Radio Selection of the Most Distant Galaxy Clusters

Daddi, E. and Jin, S. and Strazzullo, V. and Sargent, M. T. and Wang, T. and Ferrari, C. and Schinnerer, E. and Smolčić, Vernesa and Calabró, A. and Coogan, R. and Delhaize, J. and Delvecchio, I. and Elbaz, D. and Gobat, R. and Gu, Q. and Liu, D. and Novak, Mario and F., Valentino (2017) Radio Selection of the Most Distant Galaxy Clusters. Astrophysical Journal Letters, 846. L31-7. ISSN 2041-8205

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We show that the most distant X-ray-detected cluster known to date, Cl J1001 at zspec=2.506, hosts a strong overdensity of radio sources. Six of them are individually detected (within 10´´) in deep 0´´.75 resolution VLA 3 GHz imaging, with S3 GHz > 8μJy. Of the six, an active galactic nucleus (AGN) likely affects the radio emission in two galaxies, while star formation is the dominant source powering the remaining four. We searched for cluster candidates over the full COSMOS 2 deg2 field using radio-detected 3 GHz sources and looking for peaks in V5 density maps. Cl J1001 is the strongest overdensity by far with > 10σ, with a simple zphot > 1.5 preselection. A cruder photometric rejection of z < 1 radio foregrounds leaves Cl J1001 as the second strongest overdensity, while even using all radio sources Cl J1001 remains among the four strongest projected overdensities. We conclude that there are great prospects for future deep and wide-area radio surveys to discover large samples of the first generation of forming galaxy clusters. In these remarkable structures, widespread star formation and AGN activity of massive galaxy cluster members, residing within the inner cluster core, will ultimately lead to radio continuum as one of the most effective means for their identification, with detection rates expected in the ballpark of 0.1–1 per square degree at z ≳ 2.5. Samples of hundreds such high-redshift clusters could potentially constrain cosmological parameters and test cluster and galaxy formation models.

Item Type: Article
Keywords: galaxies, clusters, general – galaxies, evolution – galaxies, formation – galaxies, high-redshift – radio continuum, galaxies
Date: 2017
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © 2017. The American Astronomical Society. Received 2017 July 26; revised 2017 August 22; accepted 2017 August 22; published 2017 September 8.
Divisions: Faculty of Science > Department of Physics
Publisher: IOP Publishing
Depositing User: Vernesa Smolčić
Date Deposited: 08 Nov 2017 10:39
Last Modified: 20 Mar 2018 16:30

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