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

Abstract

Abstract Combined observations from UV to IR wavelengths are necessary to fully account for the star formation in galaxy clusters. Low-mass galaxies with log ( M ∗ / M ⊙ ) < 10 are typically not individually 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 hosting quiescent, passive galaxies. To account for these undetected galaxies, we measure the total light emerging from GALEX/near-UV stacks of galaxy clusters at z = 0.5–1.6. Combined with existing measurements from Spitzer, WISE, and Herschel, we study the average UV through far-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 place strong constraints on derived stellar-to-halo mass ratios at z < 1, which anticorrelate 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 semianalytical models.