Galaxy Ages with Redshift z=2-4: Stellar Population Synthesis for Candidates in FourStar Galaxy Evolution Survey

TL;DR

This study estimates the ages of high-redshift galaxies using spectral energy distribution fitting, revealing that most are older than 1 Gyr and that massive galaxies tend to be older and formed earlier.

Contribution

It provides improved age constraints for galaxies at redshifts 2-4 by incorporating complex stellar populations and extinction in SED fitting, highlighting age and mass relationships.

Findings

Most galaxies at z>2.5 have ages between 1-2 Gyr.

Massive galaxies are generally older than less massive ones.

Average galaxy age does not significantly evolve between z=2 and z=4.

Abstract

Observations of large amount of massive galaxies with relatively old populations found at high redshifts are challenging galaxy formation scenarios within standard cosmology. Precise determinations of the average age of these galaxies would be useful for the discussion of this problem. Here we carry out a better constraint of the age of 200 V-shaped SED non-AGN galaxies at redshifts $2<z<4$ of the catalog of FourStar Galaxy Evolution Survey, identified by V-shape in their spectral energy distribution (SED) with a Lyman and a Balmer break. SED fitting include a main stellar population in addition to a residual younger population and extinction. The galaxies are younger at higher redshift on average. However, for the galaxies with $z>2.5$, we do not see a significant evolution of their average age, with all average ages of galaxies mostly remaining between 1 and 2 Gyr. Our research find that most massive galaxies ($\sim 10^{10} M_\odot$ ) are older (typically $>\sim 1$ Gyr old) and formed earlier than less massive galaxies in our sample.