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 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 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 (M_AB) 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 \times 10^8 -5 \times 10^9 M_\odot 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 build up in the LCDM model is sufficient to explain the evolution of UV LFs of LBGs along with their M* - M_AB relations, the stellar mass functions and the sSFR for 3 < z < 8.