Using public data from the NEWFIRM Medium-Band Survey ( NMBS ) and the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey ( CANDELS ) , we investigate the population of massive galaxies at z > 3 .
The main aim of this work is to identify the potential progenitors of z \sim 2 compact , massive , quiescent galaxies , furthering our understanding of the onset and evolution of massive galaxies .
Our work is enabled by high-resolution images from CANDELS data and accurate photometric redshifts , stellar masses , and star formation rates ( SFRs ) from 37-band NMBS photometry .
The total number of massive galaxies at z > 3 is consistent with the number of massive quiescent galaxies at z \sim 2 , implying that the SFRs for all of these galaxies must be much lower by z \sim 2 .
We discover four compact , massive , quiescent galaxies at z > 3 , pushing back the time for which such galaxies have been observed .
However , the volume density for these galaxies is significantly less than that of galaxies at z < 2 with similar masses , SFRs , and sizes , implying that additional compact , massive , quiescent galaxies must be created in the intervening \sim 1 Gyr between z = 3 and z = 2 .
We find five star-forming galaxies at z \sim 3 that are compact ( R _ { e } < 1.4 kpc ) and have stellar mass M _ { * } > 10 ^ { 10.6 } M _ { \odot } ; these galaxies are likely to become members of the massive , quiescent , compact galaxy population at z \sim 2 .
We evolve the stellar masses and SFRs of each individual z > 3 galaxy adopting five different star formation histories ( SFHs ) and studying the resulting population of massive galaxies at z = 2.3 .
We find that declining or truncated SFHs are necessary to match the observed number density of massive , quiescent galaxies at z \sim 2 , whereas a constant SFH would result in a number density significantly smaller than observed .
All of our assumed SFHs imply number densities of compact , massive , and quiescent galaxies at z \sim 2 that are consistent with the observed number density .
Better agreement with the observed number density of compact , massive , quiescent galaxies at z \sim 2 is obtained if merging is included in the analysis and better still if star formation quenching is assumed to shortly follow the merging event , as implied by recent models of formation of massive , quiescent galaxies .