Spiral-like structure in nearby clusters of galaxies

TL;DR

This study analyzes deep Chandra X-ray observations of 15 nearby galaxy clusters, revealing spiral-like structures at the cores of 7 clusters, likely caused by off-axis minor mergers, and exploring their connection to radio emissions.

Contribution

It is the first systematic analysis of spiral-like features in cluster cores using high-resolution X-ray data and simulations, linking these structures to minor mergers.

Findings

Spiral-like features detected in 7 out of 15 clusters.

Features are consistent with simulations of off-axis minor mergers.

Possible connection between spiral structures and central radio sources.

Abstract

X-ray data analysis have found that fairly complex structures at cluster centres are more common than expected. Many of these structures have similar morphologies, which exhibit spiral-like substructure. It is not yet well known how these structures formed or are maintained. Understanding the origin of these spiral-like features at the centre of some clusters is the major motivation behind this work. We analyse deep \textit{Chandra} observations of 15 nearby galaxy clusters (0.01 $ < z < $ 0.06), and use X-ray temperature and substructure maps to detect small features at the cores of the clusters. We detect spiral-like features at the centre of 7 clusters: A85, A426, A496, Hydra A cluster, Centaurus, Ophiuchus, and A4059. These patterns are similar to those found in numerical hydrodynamic simulations of cluster mergers with non-zero impact parameter. In some clusters of our sample, a strong radio source also occupies the inner region of the cluster, which indicates a possible connection between the two. Our investigation implies that these spiral-like structures may be caused by off-axis minor mergers. Since these features occur in regions of high density, they may confine radio emission from the central galaxy producing, in some cases, unusual radio morphology.