Selection of massive evolved galaxies at $3 \leq z \leq 4.5$ in the CANDELS fields

TL;DR

This study identifies and analyzes massive evolved galaxies at redshifts 3 to 4.5 using CANDELS data, comparing their number densities and stellar masses with models, and exploring implications for galaxy evolution and quenching mechanisms.

Contribution

It introduces a multi-method selection of massive evolved galaxies at high redshift and compares their properties with theoretical models, highlighting discrepancies and potential evolutionary insights.

Findings

Number densities of massive galaxies at z=3.4 and 4.7 are estimated.

Models tend to underestimate the observed number and mass densities.

Halo masses suggest efficient star formation and possible quenching mechanisms.

Abstract

Using the CANDELS photometric catalogs for the HST/ACS and WFC3, we identified massive evolved galaxies at $3 < z < 4.5$, employing three different selection methods. We find the comoving number density of these objects to be $\sim 2 \times 10^{-5}$ and $8 \times 10^{-6}Mpc^{-3}$ after correction for completeness for two redshift bins centered at $z=3.4, 4.7$. We quantify a measure of how much confidence we should have for each candidate galaxy from different selections and what are the conservative error estimates propagated into our selection. Then we compare the evolution of the corresponding number densities and their stellar mass density with numerical simulations, semi-analytical models, and previous observational estimates, which shows slight tension at higher redshifts as the models tend to underestimate the number and mass densities. By estimating the average halo masses of the candidates ($M_h \approx 4.2, 1.9, 1.3 \times 10^{12} M_\odot$ for redshift bins centered at $z=3.4, 4.1, 4.7$), we find them to be consistent with halos that were efficient in turning baryons to stars and were relatively immune to the feedback effects and on the verge of transition into hot-mode accretion. This can suggest the relative cosmological starvation of the cold gas followed by an overconsumption phase in which the galaxy consumes the available cold gas rapidly as one of the possible drivers for the quenching of the massive evolved population at high redshift.