A GALEX/Spitzer survey of the Cl0016+16 supercluster at z=0.55: acceleration of the onset of star-formation in satellite groups

TL;DR

This study uses Spitzer and GALEX data to analyze star formation in the Cl0016+16 supercluster at z=0.55, revealing that satellite groups experience accelerated star formation likely due to pre-processing, without individual rate enhancement.

Contribution

It provides new evidence for pre-processing effects in satellite groups within a supercluster, highlighting environmental influences on star formation during galaxy infall.

Findings

Star formation rates are similar in cluster and field galaxies.

Pockets of accelerated star formation are present in the supercluster.

Estimated total star formation rate is approximately 850 solar masses per year.

Abstract

We present the results of a panoramic (15 Mpc-scale) survey of the Cl0016+16 supercluster (z=0.55) using Spitzer Space Telescope MIPS 24um and Galaxy Evolution Explorer near-UV (2500A; NUV) imaging. The supercluster regions probed are characterised by several dense nodes connected by a pronounced intermediate-density filamentary structure. We have studied the mid-IR and NUV properties of potential cluster members within a Dz=0.1 photometric redshift slice, compared to an identical blank field selection. We have two main findings: (a) the star-formation rates of individual star-forming galaxies throughout the cluster are not significantly different to identically selected field galaxies, and (b) the cluster harbours pockets of 'accelerated' activity where galaxies have an enhanced probability of undergoing star formation. This observation could be explained in a simple model of 'pre-processing' of galaxies during cluster infall: galaxies in satellite groups have an increased chance of having star-formation triggered via gravitational tidal interactions compared to their counterparts in the field, but there is no environmental mechanism boosting the individual star-formation rates of galaxies. We estimate a lower-limit for the total star-formation rate of galaxies in the supercluster as ~850 Msun/yr (field corrected). If this rate is maintained over the typical infall time of a few Gyr, then the infall population could contribute ~1-2x10^12 Msun of stellar mass to the structure.