Deep view of the intracluster light in the Coma cluster of galaxies

TL;DR

This study presents the most extensive image of intracluster light in the Coma cluster, revealing its structure, dynamics, and interactions, including a stellar bridge linking the core to NGC 4839, indicating ongoing cluster evolution.

Contribution

It provides the first detailed, large-scale imaging and analysis of intracluster light in Coma, combining deep imaging with extensive spectroscopic data to uncover cluster dynamics and tidal features.

Findings

ICL fractions of ~20% in g and r bands.

Detection of faint tidal features and a stellar bridge.

Evidence of ongoing dynamical interactions in Coma.

Abstract

Detection and study of the intracluster light in rich clusters of galaxies has been a problem of long standing challenge and interest. Using the lowest surface brightness images of the Coma cluster of galaxies in the g and r bands, from the Halos and Environment of Nearby Galaxies (HERON) Coma Cluster Project, we obtained the most extensive image of intracluster light (ICL) in a single cluster to date, spreading over 1.5 Mpc from the cluster core. The unprecedented wealth of spectroscopic data made publicly available by the Dark Energy Spectroscopic Instrument (DESI) Early Data Release, complemented with a compilation from the NASA/IPAC Extragalactic Database and the literature, enabled the identification of 2,157 galaxy members within Coma, from which 42 distinct groups were identified. The synergy between these high-quality data allowed us to: 1) calculate ICL fractions of $19.9\pm0.5$\% and $19.6\pm0.6$\% in the g and r bands, respectively, consistent with a dynamically active cluster, 2) unveil Coma's faintest tidal features, and 3) provide a comprehensive picture of the dynamics and interactions within this complex system. Our findings indicate that the ICL connects several of these groups in a filamentous network, from which we infer the ongoing dynamical processes. In particular, we identified a faint stellar bridge linking the core of Coma with the galaxy NGC 4839, providing compelling evidence that this galaxy has already traversed the central region of the cluster.