Ultra-red Galaxies Signpost Candidate Protoclusters at High Redshift

Abstract

(2018) 'Ultra-red galaxies signpost candidate protoclusters at high redshift.', Astrophysical journal., 862 (2). p. 96.Further information on publisher's website:https://doi.org/10.3847/1538-4357/aacc25Publisher's copyright statement: c 2018. The American Astronomical Society. All rights reserved. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractWe present images obtained with LABOCA of a sample of 22 galaxies selected via their red Herschel SPIRE colors. We aim to see if these luminous, rare, and distant galaxies are signposting dense regions in the early universe. Our 870 μm survey covers an area of ≈1 deg 2 down to an average rms of -3.9 mJy beam 1 , with our five deepest maps going ≈2×deeper still. We catalog 86 dusty star-forming galaxies (DSFGs) around our "signposts," detected above a significance of 3.5σ. This implies a ) DSFGs, excluding our signposts, when comparing our number counts to those in "blank fields." Thus, we are 99.93% confident that our signposts are pinpointing overdense regions in the universe, and ≈95% [50%] confident that these regions are overdense by a factor of at least 1.5× [2×]. Using template spectral energy distributions (SEDs) and SPIRE/LABOCA photometry, we derive a median photometric redshift of z=3.2±0.2 for our signposts, with an inter-quartile range of z=2.8-3.6, somewhat higher than expected for ∼850 μm selected galaxies. We constrain the DSFGs that are likely responsible for this overdensity to within  D | | z 0.65 of their respective signposts. These "associated" DSFGs are radially distributed within (physical) distances of 1.6±0.5 Mpc from their signposts, have median star formation rates (SFRs) of » ´- ( ) M 1.0 0.2 10 yr 3 1 (for a Salpeter stellar inital mass function) and median gas reservoirs of´ M 1.7 10 11. These candidate protoclusters have average total SFRs of at least » ´- ( ) M 2.3 0.5 10 yr 3 1and space densities of ∼9×10 −7 Mpc −3 , consistent with the idea that their constituents may evolve to become massive early-type galaxies in the centers of the rich galaxy clusters we see today.

ALMA unveils wider environment of distant red protocluster core

“…Of the 6 LABOCA sources reported by Lewis et al within 3 arcmin of the 10 central, confirmed members of the DRC, our ALMA imaging spectroscopy confirms 4 new members of the protocluster at z = 4 (2 towards a single LABOCA source), while 2 are shown via robust line detections to lie at other, unknown redshifts along the line of sight, and 1 is shown to be a blank sub-mm field. This rate of associations is in line with the ∼2.15× overdensity predicted by Lewis et al (2018), whose individual photometric redshift estimates are shown to have been useful.…”

“…The field of LABOCA source H was found to be devoid of continuum emission and it is therefore likely that the LABOCA detection was spurious, as already hinted by the empty Herschel SPIRE maps reported by Lewis et al (2018). ALMA 97-GHz line-free continuum emission with zeroth-moment spectral-line emission overlaid as contours in green (blue for D) for LABOCA sources C-H.…”

“…We report new ALMA observations of the z = 4 protocluster known as the DRC, selected initially by Ivison et al (2016) via its extreme far-IR colours, and reported as a site of intense cluster-scale star formation by Oteo et al (2018), Lewis et al (2018), and Long et al (2020).…”

“…Imaging at 870 μm of a much wider field, centred on the DRC, was presented by Lewis et al (2018). These LABOCA data exploited the ultrared galaxy as a signpost to a potentially dense region of the early Universe, and were obtained several years before the core was shown to comprise multiple starburst galaxies.…”

Revealing dust-obscured star formation in CLJ1449+0856, a cluster at z = 2

“…clusters that are still in the process of forming), allowing for more robust determination of whether there is a reversal at high redshift (e.g. Andreon et al 2014, Clements et al 2014, Bleem et al 2015, Alexander et al 2016, Franck & McGaugh 2016, Cai et al 2017, Daddi et al 2017, Mantz et al 2017, Umehata et al 2017, Casasola et al 2018, Lewis et al 2018, Oteo et al 2018, Zeballos et al 2018 CL J1449+0856 (hereafter CLJ1449, RA= 222.3083 Dec=8.9392) is one of the highest redshift, fully virialized, mature X-ray emitting clusters known. The cluster was first identified as an over-density of red galaxies during Spitzer observations of the so called 'Daddi fields' (Daddi et al 2000).…”