MUSTANG High Angular Resolution Sunyaev-Zel'dovich Effect Imaging of Sub-Structure in Four Galaxy Clusters

TL;DR

This study uses high-resolution Sunyaev-Zel'dovich Effect imaging to reveal sub-structures and shock features in four galaxy clusters, providing insights into their merger dynamics and intra-cluster medium properties.

Contribution

The paper presents the first high-resolution SZE images of multiple galaxy clusters, detecting sub-structures and shock fronts, and demonstrating the technique's potential to study cluster dynamics.

Findings

Detection of a weak shock-front in MACS0744+3927 with Mach number ~1.2

Confirmation of shock-heated gas in RXJ1347-1145 due to recent merger

Identification of sub-structure and elongation in CL1226+3332 related to merger activity

Abstract

We present 10" to 18" images of four massive clusters of galaxies through the Sunyaev-Zel'dovich Effect (SZE). These measurements, made at 90~GHz with the MUSTANG receiver on the Green Bank Telescope (GBT), reveal pressure sub-structure to the intra-cluster medium (ICM) in three of the four systems. We identify the likely presence of a previously unknown weak shock-front in MACS0744+3927. By fitting the Rankine-Hugoniot density jump conditions in a complementary SZE/X-ray analysis, we infer a Mach number of M = 1.2^{+0.2}_{-0.2} and a shock-velocity of 1827^{+267}_{-195}~km/s. In RXJ1347-1145, we present a new reduction of previously reported data and confirm the presence of a south-east SZE enhancement with a significance of 13.9 sigma when smoothed to 18" resolution. This too is likely caused by shock-heated gas produced in a recent merger. In our highest redshift system, CL1226+3332, we detect sub-structure at a peak significance of 4.6 sigma in the form of a ridge oriented orthogonally to the vector connecting the main mass peak and a sub-clump revealed by weak lensing. We also conclude that the gas distribution is elongated in a south-west direction, consistent with a previously proposed merger scenario. The SZE image of the cool core cluster Abell 1835 is, in contrast, consistent with azimuthally symmetric signal only. This pilot study demonstrates the potential of high-resolution SZE images to complement X-ray data and probe the dynamics of galaxy clusters