Minor merger-induced cold fronts in Abell 2142 and RXJ1720.1+2638

TL;DR

This study provides evidence that minor mergers can induce cold fronts in galaxy clusters, demonstrated through detailed spectroscopic analysis of Abell 2142 and RXJ1720.1+2638, linking substructure to cold front formation.

Contribution

It offers new observational evidence connecting minor merger substructures with cold front formation in seemingly relaxed galaxy clusters.

Findings

Substructures detected via optical spectroscopy in both clusters.

Group-scale substructures likely caused cold fronts.

Cold fronts are consistent with minor merger activity.

Abstract

We present evidence for the existence of substructure in the "relaxed appearing" cold front clusters Abell 2142 and RXJ1720.1+2638. The detection of these substructures was made possible by comprehensive multi-object optical spectroscopy obtained with the Hectospec and DEep Imaging Multi-Object Spectrograph instruments on the 6.5m MMT and 10m Keck II telescope, respectively. These observations produced 956 and 400 spectroscopically confirmed cluster members within a projected radius of 3Mpc from the centers of Abell 2142 and RXJ1720.1+2638, respectively. The substructure manifests itself as local peaks in the spatial distribution of member galaxies and also as regions of localized velocity substructure. For both Abell 2142 and RXJ1720.1+2638, we identify group-scale substructures which, when considering the morphology of the cold fronts and the time since pericentric passage of a perturber estimated from the cold front radii, could plausibly have perturbed the cluster cores and generated the cold fronts observed in Chandra images. The results presented here are consistent with cold fronts being the result of merger activity and with cold fronts in relaxed appearing clusters being due to minor merger activity.