“School of Astronomy”Back to Papers Home
Back to Papers of School of Astronomy
|Paper IPM / Astronomy / 15489||
We present the results of a search for galaxy clusters and groups in the â¼2 square degree 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 3Ã10â16ergscmâ2sâ1 in 0.5-2 keV range, and identify 247 X-ray groups with M200c=8Ã1012â3Ã1014Mâ at a redshift range of 0.08â¤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 0.3dex, in agreement with model prediction. The observed and predicted lognormal scatter in the stellar mass of both low- and large-offset BGGs at fixed halo mass is â¼0.3dex.
Download TeX format
|back to top|