Chandra centres for COSMOS X-ray galaxy groups: differences in stellar properties between central dominant and offset brightest group galaxies
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Date
2019-03
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Journal Article
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yes
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Abstract
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 3×10⁻¹⁶erg cm⁻² s⁻¹ in the 0.5–2 keV range, and identify 247 X-ray groups with M₂₀₀꜀=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.
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published
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483 (3)
Pages / Article No.
3545 - 3565
Publisher
Oxford University Press
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Subject
galaxies: clusters: general; galaxies: evolution; galaxies: groups: general; galaxies: statistics; galaxies: stellar content; X-rays: galaxies: clusters
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03613 - Lilly, Simon (emeritus) / Lilly, Simon (emeritus)
Notes
It was possible to publish this article open access thanks to a Swiss National Licence with the publisher.