An extended Herschel drop-out source in the center of AS1063, a 'normal' dusty galaxy at z=6.1 or SZ substructures?

TL;DR

This paper reports the discovery of a Herschel drop-out source in galaxy cluster AS1063, likely a moderately luminous star-forming galaxy at z=6.1, possibly lensed, providing insight into typical dusty galaxies at the end of reionization.

Contribution

It presents the identification and analysis of a high-redshift, moderately luminous dusty galaxy, possibly lensed, expanding understanding of early universe galaxy populations.

Findings

Detected a Herschel drop-out source with no PACS/SPIRE counterparts.

Identified a z=6.107 galaxy possibly associated with the source.

Estimated star formation rate of 80-260 solar masses per year.

Abstract

In the course of our 870um APEX/LABOCA follow up of the Herschel Lensing Survey we have detected a source in AS1063 (RXC J2248.7-4431), that has no counterparts in any of the Herschel PACS/SPIRE bands, it is a Herschel 'drop-out' with S_870/S_500>0.5. The 870um emission is extended and centered on the brightest cluster galaxy suggesting either a multiply imaged background source or substructure in the Sunyaev-Zel'dovich (SZ) increment due to inhomogeneities in the hot cluster gas of this merging cluster. We discuss both interpretations with emphasis on the putative lensed source. Based on the observed properties and on our lens model we find that this source could be the first SMG with a moderate far infrared luminosity (L_FIR<10^12 L_sol) detected so far at z>4. In deep HST observations we identified a multiply imaged z~6 source and we measured its spectroscopic redshift z=6.107 with VLT/FORS. This source could be associated with the putative SMG but it is most likely offset spatially by 10-30kpc and they could be interacting galaxies. With a FIR luminosity in the range [5-15]x10^{11} L_sol corresponding to a star formation rate in the range [80-260]M_sol/yr, this SMG would be more representative than the extreme starbursts usually detected at z>4. With a total magnification of ~25 it would open a unique window to the 'normal' dusty galaxies at the end of the epoch of reionization.