Link between brightest cluster galaxy properties and large scale extensions of 38 DAFT/FADA and CLASH clusters in the redshift range 0.2 < z < 0.9

Abstract

Context. In the context of large-scale structure formation, clusters of galaxies are located at the nodes of the cosmic web, and continue to accrete galaxies and groups along filaments. In some cases, they show a very large extension and a preferential direction. Brightest cluster galaxies (BCGs) are believed to grow through the accretion of many small galaxies, and their structural properties are therefore expected to vary with redshift. In some cases BCGs show an orientation comparable to that of the cluster to which they belong. Aims. We analyse the morphological properties of 38 BCGs from the DAFT/FADA and CLASH surveys, and compare the position angles of their major axes to the direction of the cluster elongation at large scale (several Mpc). Methods. The morphological properties of the BCGs were studied by applying the GALFIT software to HST images and fitting the light distribution with one or two Sérsic laws, or with a Nuker plus a Sérsic law. The cluster elongations at very large scale were estimated by computing density maps of red sequence galaxies. Results. The morphological analysis of the 38 BCGs shows that in 11 cases a single Sérsic law is sufficient to account for the surface brightness, while for all the other clusters two Sérsic laws are necessary. In five cases, a Nuker plus a Sérsic law give a better fit. For the outer Sérsic component, the effective radius increases with decreasing redshift, and the effective surface brightness decreases with effective radius, following the Kormendy law. An agreement between the major axis of the BCG and the cluster elongation at large scale within ±30 deg is found for 12 clusters out of the 21 for which the PAs of the BCG and of the large-scale structure can be defined. Conclusions. The variation with redshift of the effective radius of the outer Sérsic component agrees with the growing of BCGs by accretion of smaller galaxies from z = 0.9 to 0.2, and it would be interesting to investigate this variation at higher redshift. The directions of the elongations of BCGs and of their host clusters and large scale structures surrounding them agree for 12 objects out of 21, implying that a larger sample is necessary to reach more definite conclusions.

Physical properties of brightest cluster galaxies up to redshift 1.80 based on HST data

“…Similarly, Cerulo et al (2019) did not find significant stellar mass growth between z = 0.35 and z = 0.05, suggesting that most of the BCGs stellar masses were formed by z = 0.35. Durret et al (2019) observed a possible variation with redshift of the effective radius of the outer Sérsic component of BCGs for 38 BCGs in the redshift range 0.2 ≤ z ≤ 0.9, agreeing with a scenario in which BCGs at these redshifts mostly grow by accreting smaller galaxies.…”

Ellipticity of brightest cluster galaxies as tracer of halo orientation and weak-lensing mass bias

“…The dark matter halo and the BCG are therefore thought to be aligned, as is indicated by simulations (e.g. Schneider et al 2012) and observations (Donahue et al 2016;Wittman et al 2019;Durret et al 2019). Even beyond the BCG, the distribution of the intracluster light has been shown to follow the distribution of dark matter closely (Montes & Trujillo 2019).…”

Jellyfish galaxy candidates in MACS J0717.5+3745 and 39 other clusters of the DAFT/FADA and CLASH surveys

“…First, we looked at the histograms of all the redshifts available in a large zone around each cluster (for the DAFT/FADA clusters, these histograms were given by Guennou et al 2014 andDurret et al 2016); for the other clusters we retrieved all the redshifts available in NED and drew their histogram in the approximate cluster redshift range. We also looked at the matter distribution based on a weak lensing analysis by Martinet et al (2016) or on the shape of the red sequence density map by Durret et al (2016Durret et al ( , 2019. For clusters with at least 10 spectroscopic redshifts available within the HST images analysed in the present paper, we looked at the proportion of jellyfish galaxy candidates relative to the relaxation state of the cluster.…”

“…For each cluster, we identify galaxies with spectroscopic redshifts in the range previously chosen to draw galaxy density maps (Durret et al 2016(Durret et al , 2019 and roughly corresponding to an interval of ±0.02 around the corresponding cluster redshift. This translates into a velocity range indicated in Table 1 for each cluster, expressed in units of the corresponding cluster velocity dispersion (computed in Sect.…”

“…In some cases, we give below a few indications on specific galaxies when we think it is useful and we indicate if clusters are merging whenever this information is available. In particular, we mention if the positions of the jellyfish candidates lie in the direction of the general elongation of the cluster, defined both from the position angle of the brightest cluster galaxy, from the alignment of the brightest cluster galaxies, and from the red-sequence galaxy density maps drawn by Durret et al (2016Durret et al ( , 2019 when available. This direction should trace the orientation of the filamentary regions, at large scale, where each cluster is embedded, and along which one would expect the largest galaxy infall to happen (e.g.…”