Mining the gap: evolution of the magnitude gap in X-ray galaxy groups from the 3-square-degree XMM coverage of CFHTLS

Abstract

We present a catalog of 129 X-ray galaxy groups, covering a redshift range 0.04 < z < 1.23, selected in the ∼3 deg 2 part of the CFHTLS W1 field overlapping XMM observations performed under the XMM-LSS project. We carry out a statistical study of the redshift evolution out to redshift one of the magnitude gap between the first and the second brightest cluster galaxies of a well defined mass-selected group sample. We find that the slope of the relation between the fraction of groups and the magnitude gap steepens with redshift, indicating a larger fraction of fossil groups at lower redshifts. We find that 22.2 ± 6% of our groups at z ≤ 0.6 are fossil groups. We compare our results with the predictions of three semi-analytic models based on the Millennium simulation. The intercept of the relation between the magnitude of the brightest galaxy and the value of magnitude gap becomes brighter with increasing redshift. This trend is steeper than the model predictions which we attribute to the younger stellar age of the observed brightest cluster galaxies. This trend argues in favor of stronger evolution of the feedback from active galactic nuclei at z < 1 compared to the models. The slope of the relation between the magnitude of the brightest cluster galaxy and the value of the gap does not evolve with redshift and is well reproduced by the models, indicating that the tidal galaxy stripping, put forward as an explanation of the occurrence of the magnitude gap, is both a dominant mechanism and sufficiently well modeled.

Evolution of the cluster optical galaxy luminosity function in the CFHTLS: breaking the degeneracy between mass and redshift

“…In the following sections, we will compare our candidate cluster catalogue to previously published cluster catalogues on the Wide fields of CFHTLS. We will first make a comparison with other optically detected cluster candidate catalogues from Licitra et al (2016) and Ford et al (2015), and with Xray detected cluster catalogues from Gozaliasl et al (2014) and Mirkazemi et al (2015).…”

“…The Gozaliasl et al (2014) catalogue covers an area of 3 deg 2 inside the CFHTLS W1 field and includes 135 X-ray detected groups and clusters up to z = 1.1, while the Mirkazemi et al (2015) catalogue was built by pointing at given optically selected cluster candidates; it includes 196 X-ray detected groups and clusters up to z = 1.1 in the CFHTLS W1, W2, and W4.…”

“…However, neither Gozaliasl et al (2014) nor Mirkazemi et al (2015) provide the completeness of their catalogue for given mass and redshift. Thus they cannot be used to properly compute a selection function of our algorithm, but only give us insights into how AMASCFI performed on the CFHTLS T0007 data.…”

“…We detect a total of 3743 cluster candidates up to redshift z ∼ 1.1 and estimate the selection function of this sample by applying the same algorithm to numerical simulations based on lightcones from the Millennium simulation by Springel et al (2005) and modified by Henriques et al (2012). We derive a mass for each cluster candidate using a richness-mass relation calibrated on the X-ray clusters of Gozaliasl et al (2014) and Mirkazemi et al (2015) that are also detected by our algorithm. We compute cluster GLFs for all galaxies, and also for early and late types separately.…”

Evolution of the galaxy luminosity function in progenitors of fossil groups

“…Jones et al (2003) reported 8% to 20% of all galaxy groups have the same X-ray luminosity as fossil groups. The redshift evolution of the fossil fraction has been studied by Gozaliasl et al (2014), finding that fossil groups constitute 22 ± 6% and 13 ± 7% of massive galaxy groups (M 200 ∼ 10 13.5 M h −1 ) at z ≤ 0.6 and 0.6 < z < 1.2, respectively. In the semianalytic halo catalogue, based on the Millennium simulation, ∼7.2 ± 0.2 per cent of massive groups are fossils (Dariush et al 2007).…”