May 16, 2000
We use hydrodynamic cosmological simulations to predict the star formation properties of high-redshift galaxies (z=2-6) in five variants of the inflationary cold dark matter scenario, paying particular attention to z=3, the redshift of the largest "Lyman-break galaxy" (LBG) samples. Because we link the star formation timescale to the local gas density, the rate at which a galaxy forms stars is governed mainly by the rate at which it accretes cooled gas from the surrounding medium. At z=3, star formation in most of the simulated galaxies is steady on 200 Myr timescales, and the instantaneous star formation rate (SFR) is correlated with total stellar mass. However, there is enough scatter in this correlation that a sample selected above a given SFR threshold may contain galaxies with a fairly wide range of masses. The redshift history and global density of star formation in the simulations depend mainly on the amplitude of mass fluctuations in the underlying cosmological model. The three models whose mass fluctuation amplitudes agree with recent analyses of the Lyman-alpha forest also reproduce the observed luminosity function of LBGs reasonably well, though the dynamic range of the comparison is small and the theoretical and observational uncertainties are large. The models with higher and lower amplitudes appear to predict too much and too little star formation, respectively, though they are not clearly ruled out. The intermediate amplitude models predict SFR ~ 30-40 Msun/yr for galaxies with a surface density 1 per arcmin^2 per unit redshift at z=3. They predict much higher surface densities at lower SFR, and significant numbers of galaxies with SFR > 10 Msun/yr at z >= 5.
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August 12, 1999
We review theoretical approaches to the study of galaxy formation, with emphasis on the role of hydrodynamic simulations in modeling the high redshift galaxy population. We present new predictions for the abundance of star-forming galaxies in the Lambda + cold dark matter model (Omega_m=0.4, Omega_L=0.6), combining results from several simulations to probe a wide range of redshift. At a threshold density of one object per arcmin^2 per unit z, these simulations predict galaxie...
June 26, 2000
Using semi-analytic models of galaxy formation set within the Cold Dark Matter (CDM) merging hierarchy, we investigate several scenarios for the nature of the high-redshift ($z \ga 2$) Lyman-break galaxies (LBGs). We consider a ``collisional starburst'' model in which bursts of star formation are triggered by galaxy-galaxy mergers, and find that a significant fraction of LBGs are predicted to be starbursts. This model reproduces the observed comoving number density of bright ...
December 20, 2001
Data on galaxies at high redshift, identified by the Lyman-break photometric technique, can teach us about how galaxies form and evolve. The stellar masses and other properties of such Lyman break galaxies (LBGs) depend sensitively on the details of star formation. In this paper we consider three different star formation prescriptions, and use semi-analytic methods applied to the now-standard $\Lambda$CDM theory of hierarchical structure formation to show how these assumption...
March 1, 2002
The cosmic star formation history in Cold Dark Matter dominated cosmological scenarios is studied by means of hydrodynamical numerical simulations. In particular, we explore a low density model with a Lambda-term and two high density models with different power spectra, all of them being spatially flat. Our simulations employ a fully nonlinear N-body and Eulerian hydrodynamics algorithm with a model for star formation and supernovae feedback that depends on two phenomenologic...
November 12, 2003
We study the photometric properties of Lyman-break galaxies (LBGs) formed by redshift z=3 in a set of large cosmological smoothed-particle hydrodynamics simulations of the Lambda cold dark matter (CDM) model. Our numerical simulations include radiative cooling and heating with a uniform UV background, star formation, supernova feedback, and a phenomenological model for galactic winds. Analysing a series of simulations of varying boxsize and particle number allows us to isolat...
December 11, 2006
We present a self-consistent, semi-analytical LCDM model of star formation and reionization. For the cosmological parameters favored by the WMAP data, our models consistently reproduce the optical depth to reionization, redshift of reionization and the observed luminosity functions (LF) and hence the star formation rate (SFR) density at 3<z<6 for a reasonable range of model parameters. While simple photoionization feedback produces the correct shape of LF at z = 6, for $z = 3...
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We present a galaxy formation model to understand the evolution of stellar mass (M*) - UV luminosity relations, stellar mass functions and specific star formation rate (sSFR) of Lyman Break Galaxies (LBGs) along with their UV luminosity functions in the redshift range 3 < z < 8. Our models assume a physically motivated form for star formation in galaxies and model parameters are calibrated by fitting the observed UV luminosity functions (LFs) of LBGs. We find the fraction of ...
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The number density and clustering properties of Lyman-break galaxies (LBGs) observed at redshift $z\sim 3$ are best explained by assuming that they are associated with the most massive haloes at $z\sim 3$ predicted in hierarchical models of structure formation. In this paper we study, under the same assumption, how star formation and chemical enrichment may have proceeded in the LBG population. A consistent model, in which the amount of cold gas available for star formation m...
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