Stellar-to-halo mass relation of cluster galaxies

In the formation of galaxy groups and clusters, the dark matter haloes containing satellite galaxies are expected to be tidally stripped in gravitational interactions with the host. We use galaxy-galaxy weak lensing to measure the average mass of dark matter haloes of satellite galaxies as a function of projected distance to the centre of the host, since stripping is expected to be greater for satellites closer to the centre of the cluster. We further classify the satellites according to their stellar mass: Assuming that the stellar component of the galaxy is less disrupted by tidal stripping, stellar mass can be used as a proxy of the infall mass. We study the stellar-to-halo mass relation of satellites as a function of the cluster-centric distance to measure tidal stripping. We use the shear catalogues of the Dark Energy Survey (DES) science verification archive, the Canada-France-Hawaii Lensing Survey (CFHTLenS) and the CFHT Stripe 82 surveys, and we select satellites from the redMaPPer catalogue of clusters. For galaxies located in the outskirts of clusters, we find a stellar-to-halo mass relation in good agreement with the theoretical expectations from Moster et al. for central galaxies. In the centre of the cluster, we find that this relation is shifted to smaller halo mass for a given stellar mass. We interpret this finding as further evidence for tidal stripping of dark matter haloes in high-density environments.

Does concentration drive the scatter in the stellar-to-halo mass relation of galaxy clusters?

Wei Cui, Jean-Paul Richard Kneib, Huanyuan Shan, Jun Zhang

Concentration is one of the key dark matter halo properties that could drive the scatter in the stellar-to-halo mass relation of massive clusters. We derive robust photometric stellar masses for a sample of brightest central galaxies (BCGs) in SDSS REDMAPPER clusters at 0.17 < z < 0.3, and split the clusters into two equal-halo mass subsamples by their BCG stellar mass M-BCG*. The weak lensing profiles Delta Sigma of the two cluster subsamples exhibit different slopes on scales below 1 h(-1) Mpc. To interpret such discrepancy, we perform a comprehensive Bayesian modelling of the two Delta Sigma profiles by including different levels of miscentring effects between the two subsamples as informed by X-ray observations. We find that the two subsamples have the same average halo mass of 1.74 x 10(14) h(-1) M-circle dot, but the concentration of the low-M-BCG* clusters is 5.87(-0.60)(+0.77), similar to 1.5 sigma smaller than that of their high-M-BCG* counterparts (6.95(-0.66)(+0.78)). Furthermore, both cluster weak lensing and cluster-galaxy cross-correlations indicate that the large-scale bias of the low-M-BCG*, low-concentration clusters are similar to 10 per cent higher than that of the high-M-BCG *, high-concentration systems, hence possible evidence of the cluster assembly bias effect. Our results reveal a remarkable physical connection between the stellar mass within 20-30 h(-1) kpc, the dark matter mass within similar to 200 h(-1) kpc, and the cosmic overdensity on scales above 10 h(-1) Mpc, enabling a key observational test of theories of co-evolution between massive clusters and their central galaxies.

OXFORD UNIV PRESS2021

The GOGREEN survey: Internal dynamics of clusters of galaxies at redshift 0.9-1.4

Hung-Hsu Chan, Pascale Jablonka

Context. The study of galaxy cluster mass profiles (M(r)) provides constraints on the nature of dark matter and on physical processes affecting the mass distribution. The study of galaxy cluster velocity anisotropy profiles (beta (r)) informs the orbits of galaxies in clusters, which are related to their evolution. The combination of mass profiles and velocity anisotropy profiles allows us to determine the pseudo phase-space density profiles (Q(r)); numerical simulations predict that these profiles follow a simple power law in cluster-centric distance.Aims. We determine the mass, velocity anisotropy, and pseudo phase-space density profiles of clusters of galaxies at the highest redshifts investigated in detail to date.Methods. We exploited the combination of the GOGREEN and GCLASS spectroscopic data-sets for 14 clusters with mass M-200 >= 10(14) M-circle dot at redshifts 0.9

EDP SCIENCES S A2021

Cold gas in the inner regions of intermediate redshift clusters

Pascale Jablonka

Determining the nature and modes of star formation at galactic scales requires an understanding of the relationship between the gas content of a galaxy and its star formation rate. Remarkable progress has been made in understanding the conversion mechanisms in field galaxies, but the cold and dense gas fueling the star formation in galaxies inside clusters has been investigated much less often. We present the first CO observations of luminous infrared galaxies (LIRGs) inside the virial radii of two intermediate redshift clusters, CL1416+4446 (z = 0.397) and CL0926+1242 (z = 0.489). We detect three galaxies at high significance (5 to 10 sigma), and provide robust estimates of their CO luminosities L'(CO). To put our results into a general context, we revisit the relation between cold and hot gas and stellar mass in nearby field and cluster galaxies. We find evidence that at fixed L-IR (or fixed stellar mass), the frequency of high L'(CO) galaxies is lower in clusters than in the field, suggesting environmental depletion of the reservoir of cold gas. The level of star formation activity in a galaxy is primarily linked to the amount of cold gas, rather than to the galaxy mass or the lookback time. In clusters, just as in the field, the conversion between gas and stars seems universal. The relation between L-IR and L'(CO) for distant cluster galaxies extends the relation of nearby galaxies to higher IR luminosities. Nevertheless, the intermediate redshift galaxies fall well within the dispersion of the trend defined by local systems. Considering that L'(CO) is generally derived from the CO(1-0) line and sensitive to the vast majority of the molecular gas in the cold interstellar medium of galaxies, but less to the part which will actually be used to form stars, we suggest that molecular gas can be stripped before the star formation rate is affected. Combining our sample with others, we find evidence for a decrease in CO towards the cluster centers. This is the first hint of an environmental impact on cold gas at intermediate redshift.

Edp Sciences S A2013

Cold gas in the inner regions of intermediate redshift clusters

Pascale Jablonka

Edp Sciences S A2013