The Double Galaxy Cluster A2465. III. X-Ray and Weak-lensing Observations^∗

Abstract

We report Chandra X-ray observations and optical weak-lensing measurements from Subaru/SuprimeCam images of the double galaxy cluster Abell 2465 (z = 0.245). The X-ray brightness data are fit to a β-model to obtain the radial gas density profiles of the northeast (NE) and southwest (SW) sub-components, which are seen to differ in structure. We determine core radii, central temperatures, the gas masses within r 500c , and the total masses for the broader NE and sharper SW components assuming hydrostatic equilibrium. The central entropy of the NE clump is about two times higher than the SW. Along with its structural properties, this suggests that it has undergone merging on its own. The weak-lensing analysis gives virial masses for each substructure, which compare well with earlier dynamical results. The derived outer mass contours of the SW sub-component from weak lensing are more irregular and extended than those of the NE. Although there is a weak enhancement and small offsets between X-ray gas and mass centers from weak lensing, the lack of large amounts of gas between the two sub-clusters indicates that Abell 2465 is in a pre-merger state. A dynamical model that is consistent with the observed cluster data, based on the FLASH program and the radial infall model, is constructed, where the subclusters currently separated by ∼ 1.2 Mpc are approaching each other at ∼ 2000 km s −1 and will meet in ∼ 0.4 Gyr.

Cluster–galaxy weak lensing

“…For sufficiently massive clusters at low redshift, deep weak-lensing observations allow us to constrain the halo shape on an individual cluster basis, by forwardmodeling the observed two-dimensional shear (or convergence) field with elliptical lens models (Oguri et al 2010;Okabe et al 2011;Watanabe et al 2011;Umetsu et al 2012;Medezinski et al 2013Medezinski et al , 2016Wegner et al 2017). This towdimensional fitting approach is flexible and can be readily generalized to include multiple halo components (see the discussion in Sect.…”

Source selection for cluster weak lensing measurements in the Hyper Suprime-Cam survey

“…The color-color (CC) selection method has been extensively presented and explored in Medezinski et al (2010) and used in the literature (Medezinski et al 2011(Medezinski et al , 2013(Medezinski et al , 2016Oguri et al 2012;Umetsu et al 2012Umetsu et al , 2014Umetsu et al , 2015Formicola et al 2016;Wegner et al 2017;Monteiro-Oliveira et al 2017). It is based on conservatively rejecting galaxies in areas of color space suspected as having a large fraction of cluster or foreground galaxies.…”

Simulating the Arrival of the Southern Substructure in the Galaxy Cluster Abell 1758

“…Shock heating of the gas is a naturally expected phenomenon in a premerging system, commonly predicted in simulations (e.g., Takizawa 1999), and also observed in many premerging clusters (e.g., Paterno-Mahler et al 2014;Akamatsu et al 2016Akamatsu et al , 2017. If the projected separation between the two clusters is larger than the sum of their individual virial radii, temperature enhancements are generally not observed (e.g., Andrade-Santos et al 2015;Wegner et al 2017). In the case of A1758, it is conceivable that the intervening gas, having been previously perturbed by the internal A1758N collision, may be more prone to heating than it would otherwise be if A1758N were a relaxed cluster.…”