Relation Between Stellar Mass and Star Formation Activity in Galaxies

TL;DR

This study investigates how star formation activity varies with stellar mass in galaxies from redshift 0.2 to 2, revealing that massive galaxies formed most of their stars earlier than less massive ones.

Contribution

It provides a detailed analysis of the evolution of star formation rates as a function of stellar mass across a wide redshift range, extending previous studies with new combined data.

Findings

Massive galaxies contribute less to the total SFRD at all redshifts.

The SFRD increases steeply for massive galaxies up to z~2.

Lower mass galaxies show a plateau in SFRD at z~1.

Abstract

For a mass-selected sample of 66544 galaxies with photometric redshifts from the Cosmic Evolution Survey (COSMOS), we examine the evolution of star formation activity as a function of stellar mass in galaxies. We estimate the cosmic star formation rates (SFR) over the range 0.2 < z < 1.2, using the rest-frame 2800 A flux (corrected for extinction). We find the mean SFR to be a strong function of the galactic stellar mass at any given redshift, with massive systems (log (M/M(Sun)) > 10.5) contributing less (by a factor of ~ 5) to the total star formation rate density (SFRD). Combining data from the COSMOS and Gemini Deep Deep Survey (GDDS), we extend the SFRD-z relation as a function of stellar mass to z~2. For massive galaxies, we find a steep increase in the SFRD-z relation to z~2; for the less massive systems, the SFRD which also increases from z=0 to 1, levels off at z~1. This implies that the massive systems have had their major star formation activity at earlier epochs (z > 2) than the lower mass galaxies. We study changes in the SFRDs as a function of both redshift and stellar mass for galaxies of different spectral types. We find that the slope of the SFRD-z relation for different spectral type of galaxies is a strong function of their stellar mass. For low and intermediate mass systems, the main contribution to the cosmic SFRD comes from the star-forming galaxies while, for more massive systems, the evolved galaxies are the most dominant population.