Measuring the Total Ultraviolet Light from Galaxy Clusters at z=0.5-1.6: The Balance of Obscured and Unobscured Star-Formation

TL;DR

This study combines UV to IR observations to quantify star formation in galaxy clusters at z=0.5-1.6, revealing the balance between obscured and unobscured star formation and providing constraints on stellar-to-halo mass ratios.

Contribution

It presents the first measurement of total UV through IR light from galaxy clusters at these redshifts, including low-mass galaxies, and compares observations with theoretical models.

Findings

Unobscured star formation fraction aligns with field galaxies.

Tentative decrease in unobscured star formation at z~0.5.

Stellar-to-halo mass ratios anti-correlate with halo mass.

Abstract

Combined observations from UV to IR wavelengths are necessary to fully account for the star-formation in galaxy clusters. Low mass (log M/Msun<10) galaxies are typically not individualy detected, particularly at higher redshifts (z~1-2) where galaxy clusters are undergoing rapid transitions from hosting mostly active, dust-obscured star-forming galaxies to quiescent, passive galaxies. To account for these undetected galaxies, we measure the total light emerging from GALEX/NUV stacks of galaxy clusters between z=0.5-1.6. Combined with existing measurements from Spitzer, WISE, and Herschel, we study the average UV through far-infrared (IR) spectral energy distribution (SED) of clusters. From the SEDs, we measure the total stellar mass and amount of dust-obscured and unobscured star-formation arising from all cluster-member galaxies, including the low mass population. The relative fraction of unobscured star-formation we observe in the UV is consistent with what is observed in field galaxies. There is tentative evidence for lower than expected unobscured star-formation at z~0.5, which may arise from rapid redshift evolution in the low mass quenching efficiency in clusters reported by other studies. Finally, the GALEX data places strong constraints on derived stellar-to-halo mass ratios at z<1 which anti-correlate with the total halo mass, consistent with trends found from local X-ray observations of clusters. The data exhibit steeper slopes than implementations of the cluster star-formation efficiency in semi-analytical models.