A Normal Abundance of Faint Satellites in the Fossil Group NGC 6482

TL;DR

This study reveals that the fossil group NGC 6482 hosts a normal abundance of faint satellite galaxies, with properties similar to those in regular galaxy clusters, based on deep wide-field imaging and detailed analysis.

Contribution

It provides the deepest survey of a fossil group's faint satellites and compares their properties to those of typical galaxy clusters, revealing normal satellite abundance.

Findings

Detected 48 member candidates down to M_R -10.5 mag.

Luminosity function slope is =-1.32b1 0.05.

Color-magnitude relation similar to nearby galaxy clusters.

Abstract

Fossil groups are considered the end product in a galaxy group's evolution -- a massive central galaxy that dominates the luminosity budget of the group, as the outcome of efficient merging between intermediate-luminosity members. Little is however known about the faint satellite systems of fossil groups. Here we present a SUBARU/Suprime-Cam wide-field, deep imaging study in the B- and R-band of the nearest fossil group NGC 6482 (M_{tot}\sim4\times10^{12}M_{\sun}), covering the virial radius out to 310 kpc. We perform detailed completeness estimations and select group member candidates by a combination of automated object detection and visual inspection. A fiducial sample of 48 member candidates down to M_R -10.5 mag is detected, making this study the deepest of a fossil group up to now. We investigate the photometric scaling relations, the colour-magnitude relation, and the luminosity function of our galaxy sample. We find evidence of recent and ongoing merger events among bright group galaxies. The colour-magnitude relation is comparable to that of nearby galaxy clusters, and exhibits significant scatter at the faintest luminosities. The completeness-corrected luminosity function is dominated by early-type dwarfs and is characterized by a faint end slope \alpha=-1.32\pm0.05. We conclude that the NGC 6482 fossil group shows photometric properties consistent with those of regular galaxy clusters and groups, including a normal abundance of faint satellites.