Diffuse stellar emission in X-ray luminous galaxy clusters at z~0.3 I. Is the diffuse optical light boosted and rejuvenated in merging clusters?

TL;DR

This study investigates diffuse stellar emission around brightest cluster galaxies in three X-ray luminous galaxy clusters at z~0.3, revealing its extent, color properties, and potential links to cluster merging processes and intracluster light.

Contribution

It provides the first detailed analysis of diffuse stellar emission in these clusters, highlighting differences related to dynamical state and merging activity.

Findings

Diffuse stellar emission detected around seven BCGs up to 100 kpc.

Diffuse light in merging clusters shows bluer colors than BCG centers.

Diffuse light distribution follows the ICM in relaxed clusters.

Abstract

[Abridged] We searched for diffuse stellar emission around BCGs in three of the most X-ray luminous clusters found at z~0.3 in the REFLEX cluster survey and observed with XMM-Newton. These systems (RXCJ0014.3-3022, RXCJ0232.2-4420, and RXCJ2308.3-0211) are in different dynamical states, as witnessed by their X-ray morphology and optical appearence (e.g. multiplicity of BCGs). [Abridged] Diffuse stellar emission is robustly detected down to a surface brightness of 26 R-mag/arcsec^2 (observed frame) around a total of seven BCGs, extending up to galactocentric distances of ~100 kpc. In particular, it surrounds a pair of BCGs in RXCJ0232.2-4420, while it bridges two BCGs associated with the minor subcomponent of the merging cluster RXCJ0014.3-3022. The diffuse light detected at the greatest distances from the BCGs of the rather regular clusters RXCJ0232.2-4420 and RXCJ2308.3-0211 follows the ICM distribution. Its B-R colour is consistent with the colours measured within the BCG effective radii. The diffuse light around the two pairs of BCGs in RXCJ0014.3-3022 exhibits bluer colours than the BCG central regions by up to 0.5 mag. If the contribution of the intracluster light (ICL) to the detected diffuse light around BCGs is not negligible, ICL and BCGs have similar stellar populations in relatively relaxed clusters. Merging on a cluster scale eventually adds gravitational stresses to BCGs and other galaxies in subcluster cores. This event may affect the properties of the diffuse stellar emission around BCGs. Shredding of star-forming, low-metallicity dwarf galaxies is favoured as the cause of the bluer B-R colours of the diffuse stellar component around the two pairs of BCGs in the merging cluster RXCJ0014.3-3022.