The Herschel Filament: a signature of the environmental drivers of galaxy evolution during the assembly of massive clusters at z=0.9

TL;DR

This paper reports the discovery of a 2.5 Mpc infrared-bright galaxy filament connecting two galaxy clusters at z=0.9, highlighting active star formation and mass assembly during cluster formation.

Contribution

It presents the first detailed observation of an infrared-bright filament linking galaxy clusters at high redshift, illustrating environmental effects on galaxy evolution.

Findings

Infrared luminosity of the filament is ~5x10^12 Lsun.

Estimated star formation rate in the filament is ~900 Msun/yr.

The filament connects two massive clusters, indicating ongoing mass assembly.

Abstract

We have discovered a 2.5 Mpc (projected) long filament of infrared-bright galaxies connecting two of the three ~5x10^14 Msun clusters making up the RCS 2319+00 supercluster at z=0.9. The filament is revealed in a deep Herschel Spectral and Photometric Imaging REceiver (SPIRE) map that shows 250-500um emission associated with a spectroscopically identified filament of galaxies spanning two X-ray bright cluster cores. We estimate that the total (8-1000um) infrared luminosity of the filament is Lir~5x10^12 Lsun, which, if due to star formation alone, corresponds to a total SFR 900 Msun/yr. We are witnessing the scene of the build-up of a >10^15 Msun cluster of galaxies, seen prior to the merging of three massive components, each of which already contains a population of red, passive galaxies that formed at z>2. The infrared filament demonstrates that significant stellar mass assembly is taking place in the moderate density, dynamically active circumcluster environments of the most massive clusters at high-redshift, and this activity is concomitant with the hierarchical build-up of large scale structure.