Discovery and cosmological implications of SPT-CL J2106-5844, the most massive known cluster at z>1
Using the South Pole Telescope (SPT), we have discovered the most massive known galaxy cluster at z>1, SPT-CL J2106-5844. In addition to producing a strong Sunyaev-Zel'dovich (SZ) effect signal, this system is a luminous X-ray source and its numerous constituent galaxies display spatial and...
Published in: | The Astrophysical Journal |
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Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
IOPScience
2011
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Subjects: | |
Online Access: | https://orca.cardiff.ac.uk/id/eprint/33412/ https://doi.org/10.1088/0004-637X/731/2/86 |
Summary: | Using the South Pole Telescope (SPT), we have discovered the most massive known galaxy cluster at z>1, SPT-CL J2106-5844. In addition to producing a strong Sunyaev-Zel'dovich (SZ) effect signal, this system is a luminous X-ray source and its numerous constituent galaxies display spatial and color clustering, all indicating the presence of a massive galaxy cluster. Very Large Telescope and Magellan spectroscopy of 18 member galaxies shows that the cluster is at z = 1.132(+0.002) (–0.003.) Chandra observations obtained through a combined HRC-ACIS GTO program reveal an X-ray spectrum with an Fe K line redshifted by z = 1.18 ± 0.03. These redshifts are consistent with the galaxy colors found in optical, near-infrared, and mid-infrared imaging. SPT-CL J2106-5844 displays extreme X-ray properties for a cluster having a core-excluded temperature of T(X) = 11.0(+2.6) (–1.9) keV and a luminosity (within r (500)) of L(X) (0.5-2.0 keV) = (13.9 ± 1.0) × 10(44) erg s(–1). The combined mass estimate from measurements of the SZ effect and X-ray data is M (200) = (1.27 ± 0.21) × 10(15) h (–1) (70) M ☉. The discovery of such a massive gravitationally collapsed system at high redshift provides an interesting laboratory for galaxy formation and evolution, and is a probe of extreme perturbations of the primordial matter density field. We discuss the latter, determining that, under the assumption of ΛCDM cosmology with only Gaussian perturbations, there is only a 7% chance of finding a galaxy cluster similar to SPT-CL J2106-5844 in the 2500 deg(2) SPT survey region and that only one such galaxy cluster is expected in the entire sky. |
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