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

Journal article

We present the results of a search for galaxy clusters and groups in the ∼2 deg2 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 3×10−16ergcm−2s−1 in the 0.5–2 keV range, and identify 247 X-ray groups with M200c=8×1012--3×1014M⊙ 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.

Authors: Gozaliasl, G; Finoguenov, A; Tanaka, M; Dolag, K; Montanari, F

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 483
• Issue: 3
• Pages: 3545-3565
• Publication date: 2018-11-27
• Acceptance date: 2018-11-16
• DOI: 10.1093/mnras/sty3203
• EISSN: 1365-2966
• ISSN: 0035-8711
• Keywords: FFR; X-rays: galaxies: clusters; galaxies: evolution; galaxies: clusters: general; galaxies: groups: general; galaxies: stellar content; galaxies: statistics