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Published March 2019 | Supplemental Material + Published + Accepted Version
Journal Article Open

Chandra centres for COSMOS X-ray galaxy groups: differences in stellar properties between central dominant and offset brightest group galaxies

Abstract

We present the results of a search for galaxy clusters and groups in the ∼2 deg^2 of the COSMOS field using all available X-ray observations from the XMM–Newton and Chandra observatories. We reach an X-ray flux limit of 3×10^(−16) erg cm^(−2)s^(−1) in the 0.5–2 keV range, and identify 247 X-ray groups with M_(200c) = 8×10^(12) -3×10^(14)M⊙ at a redshift range of 0.08 ≤ z < 1.53, using the multiband photometric redshift and the master spectroscopic redshift catalogues of the COSMOS. The X-ray centres of groups are determined using high-resolution Chandra imaging. We investigate the relations between the offset of the brightest group galaxies (BGGs) from halo X-ray centre and group properties and compare with predictions from semi-analytic models and hydrodynamical simulations. We find that BGG offset decreases with both increasing halo mass and decreasing redshift with no strong dependence on the X-ray flux and SNR. We show that the BGG offset decreases as a function of increasing magnitude gap with no considerable redshift-dependent trend. The stellar mass of BGGs in observations extends over a wider dynamic range compared to model predictions. At z < 0.5, the central dominant BGGs become more massive than those with large offsets by up to 0.3 dex, in agreement with model prediction. The observed and predicted log-normal scatter in the stellar mass of both low- and large-offset BGGs at fixed halo mass is ∼0.3 dex.

Additional Information

© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2018 November 16. Received 2018 November 15; in original form 2018 April 4. Published: 27 November 2018. This work has been supported by grants from the Finnish Academy of Science to the University of Helsinki and the Euclid project, decision numbers 266918 and 1295113. GG wishes to thank Mr. Donald Smart for very useful comments. ST acknowledges support from the ERC Consolidator Grant funding scheme (project Context, grant no. 648179). The Cosmic Dawn Center is funded by the Danish National Research Foundation. We used data of the Millennium simulation from the web application providing online access, constructed as activities of the German Astrophysics Virtual Observatory.

Attached Files

Published - sty3203.pdf

Accepted Version - 1812.01604.pdf

Supplemental Material - sty3203_supplemental_file.txt

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Created:
August 19, 2023
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October 20, 2023