CLASH-VLT: The mass, velocity-anisotropy, and pseudo-phase-space density profiles of thez= 0.44 galaxy cluster MACS J1206.2-0847

Abstract

Aims. We constrain the mass, velocity-anisotropy, and pseudo-phase-space density profiles of the z = 0.44 CLASH cluster MACS J1206.2-0847, using the projected phase-space distribution of cluster galaxies in combination with gravitational lensing. Methods. We use an unprecedented data-set of 600 redshifts for cluster members, obtained as part of a VLT/VIMOS large program, to constrain the cluster mass profile over the radial range ∼0-5 Mpc (0-2.5 virial radii) using the MAMPOSSt and Caustic methods. We then add external constraints from our previous gravitational lensing analysis. We invert the Jeans equation to obtain the velocity-anisotropy profiles of cluster members. With the mass-density and velocity-anisotropy profiles we then obtain the first determination of a cluster pseudo-phase-space density profile. Results. The kinematics and lensing determinations of the cluster mass profile are in excellent agreement. This is very well fitted by a NFW model with mass M 200 = (1.4 ± 0.2) × 10 15 M and concentration c 200 = 6 ± 1, only slightly higher than theoretical expectations. Other mass profile models also provide acceptable fits to our data, of (slightly) lower (Burkert, Hernquist, and Softened Isothermal Sphere) or comparable (Einasto) quality than NFW. The velocity anisotropy profiles of the passive and star-forming cluster members are similar, close to isotropic near the center and increasingly radial outside. Passive cluster members follow extremely well the theoretical expectations for the pseudo-phase-space density profile and the relation between the slope of the mass-density profile and the velocity anisotropy. Star-forming cluster members show marginal deviations from theoretical expectations. Conclusions. This is the most accurate determination of a cluster mass profile out to a radius of 5 Mpc, and the only determination of the velocityanisotropy and pseudo-phase-space density profiles of both passive and star-forming galaxies for an individual cluster. These profiles provide constraints on the dynamical history of the cluster and its galaxies. Prospects for extending this analysis to a larger cluster sample are discussed.

Calibration of systematics in constraining modified gravity models with galaxy cluster mass profiles

“…ref. [17]) over the distribution of tracers in our sample of phase spaces; we assume a projected NFW model, obtained by integrating eq. (2.5) along the l.o.s., where the only free parameter is the scale radius r ν of the profile.…”

“…Since galaxies are non relativistic objects (typical velocity dispersion is of the order of ∼ 10 3 km/s c, see e.g. [17]) they perceive only the time-time component of the metric, expressed by the potential Φ. On the other hand, photons, due to the conformal structure of Maxwell equations, are sensitive to both Φ and Ψ.…”

The Projected Dark and Baryonic Ellipsoidal Structure of 20 CLASH Galaxy Clusters*

“…Umetsu et al (2014) employed the color-color (CC) selection method of Medezinski et al (2010) to identify background galaxy populations, typically using the Subaru/ Suprime-Cam BR C z′ photometry where available (for a summary, see Table 1 of Umetsu et al 2014), which spans the full optical wavelength range. The photometric zero points were precisely calibrated to an accuracy of ∼0.01 mag, using the HST photometry of cluster elliptical galaxies and with a set of galaxies having spectroscopic redshifts from the CLASH-VLT large spectroscopic program with VIMOS (e.g., Biviano et al 2013;Annunziatella et al 2014;Rosati et al 2014;Grillo et al 2015;Balestra et al 2016), which obtained thousands of spectroscopic redshifts for cluster members and intervening galaxies along the line of sight, including lensed background galaxies.…”

“…In this work, we employ the robust biweight estimators of Beers et al (1990) for the center location (C BI ) and scale (S BI ) of the marginalized 1D posterior distributions (e.g., Stanford et al 1998;Sereno & Umetsu 2011;Biviano et al 2013). The biweight estimator is insensitive to and stable against outliers, as it assigns higher weight to points that are closer to the center of the distribution (Beers et al 1990).…”

Velocity Segregation and Systematic Biases in Velocity Dispersion Estimates with the SPT-GMOS Spectroscopic Survey

“…Member selection must be treated thoughtfully in order to minimize potential biases in the dispersion estimates that could arise by including, for example, large numbers of interloper galaxies. We apply a two-stage member selection process designed to emulate the "peak+gap" procedure that has been used in many previous studies Biviano et al 2013;Girardi et al 2015;Barsanti et al 2016). This procedure relies on a first stage selection that takes place solely in line-of-sight velocity space, identifying velocity distributions associated with clusters as over-densities in the available radial velocity catalogs.…”