Star Formation in Intermediate Redshift 0.2 < z < 0.7 Brightest Cluster Galaxies

TL;DR

This study investigates star formation and AGN activity in Brightest Cluster Galaxies at intermediate redshifts, finding low but sustained star formation rates and evidence of AGN fueled by cold gas, supporting hierarchical galaxy growth models.

Contribution

It provides multi-wavelength analysis of BCGs at 0.2<z<0.7, revealing persistent low-level star formation and AGN activity, and supports hierarchical formation theories.

Findings

Low and constant specific star formation rate (sSFR) across redshifts.

AGN activity correlates with star formation, both fueled by cold gas.

Star formation is not a major growth channel for BCGs at z<1.

Abstract

We present a multi-wavelength photometric and spectroscopic study of 42 Brightest Cluster Galaxies (BCGs) in two samples of galaxy clusters chosen for a gravitational lensing study. The study's initial sample combines 25 BCGs from the Cluster Lensing and Supernova Survey with Hubble (CLASH) sample and 37 BCGs from the Sloan Giant Arcs Survey (SGAS) with a total redshift range of 0.2 < z < 0.7. Using archival GALEX, Hubble Space Telescope, Wide-field Infrared Survey Explorer, Herschel, and Very Large Array data we determine the BCGs' stellar mass, radio power, and star formation rates. The radio power is higher than expected if due to star formation, consistent with the BCGs being active galactic nucleus (AGN)-powered radio sources. This suggests that the AGN and star formation are both fueled by cold gas in the host galaxy. The specific star formation rate (sSFR) is low and constant with redshift. The mean sSFR is 9.42 * 10^-12 yr^-1, which corresponds to a mass doubling time of 105 billion years. These findings are consistent with models for hierarchical formation of BCGs, which suggest that star formation is no longer a significant channel for galaxy growth for z < 1. Instead, stellar growth (of the order of a factor of at least two) during this period is expected to occur mainly via minor dry mergers