A multiwavelength study of the galaxy content and environmental effects in the dense group of galaxies around IC 65

Abstract

We have carried out surface photometry of four bright known members and a number of new possible LSB companions of the IC 65 (LGG 16) group of galaxies. The purpose of the present study is twofold: (a) a search for new LSB dwarf members and measuring of their global photometric characteristics, and (b) a search for possible effects of mutual interactions on the morphology and photometric characteristics of luminous and faint group members. This study is based on our BRI CCD observations performed with the 1.23 m and 2.2 m telescopes at Calar Alto, which were supplemented by the deep gri frames obtained from the DSS 2, and the NIR JHK frames from the 2MASS database. In addition, we have used the HI imaging data from literature and the results of new pilot HI observations of selected dwarf-galaxy candidates made by W. Huchtmeier with the Effelsberg 100 m radiotelescope. We have found four new probable LSB dwarf members of the group, two of which have been marginally detected in HI. The isophotal analysis in optical wavelengths revealed the presence of minor disturbances in the outer isophotes of some bright regular member galaxies. The HI emission appears generally more disturbed, compared to the emission in the optical passbands. The new dwarf companion candidates generally contain blue star-forming regions. The drift of optical isophotes together with the warping of HI isophotes outside the optical image of regular galaxies, as well as evidence for the enhanced star-forming activity in fragile dwarf galaxies indicate that this dense group of at least 8 late type galaxies is gravitationally bound and mutually interacting. (abridged)