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in Wainscoat et al. ( | in Wainscoat et al. ( |
1992). | 1992). |
Πωπονον, the model marked “truncated exponential” has a stellar density that ouly rises exponentiallv inwards down to 3.5 kpe. from which »oiut it falls off linearly such that at the οσο it is zero. | However, the model marked “truncated exponential” has a stellar density that only rises exponentially inwards down to 3.5 kpc, from which point it falls off linearly such that at the centre it is zero. |
This approximates to a Freeman type IT disc with a ceutral role and is known as an iuner truncated disc. | This approximates to a Freeman type II disc with a central hole and is known as an inner truncated disc. |
The model predicts that a purely exponential disc hat continues iuto the ceutre should rise iucreasinely steeply with decreasing longitude: however. the measured counts clearly do not do this. | The model predicts that a purely exponential disc that continues into the centre should rise increasingly steeply with decreasing longitude; however, the measured counts clearly do not do this. |
The truucated model docs. rowever, reproduce the shape very well. | The truncated model does, however, reproduce the shape very well. |
A full discussion of the exact fori of the iuner dise is bevoud the scope of this paper. as data further from the plane are required: rowever. this result is in aerecinent with the fiudiues frou he analysis of the COBE/DIRBE surface rightness maps (e.g. Freudenreich 1998). | A full discussion of the exact form of the inner disc is beyond the scope of this paper, as data further from the plane are required; however, this result is in agreement with the findings from the analysis of the /DIRBE surface brightness maps (e.g. Freudenreich 1998). |
Tuner truncated discs are very conmuuon iu barred spirals. | Inner truncated discs are very common in barred spirals. |
Olta e al. ( | Ohta et al. ( |
1990) looked. at six carly-type spirals and fouud that all had. Freciman type II discs when looking perpendicular to the plane. | 1990) looked at six early-type spirals and found that all had Freeman type II discs when looking perpendicular to the plane. |
BagecttOO ct al. ( | Baggett et al. ( |
1996) show that barred galaxies are a factor of two. or more. more likely than non-barred Calaxics to have an inner truncated disc. | 1996) show that barred galaxies are a factor of two, or more, more likely than non-barred Galaxies to have an inner truncated disc. |
They also note that an increasing number of bars is beiug found iu galaxies previously classified as non-barred. so this percentage Is likely to rise. | They also note that an increasing number of bars is being found in galaxies previously classified as non-barred, so this percentage is likely to rise. |
The large-scale απλο counts in the plane are very roticeable. | The large-scale asymmetry counts in the plane are very noticeable. |
Positive longitudes consistently have far more counts than negative longitudes. | Positive longitudes consistently have far more counts than negative longitudes. |
Furthermore. the shape of the counts is very different at positive ancl negative ongitudes. so the form cannot be explained bv simply naking the inner Galaxy elliptical. | Furthermore, the shape of the counts is very different at positive and negative longitudes, so the form cannot be explained by simply making the inner Galaxy elliptical. |
Frou about /=27° to he Calactic Centre the counts are flat. whereas between f=ϱἳ aud /=Lad" they are reduced by a factor 2. | From about $l=27^\circ$ to the Galactic Centre the counts are flat, whereas between $l=0^\circ$ and $l=-18^\circ$ they are reduced by a factor 2. |
This asvuuuetry is ercater iu the 6=07 strip than in the b|=(0.757 strip because the relative contribution of the uw will be larecr a b=0 | This asymmetry is greater in the $b=0^\circ$ strip than in the $|b|=0.75^\circ$ strip because the relative contribution of the bar will be larger at $b=0^\circ$. |
"The disc will coutribute about of the counts at /220° in the pluie but. as is shown in the previous section. the dise is svuuuetric. | The disc will contribute about of the counts at $l=20^\circ$ in the plane but, as is shown in the previous section, the disc is symmetric. |
Hence. when the disc is subtracted from the ii plane counts the asvuuuetrics between positive and negative longitudes iu the remaining counts (ie. those from the inner Calaxy coniponents) become enornious. | Hence, when the disc is subtracted from the in plane counts the asymmetries between positive and negative longitudes in the remaining counts (i.e. those from the inner Galaxy components) become enormous. |
The peak due to the bulge at 7—(7 is hardly seen at all in the in-plane strip. whereas it is clearly evident in the off-plaue counts. | The peak due to the bulge at $l=0^\circ$ is hardly seen at all in the in-plane strip, whereas it is clearly evident in the off-plane counts. |
This is due in part to the strong extinction within a few hundred pe of the Galactic Coutre (GC) which drastically reduces the counts in the plane (Wamunersleyv et al. | This is due in part to the strong extinction within a few hundred pc of the Galactic Centre (GC) which drastically reduces the counts in the plane (Hammersley et al. |
1999). | 1999). |
Hence. the rapid increase iu star deusitv near the CC is masked. | Hence, the rapid increase in star density near the GC is masked. |
However. the |=77 b= Ine of sight uus far enough away from the GC ot to be affected x the verv high extinction near the GC. aud here the bulge contributes about of the counts to my=9 (Fie. | However, the $l=7^\circ$ $b=0^\circ$ line of sight runs far enough away from the GC not to be affected by the very high extinction near the GC, and here the bulge contributes about of the counts to $m_K=9$ (Fig. |
B2 in Wamunersley et al. | B2 in Hammersley et al. |
1999). | 1999). |
At exeater absolute longitudes the bulge quickly dics away. providing a negligible coutribution for |/|>107. | At greater absolute longitudes the bulge quickly dies away, providing a negligible contribution for $|l|>10^\circ$. |
Therefore. there has to be another component in the plane taking its place at ereater absolute longitudes to make the counts almost flat up to /=27° where it then stops quite suddenly. | Therefore, there has to be another component in the plane taking its place at greater absolute longitudes to make the counts almost flat up to $l=27^\circ$, where it then stops quite suddenly. |
This component contributes around of the detected sources. so if just be a major feature in the iuner Galaxy. | This component contributes around of the detected sources, so it must be a major feature in the inner Galaxy. |
This component is principally seen at positive longitudes. extending from the bulee up to /=27° and somewhat less at negative longitudes. | This component is principally seen at positive longitudes, extending from the bulge up to $l=27^\circ$ and somewhat less at negative longitudes. |
This makes the component extremely asvuuuetrie as secu from the Sun. far nore so than the triaxial bulec. | This makes the component extremely asymmetric as seen from the Sun, far more so than the triaxial bulge. |
Clearly. oue explanation for the asvununetrv im the counts would be extinction. | Clearly, one explanation for the asymmetry in the counts would be extinction. |
This has au important role as a bar would be expected to have dust lanes ou its leading edges (Calbet el al. | This has an important role as a bar would be expected to have dust lanes on its leading edges (Calbet el al. |
1996) and will be discussed im Section l: however. extinction cau only reduce the nmuubers of stars. whereas here there is clearly an extra population iu the plane. | 1996) and will be discussed in Section \ref{.ext}; however, extinction can only reduce the numbers of stars, whereas here there is clearly an extra population in the plane. |
Iu W9L a vine. bv itself. is shown not to explain the in-plane features. | In H94, a ring, by itself, is shown not to explain the in-plane features. |
A ring would be expected to produce | A ring would be expected to produce |
Molecular line observations of several massive-star forming regions show evidence for star-forming accretion flows around small HII regions (Guilloteauetal.1983;Ho&HaschickZhangetal.1998;Sollins2004,2005a,b;Beltran 2006).. | Molecular line observations of several massive-star forming regions show evidence for star-forming accretion flows around small HII regions \citep{Guilloteau1983,
HoHaschick1986, Keto1987a, Keto1987b, Keto1988, HoYoung1996, ZhangHo1997, Young1998,
ZhangHoOhashi1998, Sollins2004, Sollins2005a, Sollins2005b, Beltran2006}. |
These HII regions | These HII regions |
EARA-EST host fellowship while this work was carried out and acknowledges the TAP for hospitality. | EARA-EST host fellowship while this work was carried out and acknowledges the IAP for hospitality. |
CE is partly supported by the Swiss Sunburst Fund. | CE is partly supported by the Swiss Sunburst Fund. |
Funding for the SDSS has been provided by the Alfred P. Sloan Foundation. the Participating Institutions. the National Science Foundation. the US Department of Energy. the National Aeronautics and Space Administration. the Japanese Monbukagakusho. the Max Planck Society. and the Higher Education Funding Council for England. | Funding for the SDSS has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. |
The SDSS Web site is httpz/Awww.sdss.org. | The SDSS Web site is http://www.sdss.org. |
The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. | The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. |
The Participating Institutions are the American Museum of Natural History. the Astrophysical Institute Potsdam. the University of Basel. Cambridge University. Case Western Reserve University. he University of Chicago. Drexel University. Fermilab. the Institute for Advanced Study. the Japan Participation Group. Johns Hopkins University. the Joint Institute for Nuclear Astrophysics. he Kavli Institute for Particle Astrophysics and Cosmology. he Korean Scientist Group. the Chinese Academy of Sciences. Los Alamos National Laboratory. the Max Planck Institute for Astronomy. the Max Planck Institute for Astrophysics. New Texico State University. Ohio State University. the University of Pittsburgh. the University of Portsmouth. Princeton University. the US Naval Observatory. and the University of Washington. | The Participating Institutions are the American Museum of Natural History, the Astrophysical Institute Potsdam, the University of Basel, Cambridge University, Case Western Reserve University, the University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences, Los Alamos National Laboratory, the Max Planck Institute for Astronomy, the Max Planck Institute for Astrophysics, New Mexico State University, Ohio State University, the University of Pittsburgh, the University of Portsmouth, Princeton University, the US Naval Observatory, and the University of Washington. |
Baugh et al. | Baugh et al. |
model. | model. |
We first compare the model predictions for the luminosity function in the UV at ;=3.2 =Gand: =10 with observations. and use this to set up definitions of bright and faint LBGs. ( | We first compare the model predictions for the luminosity function in the UV at $z=3$ , $z=6$ and $z=10$ with observations, and use this to set up definitions of bright and faint LBGs. ( |
For a more detailed comparison with observed LBG luminosity functions see ?..) | For a more detailed comparison with observed LBG luminosity functions see \citealt{Lacey10b}. .) |
We then present some illustrative galaxy formation histories for present day galaxies which had LBG progenitors. | We then present some illustrative galaxy formation histories for present day galaxies which had LBG progenitors. |
Finally we show the probability that a present-day galaxy had an LBG progenitor and that a present-day halo hosted an LBG. | Finally we show the probability that a present-day galaxy had an LBG progenitor and that a present-day halo hosted an LBG. |
As outlined in the Introduction. the Lyman-break technique relies on colour-colour selection to identify galaxies within a particular redshift range. which is set by the redshifted Lyman-break spectral feature falling between two of the filters used to image the galaxies. | As outlined in the Introduction, the Lyman-break technique relies on colour-colour selection to identify galaxies within a particular redshift range, which is set by the redshifted Lyman-break spectral feature falling between two of the filters used to image the galaxies. |
In the model we ean make predictions for the galaxy population at any desired redshift by construction and so there is no need to apply any colour selection. | In the model we can make predictions for the galaxy population at any desired redshift by construction and so there is no need to apply any colour selection. |
Hence. we will use the far UV (1500À luminosity as our criterion to identify samples of Lyman-break galaxies. | Hence, we will use the far UV ) luminosity as our criterion to identify samples of Lyman-break galaxies. |
We focus our attention on three redshifts. 2= 3.2=6 and >=10. which are representative of the range covered by current LBG studies (222).. | We focus our attention on three redshifts, $z=3$, $z=6$ and $z=10$, which are representative of the range covered by current LBG studies \citep{Ste03,Bou07a,Bou10}. |
? presented predictions for the rest-frame UV luminosity function at 2=3. | \cite{Baugh05} presented predictions for the rest-frame UV luminosity function at $z=3$. |
Here we revisit this comparison. adding new observational data at +=3 and going to z=10 (see also 2)). | Here we revisit this comparison, adding new observational data at $z=3$ and going to $z=10$ (see also \citealt{Lacey10b}) ). |
In Fig. | In Fig. |
| we show the predicted rest-frame 1500A lluminosity function at >=3. 2=6 and ς=10. including the effects of dust extinction. calculated in a self-consistent way using the predicted scale lengths of the disk and bulge components and the metallicity of the cold gas. | \ref{LF} we show the predicted rest-frame $1500$ luminosity function at $z=3$, $z=6$ and $z=10$, including the effects of dust extinction, calculated in a self-consistent way using the predicted scale lengths of the disk and bulge components and the metallicity of the cold gas. |
The model matches the observational data at z=3. to within the scatter between datasets. is in good agreement with the measurement by ? at 2=6. and is consistent with the tentative measurement and upper limits estimated by ?. at +=10. | The model matches the observational data at $z=3$, to within the scatter between datasets, is in good agreement with the measurement by \cite{Bou07a}
at $z=6$, and is consistent with the tentative measurement and upper limits estimated by \cite{Bou10} at $z=10$. |
Following the common practice in observational studies. we define a characteristic luminosity £744 using the observed position of the break in the UV luminosity unetion at 2=3. | Following the common practice in observational studies, we define a characteristic luminosity $L^{*}_{UV}$ using the observed position of the break in the UV luminosity function at $z=3$. |
We define a galaxy as a bright LBG if its UV luminosity is brighter than £;-,- and as a faint LBG if its UV uminosity exceeds 0.1L;«4- (a sample which includes the bright LBG sample. but which is dominated in number by galaxies close o the luminosity cut). | We define a galaxy as a bright LBG if its UV luminosity is brighter than $L^{*}_{UV}$ and as a faint LBG if its UV luminosity exceeds $0.1 L^{*}_{UV}$ (a sample which includes the bright LBG sample, but which is dominated in number by galaxies close to the luminosity cut). |
We apply this definition at all redshifts. | We apply this definition at all redshifts. |
Note hat ἐν is taken to be the characteristic luminosity at zz3 found by ? (corresponding to αν=20.3|5logh in our cosmology). | Note that $L^{*}_{UV}$ is taken to be the characteristic luminosity at $z \approx 3$ found by \cite{Ste99}
(corresponding to $M^{*}_{UV}=-20.3+5{\rm log}h$ in our cosmology). |
In Fig. | In Fig. |
| we show where the O.1£;-,- and L;-,- limits lie using vertical lines. | \ref{LF} we show where the $0.1 L^{*}_{UV}$ and $L^{*}_{UV}$ limits lie using vertical lines. |
We note in passing that there is substantial evolution in both he observed and predicted UV luminosity functions between +=5 and 2= 6. | We note in passing that there is substantial evolution in both the observed and predicted UV luminosity functions between $z=3$ and $z=6$ . |
The observed characteristic luminosity L4. αϊ 2= GCM19.5|Slogh in our cosmology. 24) is nearly a magnitude fainter than the =3EJ value of Lj. | The observed characteristic luminosity $L^{*}_{UV,z=6}$ at $z=6$ $M^{*}_{UV,z=6}=-19.5+5{\rm log}h$ in our cosmology, \citealt{Bou07a}) ) is nearly a magnitude fainter than the $z=3$ value of $L^{*}_{UV}$. |
The number density of galaxies seen at the >=3EJ value of L;-,- drops by around a factor of 5 between >=3 and:=6. | The number density of galaxies seen at the $z=3$ value of $L^{*}_{UV}$ drops by around a factor of $5$ between $z=3$ and $z=6$. |
Αι.=10. the abundance of galaxies with this luminosity is predicted to be several hundred times lower than at 2=3. | At $z=10$, the abundance of galaxies with this luminosity is predicted to be several hundred times lower than at $z=3$. |
A comprehensive study of the evolution of the LBG luminosity function. including a more detailed comparison with observational data. is presented in 2.. | A comprehensive study of the evolution of the LBG luminosity function, including a more detailed comparison with observational data, is presented in \cite{Lacey10b}. |
As examples of the different galaxy formation and merger histories which can produce bright LBGs. we plot in the left panels of Fig. | As examples of the different galaxy formation and merger histories which can produce bright LBGs, we plot in the left panels of Fig. |
2 galaxy merger trees for three present-day galaxies. | \ref{GMT} galaxy merger trees for three present-day galaxies. |
The mass of he galaxies increases down the page. | The mass of the galaxies increases down the page. |
The trees are constructed by runningCEM with many output redshifts. | The trees are constructed by running with many output redshifts. |
We stop plotting he trees at >=6 or when a branch falls below a minimum galaxy mass (in stars and cold gas) of 1055.ΑΙ. | We stop plotting the trees at $z=6$ or when a branch falls below a minimum galaxy mass (in stars and cold gas) of $10^{6}
h^{-1}M_{\odot}$. |
A branch or trunk of he tree is plotted at each output redshift using a circle. | A branch or trunk of the tree is plotted at each output redshift using a circle. |
The size of he circle is proportional to the stellar mass of the galaxy and the colour reflects the type of galaxy: green for a faint LBG. red for a bright LBG and blue otherwise. | The size of the circle is proportional to the stellar mass of the galaxy and the colour reflects the type of galaxy: green for a faint LBG, red for a bright LBG and blue otherwise. |
The galaxy trees are plotted in the following way. | The galaxy trees are plotted in the following way. |
Stepping back in time from 2=0. at each merger we plot the most massive branch on the left and the other branches to the right of this. | Stepping back in time from $z=0$, at each merger we plot the most massive branch on the left and the other branches to the right of this. |
The main progenitor branch is hence the leftmost plotted branch raced back from 2=0 in this way. | The main progenitor branch is hence the leftmost plotted branch traced back from $z=0$ in this way. |
Note that at 2.>0. the main progenitor branch does not necessarily represent the most massive progenitor across the whole tree at a given epoch. | Note that at $z>0$, the main progenitor branch does not necessarily represent the most massive progenitor across the whole tree at a given epoch. |
The argest progenitor at any time could jump from one branch of the galaxy tree to another. so its selection would not necessarily detine a smooth path back in redshift. | The largest progenitor at any time could jump from one branch of the galaxy tree to another, so its selection would not necessarily define a smooth path back in redshift. |
We have chosen to plot examples which have at least one LBG in the most massive (leftmost) progenitor branch. | We have chosen to plot examples which have at least one LBG in the most massive (leftmost) progenitor branch. |
In the first example (Fig. | In the first example (Fig. |
2. top left). we show the galaxymerger tree for a galaxy which at >=0 has a stellar mass of Al,=2.5.10°AI. and has a bright LBG progenitor at >=6. | \ref{GMT} top left), we show the galaxymerger tree for a galaxy which at $z=0$ has a stellar mass of $M_{*}=2.5\times10^{9} h^{-1}M_{\odot}$ and has a bright LBG progenitor at $z=6$. |
In the second example (Fig. | In the second example (Fig. |
2. middle left). we show a ealaxy with A,—6.6.10175.ΣΑΙ. at >=0 with a bright LBG progenitor at both 2=6 and +=3. | \ref{GMT} middle left), we show a galaxy with $M_{*}=6.6\times10^{10} h^{-1}M_{\odot}$ at $z=0$ with a bright LBG progenitor at both $z=6$ and $z=3$. |
In the third example (Fig. | In the third example (Fig. |
bottom left). we show the galaxy merger tree for a galaxy with Al,22.4«105.AL. at z=0 with a bright LBG progenitor at 5=6. | \ref{GMT} bottom left), we show the galaxy merger tree for a galaxy with $M_{*}=2.1\times10^{11} h^{-1}M_{\odot}$ at $z=0$ with a bright LBG progenitor at $z=6$. |
Note that these trees are purely illustrative examples. chosen to show the range of complexity of the trees. and are not intended to be a statistically representative sample. | Note that these trees are purely illustrative examples, chosen to show the range of complexity of the trees, and are not intended to be a statistically representative sample. |
The right-hand panels of Fig. | The right-hand panels of Fig. |
2. show the evolution of various properties of the galaxy in the most massive progenitor branch. | \ref{GMT} show the evolution of various properties of the galaxy in the most massive progenitor branch. |
The upper inset or subpanel in each case shows the bulge-to-total stellar mass ratio. | The upper inset or subpanel in each case shows the bulge-to-total stellar mass ratio. |
If present. a vertical line in this panel marks the epoch when the most massive progenitor ceased to be a central galaxy and became a satellite. | If present, a vertical line in this panel marks the epoch when the most massive progenitor ceased to be a central galaxy and became a satellite. |
In the examples plotted here. this only happens in the ease of the least massive galaxy tree shown (upper right Fig. 23 | In the examples plotted here, this only happens in the case of the least massive galaxy tree shown (upper right Fig. \ref{GMT}) ), |
at 2~1.1. | at $z \sim 1.1$. |
The main right-hand panel shows the UV luminosity of the most massive progenitor. in units of ἐν Cred line: see right axis for units) and its stellar mass (blue symbols). cold gas mass (green symbols). stellar mass formed in bursts (red symbols) and host dark halo mass (black symbols: see left axis for units). | The main right-hand panel shows the UV luminosity of the most massive progenitor, in units of $L^{*}_{UV}$ (red line; see right axis for units) and its stellar mass (blue symbols), cold gas mass (green symbols), stellar mass formed in bursts (red symbols) and host dark halo mass (black symbols; see left axis for units). |
In the case of the least massive galaxy (Fig. | In the case of the least massive galaxy (Fig. |
2. top right). the most massive progenitor experiences a burst at 2=6 which makes it a bright LBG. | \ref{GMT}
top right), the most massive progenitor experiences a burst at $z=6$ which makes it a bright LBG. |
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