Dusty starbursts and the formation of elliptical galaxies: A SCUBA-2 survey of a z=1.46 cluster

TL;DR

This study uses deep SCUBA-2 observations to identify a significant overdensity of dust-obscured ultra-luminous infrared galaxies in a z=1.46 galaxy cluster, linking intense star formation to early-type galaxy formation.

Contribution

It provides the first detailed sub-millimeter survey of a z=1.46 cluster, revealing a high concentration of U/LIRGs and their role in cluster galaxy evolution.

Findings

Overdensity of sub-millimeter sources in the cluster core

Cluster U/LIRGs have luminosities around 10^12 L_sun

Star formation rate supports rapid galaxy evolution at z~1.5

Abstract

We report the results of a deep SCUBA-2 850- and 450-$\mu$m survey for dust-obscured ultra-luminous infrared galaxies (U/LIRGs) in the field of the z=1.46 cluster XCS J2215.9-1738. We detect a striking overdensity of sub-millimeter sources coincident with the core of this cluster: $\sim 3-4 \times$ higher than expected in a blank field. We use the likely radio and mid-infrared counterparts to show that the bulk of these sub-millimeter sources have spectroscopic or photometric redshifts which place them in the cluster and that their multi-wavelength properties are consistent with this association. The average far-infrared luminosities of these galaxies are $(1.0\pm0.1) \times 10^{12} L_{\odot}$, placing them on the U/LIRG boundary. Using the total star formation occurring in the obscured U/LIRG population within the cluster we show that the resulting mass-normalized star-formation rate for this system supports previous claims of a rapid increase in star-formation activity in cluster cores out to $z\sim1.5$, which must be associated with the on-going formation of the early-type galaxies which reside in massive clusters today.