Mass distribution in the core of MACS J1206

Abstract

We present a new strong lensing analysis of the galaxy cluster MACS J1206.2−0847 (MACS 1206), at z = 0.44, using deep spectroscopy from CLASH-VLT and VLT/MUSE archival data in combination with imaging from the Cluster Lensing and Supernova survey with Hubble. MUSE observations enable the spectroscopic identification of 23 new multiply imaged sources, extending the previous compilations by a factor of approximately five. In total, we use the positional measurements of 82 spectroscopic multiple images belonging to 27 families at z = 1.0 − 6.1 to reconstruct the projected total mass distribution of MACS 1206. Remarkably, 11 multiple images are found within 50 kpc of the brightest cluster galaxy, making this an unprecedented set of constraints for the innermost projected mass distribution of a galaxy cluster. We thus find that, although dynamically relaxed, the smooth matter component (dark matter plus hot gas) of MACS 1206 shows a significant asymmetry, which closely follows the asymmetric distribution of the stellar component (galaxy members and intracluster light). We determine the value of the innermost logarithmic slope of the projected total mass density profile and find it to be close to the canonical Navarro-Frenk-White value. We demonstrate that this quantity is very robust against different parametrizations of the diffuse mass component; however, this is not the case when only one central image is used in the mass reconstruction. We also show that the mass density profile from our new strong lensing model is in very good agreement with dynamical and X-ray measurements at larger radii, where they overlap.

Strong lensing models of eight CLASH clusters from extensive spectroscopy: Accurate total mass reconstructions in the cores

“…Since merging clusters or systems with high asymmetries in their mass distributions cannot reproduce the observed positions of all multiple images with only one smooth component (see e.g. Lagattuta et al 2017;Caminha et al 2017b), we gradually increased the complexity of our models by including additional smooth mass components and allowing values of the BCG parameters to vary independently from those of the other cluster members. These different models are tested for our gold sample of clusters, whereas in the silver sample we do not have enough constraints.…”

“…For the smooth mass components (i.e., dark matter, intracluster light and hot gas), we used a pseudo-isothermal elliptical mass distribution (PIEMD, Kassiola & Kovner 1993), that has been shown to describe well such component in previous studies (e.g. Grillo et al 2015;Caminha et al 2017b). A PIEMD profile is characterised by a total of six parameters: the central velocity dispersion (σ v ) and core radius (r core ); the orientation angle (θ) and ellipticity (ε); and the position of the centre (x, y).…”

SZ contribution to characterize the shape of galaxy cluster haloes

“…This is one of the largest spectroscopic sample of cluster members available to date for a z > 0.1 cluster, and indeed at all redshifts. With the aforementioned VLT/MUSE observations, a large number of new multiply lensed images have been identified and used to build a high-precision lensing model ( [3]). The combination of all these independent methods has led to the most accurate ever determination of the total gravitating mass for an individual cluster over the radial range 5-5000 kpc (corresponding to about 0-2.5 virial radii; see Fig.…”

“…2). Its 17.7 arcsec angular resolution will give three independent beams within radial scales of 1' and thus bridge the gap between the ACA and Bolocam data, while covering the GNFW model scale radius ([12]) at 51±2 arcsec determined from strong lensing ( [3]). The joint analysis of the SZ effect from 3.3 arcseconds (ALMA) to 5 arcminutes (IRAM/NIKA2, Bolocam) will enable us to make it comparable to our X-ray data, allowing e.g.…”

“…Our joint analysis will offer a unique opportunity to obtain an accurate and precise estimate of the baryonic and dark mass distributions, together with their 3D shapes, assessing at high accuracy any systematic bias affecting the measurements of the hydrostatic mass once it is compared with the dynamical and lensing masses from the inner core out to 2 Mpc. [3]. They will be used to assess the robustness of the hydrostatic mass measurement.…”