Revisiting the low-luminosity galaxy population of the NGC 5846 group with SDSS

Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, 1180 Vienna, Austria e-mail: eigenthaler@astro.univie.ac.at

Received: 22 September 2008
Accepted: 26 November 2009

Abstract

Context. Low-luminosity galaxies are known to outnumber the bright galaxy population in poor groups and clusters of galaxies. Yet, the investigation of low-luminosity galaxy populations outside the Local Group remains rare and the dependence on different group environments is still poorly understood. Previous investigations have uncovered the photometric scaling relations of early-type dwarfs and a strong dependence of morphology with environment.

Aims. The present study aims to analyse the photometric and spectroscopic properties of the low-luminosity galaxy population in the nearby, well-evolved and early-type dominated NGC 5846 group of galaxies. It is the third most massive aggregate of early-type galaxies after the Virgo and Fornax clusters in the local universe. Photometric scaling relations and the distribution of morphological types as well as the characteristics of emission-line galaxies are investigated.

Methods. Spectroscopically selected low-luminosity group members from the Sloan Digital Sky Survey with cz < 3000 km s^-1 within a radius of 2° = 0.91 Mpc around NGC 5846 are analysed. Surface brightness profiles of early-type galaxies are fit by a Sérsic model . Star formation rates, oxygen abundances, and emission characteristics are determined for emission-line galaxies.

Results. Seven new group members showing no entry in previous catalogues are identified in the outer (>1.33°) parts of the system. Several photometric scaling relations for dEs as well as the morphology-density relation for dwarf galaxies are reproduced. The correlation between host and satellite morphologies in poor groups of galaxies is also confirmed. Nucleated dwarfs are found to be located in the vicinity to the brightest ellipticals in the group. Only two faint galaxies exhibit fine structure. Emission-line dwarfs show no interaction-induced activity.