A normal abundance of faint satellites in the fossil group NGC 6482^⋆,⋆⋆

¹ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany
e-mail: slieder@ari.uni-heidelberg.de
² European Southern Observatory, Av. Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago, Chile
³ NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria BC V9E 2E7, Canada
⁴ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
⁵ National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, 181-8588 Tokyo, Japan

Received: 13 February 2013
Accepted: 3 September 2013

Abstract

A fossil group is considered the end product in a galaxy group’s evolution. It is a massive central galaxy that dominates the luminosity budget of the group, and is the outcome of efficient merging between intermediate-luminosity members. Little is known, however, 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 −bands of the nearest fossil group NGC 6482 (M_tot ~ 4 × 10¹²M_⊙), covering the virial radius out to 310 kpc. We performed detailed completeness estimations and selected 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 to now. We investigate the photometric scaling relations, the color-magnitude relation, and the luminosity function of our galaxy sample. We find evidence of recent and ongoing merger events among bright group galaxies. The color–magnitude relation is comparable to that of nearby galaxy clusters, and it 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 α =  −1.32 ± 0.05. 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.