Star-formation rates of cluster galaxies: nature vs nurture

TL;DR

This study investigates how star formation rates in cluster galaxies depend on environment and stellar mass at intermediate-to-high redshifts, finding mass to be the dominant factor influencing star formation activity.

Contribution

It provides the first detailed analysis of SFR and sSFR dependence on environment and mass for cluster galaxies at $0.4<z<0.9$, using spectral energy distribution fitting.

Findings

SFR correlates with stellar mass at $z hickapprox 0.9$.

No significant dependence of SFR on environment was observed.

Mass is the primary driver of star formation in cluster galaxies at these redshifts.

Abstract

We analyzed 17 galaxy clusters, and investigated, for the first time, the dependence of the SFR and sSFR as a function of projected distance (as a proxy for environment) and stellar mass for cluster galaxies in an intermediate-to-high redshift range ($0.4 < z < 0.9$). We used up to nine flux points (BVRIZYJHKs magnitudes), its errors and redshifts to compute M$_{\rm{star}}$, SFR and sSFR through spectral energy distribution fitting technique. We use a z-dependent sSFR value to distinguish star-forming (SF) from quiescent galaxies. To analyse the SFR and sSFR history we split our sample in two redshift bins: galaxies at $0.4 < z < 0.6$ and $0.6 < z < 0.9$. We separate the effects of environment and stellar mass on galaxies by comparing the properties of star-forming and quiescent galaxies at fixed environment (projected radius) and fixed stellar mass. For the selected spectroscopic sample of more than 500 galaxies, the well-known correlation between SFR and $M_{\rm star}$ is already in place at $z \sim 0.9$, for both SF and quenched galaxies. Our results are consistent with no evidence that SFR (or sSFR) depends on environment, suggesting that for cluster galaxies at an intermediate-to-high redshift range, mass is the primary characteristic that drives SFR.