are the progenitors of Type Ib/c supernovae, if such systems survive the supernova explosion, BBH systems will form and eventually coalesce within a timescale of Gyrs \citep{Bulik08}. |
. Recent results from Sloan Digital Skv Survey. have indicated that half of recent. star formation involved galaxies with low metallicity (Panterοἱal.2008).. | Recent results from Sloan Digital Sky Survey, have indicated that half of recent star formation involved galaxies with low metallicity \citep{2008MNRAS.391.1117P}. |
This has a profound effect on the coalescence rates of compact binaries containing DIIs when one considers (hat NGC300 X-1 and [010 X-1 were both formed in low metallicity environments. | This has a profound effect on the coalescence rates of compact binaries containing BHs when one considers that NGC300 X-1 and IC10 X-1 were both formed in low metallicity environments. |
survival of BBIT svstems is highly dependent on whether they can overcome (wo kev obstacles in their evolution. | Survival of BBH systems is highly dependent on whether they can overcome two key obstacles in their evolution. |
Firstly. post natal supernova kicks can disrupt a significant proportion of svstems. | Firstly, post natal supernova kicks can disrupt a significant proportion of systems. |
Secondly. orbital shrinkage during the common envelope phase when the larger star translers mass {ο ils smaller companion. can cause (he stus (o merge before they become compact objects. | Secondly, orbital shrinkage during the common envelope phase when the larger star transfers mass to its smaller companion, can cause the stars to merge before they become compact objects. |
Belezvnskietal.(2010b) have shown through population-svulhesis modeling that a lower metallicity environment can suppress (these (wo elfects. | \citet{metal}
have shown through population-synthesis modeling that a lower metallicity environment can suppress these two effects. |
Firstly. observational evidence suggests that. larger DII masses. which are produced at low metallicitv. are born with lower kick velocities (Mirabel&Rodrigues2003:Belezvuski 2010a). | Firstly, observational evidence suggests that larger BH masses, which are produced at low metallicity, are born with lower kick velocities \citep{Mirabel,bhmass}. |
. Secondly. in lower metallicity environments. slower radial expansion occurs during (he common envelope phase. (hus increasing binary retention. | Secondly, in lower metallicity environments, slower radial expansion occurs during the common envelope phase, thus increasing binary retention. |
The greater fraction of svstems that can survive. in combination with a greater detection range from more massive aud hence luminous svstenmis. has increased the detection prospects of BBIIs lor ground-based interlerometric GW detectors (Belezvuskietal.2010b). | The greater fraction of systems that can survive, in combination with a greater detection range from more massive and hence luminous systems, has increased the detection prospects of BBHs for ground-based interferometric GW detectors \citep{metal}. |
. Previous estimates of the coalescence rate of BBIIs formed through isolated. binary evolution in the field have ranged over orders of magnitude. [rom 10.| to 0.3 ?Mywr.! with a realistic value of 5x10.?AlpeMvr.| (Kalogeraetal.2007:Abacdie 2010).. | Previous estimates of the coalescence rate of BBHs formed through isolated binary evolution in the field have ranged over orders of magnitude, from $10^{-4}$ to 0.3 $^{-3}\rm{Myr}^{-1}$ with a realistic value of $5 \times 10^{-3}\, \rm{Mpc}^{-3}\rm{Myr}^{-1}$ \citep{DCO,lsc_rate}. . |
The elfect of metallicity discussed above increases the realistic estimate to 3.1x102Mpe"Myr! assuning a 50-50 mixture of solar and 104 solar metallicity and the most stringent evolutionary scenario wilh respect to svstem survival (Belczvuskietal.2010b). | The effect of metallicity discussed above increases the realistic estimate to $3.1 \times
10^{-2}\,\rm{Mpc}^{-3}\rm{Myr}^{-1}$ assuming a 50-50 mixture of solar and $10\%$ solar metallicity and the most stringent evolutionary scenario with respect to system survival \citep{metal}. |
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