A physical model for the redshift evolution of high-z Lyman-break galaxies

Abstract

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 (LFs) 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 LFs of LBGs. We find the fraction of baryons that gets converted into stars remains nearly constant for z≥4 but shows an increase for z > 4. However, the rate of converting baryons into stars does not evolve significantly in the redshift range 3 ≤ z ≤ 8. Our model further successfully explains the M*-UV luminosity (MAB) correlations of LBGs. While our model predictions of stellar mass functions compare well with the inferred data from observations at the low-mass end, we need to invoke the Eddington bias to fit the high-mass end. At any given redshift, we find the sSFR to be constant over the stellar mass range 5 × 108-5 × 109M⊙ and the redshift evolution of sSFR is well approximated by a form (1 + z)2.4 for 3 ≤z ≤ 8 which is consistent with observations. Thus, we find that dark matter halo buildup in the ΛCDM model is sufficient to explain the evolution of UV LFs of LBGs along with their M*-MAB relations, the stellar mass functions and the sSFR for 3 ≤ z ≤ 8. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.