Strong lensing in the inner halo of galaxy clusters

We present an axially symmetric formula to calculate the probability of finding gravitational arcs in galaxy clusters, being induced by their massive dark matter haloes, as a function of clusters redshifts and virial masses. The formula includes the ellipticity of the clusters dark matter potential by using a pseudo-elliptical approximation. The probabilities are calculated and compared for two dark matter halo profiles, the Navarro, Frenk and White (NFW) and the non-singular- isothermal-sphere (NSIS). We demonstrate the power of our formulation through a Kolmogorov-Smirnov (KS) test on the strong lensing statistics of an X-ray bright sample of low-redshift Abell clusters. This KS test allows us to establish limits on the values of the concentration parameter for the NFW profile (c(Delta)) and the core radius for the NSIS profile (r(c)), which are related to the lowest cluster redshift (z(cut)) where strong arcs can be observed. For NFW dark matter profiles, we infer cluster haloes with concentrations that are consistent to those predicted by Lambda CDM simulations. As for NSIS dark matter profiles, we find only upper limits for the clusters core radii and thus do not rule out a purely SIS model. For alternative mass profiles, our formulation provides constraints through zcut on the parameters that control the concentration of mass in the inner region of the clusters haloes. We find that zcut is expected to lie in the 0.0-0.2 redshift, highlighting the need to include very low-z clusters in samples to study the clusters mass profiles.

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

Hubble Frontier Fields: the geometry and dynamics of the massive galaxy cluster merger MACSJ0416.1-2403

Hakim Atek, Benjamin Yvan Alexandre Clement, David Richard Harvey, Mathilde Jauzac, Jean-Paul Richard Kneib, Richard Massey, Markus Rexroth, Johan Richard

We use a joint optical/X-ray analysis to constrain the geometry and history of the ongoing merging event in the massive galaxy cluster MACSJ0416.1-2403 (z = 0.397). Our investigation of cluster substructure rests primarily on a combined strong-and weak-lensing mass reconstruction based on the deep, high-resolution images obtained for the Hubble Frontier Fields initiative. To reveal the system's dynamics, we complement this lensing analysis with a study of the intracluster gas using shallow Chandra data, and a three-dimensional model of the distribution and motions of cluster galaxies derived from over 100 spectroscopic redshifts. The multiscale grid model obtained from our combined lensing analysis extends the high-precision strong-lensing mass reconstruction recently performed to cluster-centric distances of almost 1 Mpc. Our analysis detects the two well-known mass concentrations in the cluster core. A pronounced offset between collisional and collisionless matter is only observed for the SW cluster component, while excellent alignment is found for the NE cluster. Both the lensing analysis and the distribution of cluster light strongly suggest the presence of a third massive structure, almost 2 arcmin SW of the cluster centre. Since no X-ray emission is detected in this region, we conclude that this structure is non-virialized and speculate that it might be part of a large-scale filament almost aligned with our line of sight. Combining all evidence from the distribution of dark and luminous matter, we propose two alternative scenarios for the trajectories of the components of MACSJ0416.1-2403. Upcoming deep X-ray observations that allow the detection of shock fronts, cold cores, and sloshing gas (all key diagnostics for studies of cluster collisions) will allow us to test, and distinguish between these two scenarios.

Wiley-Blackwell2015

CODEX clusters: Survey, catalog, and cosmology of the X-ray luminosity function

Johan Comparat, Ghazaleh Erfanianfar, Jean-Paul Richard Kneib

Context. Large area catalogs of galaxy clusters constructed from ROSAT All-Sky Survey provide the basis for our knowledge of the population of clusters thanks to long-term multiwavelength efforts to follow up observations of these clusters.Aims. The advent of large area photometric surveys superseding previous, in-depth all-sky data allows us to revisit the construction of X-ray cluster catalogs, extending the study to lower cluster masses and higher redshifts and providing modeling of the selection function.Methods. We performed a wavelet detection of X-ray sources and made extensive simulations of the detection of clusters in the RASS data. We assigned an optical richness to each of the 24 788 detected X-ray sources in the 10 382 square degrees of the Baryon Oscillation Spectroscopic Survey area using red sequence cluster finder redMaPPer version 5.2 run on Sloan Digital Sky Survey photometry. We named this survey COnstrain Dark Energy with X-ray (CODEX) clusters.Results. We show that there is no obvious separation of sources on galaxy clusters and active galactic nuclei (AGN) based on the distribution of systems on their richness. This is a combination of an increasing number of galaxy groups and their selection via the identification of X-ray sources either by chance or by groups hosting an AGN. To clean the sample, we use a cut on the optical richness at the level corresponding to the 10% completeness of the survey and include it in the modeling of the cluster selection function. We present the X-ray catalog extending to a redshift of 0.6.Conclusions. The CODEX suvey is the first large area X-ray selected catalog of northern clusters reaching fluxes of 10(-13) ergs s(-1) cm(-2). We provide modeling of the sample selection and discuss the redshift evolution of the high end of the X-ray luminosity function (XLF). Our results on z< 0.3 XLF agree with previous studies, while we provide new constraints on the 0.3< z< 0.6 XLF. We find a lack of strong redshift evolution of the XLF, provide exact modeling of the effect of low number statistics and AGN contamination, and present the resulting constraints on the flat CDM.