Suzaku Observations of AWM 7 Cluster of Galaxies: Temperature, Abundance and Bulk Motions

TL;DR

This study used Suzaku to observe the AWM 7 galaxy cluster, revealing temperature and abundance profiles, chemical enrichment differences, and constraints on bulk motions, indicating recent gas infall rather than rotation.

Contribution

First detailed Suzaku measurements of temperature, abundance, and bulk motions in AWM 7, highlighting unique chemical enrichment and gas dynamics.

Findings

Temperature decreases slightly with radius.

Abundance ratios suggest different supernova enrichment processes.

No significant bulk motion detected, indicating recent gas infall.

Abstract

We carried out 3 observations of the cluster of galaxies AWM 7, for the central region and 20'-east and 20'-west offset regions, with Suzaku. Temperature and abundance profiles are measured out to 27'~ 570 /h_70 kpc, which corresponded to ~0.35 r_180. The temperature of the intra-cluster medium (ICM) slightly decreases from 3.8 keV at the center to 3.4 keV in ~0.35 r_180 region, indicating a flatter profile than those in other nearby clusters. Abundance ratio of Si to Fe is almost constant in our observation, while Mg to Fe ratio increases with radius from the cluster center. O to Fe ratio in the west region shows increase with radius, while that in the east region is almost flat, though the errors are relatively large. These features suggest that the enrichment process is significantly different between products of type II supernovae (O and Mg) and those by type Ia supernovae (Si and Fe). We also examined positional shift of the central energy of He-like Fe-Ka line, in search of possible rotation of the ICM. The 90% upper limit for the line-of-sight velocity difference was derived to be v ~ 2000 km/s, suggesting that the ellipticity of AWM 7 is rather caused by a recent directional infall of the gas along the large-scale filament.