Cosmic star formation: constraints on the galaxy formation models

Abstract

ABSTRACT We study the evolution of the cosmic star formation in the universe by computingthe luminosity density (in the UV, B, J, and K bands) and the stellar mass densityof galaxies in two reference models of galaxy evolution: the pure-luminosity evolution(PLE) model developed by Calura & Matteucci (2003) and the semi-analytical model(SAM) of hierarchical galaxy formation by Menci et al. (2002). The former includesa detailed description of the chemical evolution of galaxies of different morphologicaltypes; it does not include any number evolution of galaxies whose number densityis normalized to the observed local value. On the other hand, the SAM includes astrong density evolution following the formation and the merging histories of the DMhaloes hosting the galaxies, as predicted by the hierarchical clustering scenario, butit does not contain morphological classification nor chemical evolution. Our resultssuggest that at low-intermediate redshifts (z 2.5. At such redshiftsthe PLE predictions tend to overestimate the present data in the B band whereas theSAM tends to underestimate the observed UV luminosity density. As for the stellarmass density, the PLE picture predicts that nearly 50% and 85% of the present stellarmass are in place at z ∼ 4 and z ∼ 1, respectively. According to the hierarchicalSAM, 50% and 60% of the present stellar mass are completed at z ∼ 1.2 and z = 1,respectively. Both predictions fit the observed stellar mass density evolution up toz = 1. At z > 1, the PLE and SAM models tend to overestimate and underestimatethe observed values, respectively. We discuss the origin of the similarities and of thediscrepanciesbetween the two models, and the role of observationaluncertainties (suchas dust extinction) in comparing models with observations.Key words: Galaxies: formation and evolution; Galaxies: fundamental parameters.