Abell 1201: a Minor merger at second core passage

TL;DR

This paper analyzes the merging dynamics of Abell 1201, revealing a second core passage of a subcluster through detailed X-ray observations, cold front structures, and a proposed merger scenario.

Contribution

It provides new insights into the merger stage of Abell 1201, identifying the offset core as a remnant of a subcluster in its second pericenter passage.

Findings

Detection of a gas tail stripped from the offset core.

Identification of cold fronts indicating sloshing caused by merger.

Evidence supporting a second core passage scenario.

Abstract

We present an analysis of the structures and dynamics of the merging cluster Abell~1201, which has two sloshing cold fronts around a cooling core, and an offset gas core approximately 500kpc northwest of the center. New Chandra and XMM-Newton data reveal a region of enhanced brightness east of the offset core, with breaks in surface brightness along its boundary to the north and east. This is interpreted as a tail of gas stripped from the offset core. Gas in the offset core and the tail is distinguished from other gas at the same distance from the cluster center chiefly by having higher density, hence lower entropy. In addition, the offset core shows marginally lower temperature and metallicity than the surrounding area. The metallicity in the cool core is high and there is an abrupt drop in metallicity across the southern cold front. We interpret the observed properties of the system, including the placement of the cold fronts, the offset core and its tail in terms of a simple merger scenario. The offset core is the remnant of a merging subcluster, which first passed pericenter southeast of the center of the primary cluster and is now close to its second pericenter passage, moving at ~1000 km/s. Sloshing excited by the merger gave rise to the two cold fronts and the disposition of the cold fronts reveals that we view the merger from close to the plane of the orbit of the offset core.