Properties of dust extinction in NGC 2076

Abstract

Early-type galaxies with large-scale dust are suitable objects to investigate the propeties of dust extinction in extragalactic environments because the underlying galaxies have fairly smooth distribution of the starlight. Total dust content and the physical propeties of dust grains may be a function of time and galaxy environment, and thus detailed studies of dust properties may provide important clues about the nature, origin and subsequent evolution of dust in galaxies. In this paper we present multiband CCD surface photometry of NGC 2076, a lenticular, having a very prominent dust lane running parallel to the apparent major axis of the galaxy. The main objective is to investigate the wavelength dependence of the dust extinction and to estimate dust mass from optical as well as FIR data. The extinction curve is very similar to our Galaxy, having a value of 2.7 for Rv, defined as the ratio of total visual extinction Av to selective extinction between B and V, E(B-V). The smaller value of Rv for NGC 2076 than the canonical value for our Galaxy Rv = 3.1, implies that the size of dust grains responsible for extinction in NGC 2076 is less than that in our Galaxy. The estimate of dust mass from optical colour excess, total extinction as well as from FIR flux are found to be of the same order and are therefore consistent with one another.