A survey of the ISM in early-type galaxies - II. The dust

We present results of a CCD optical imaging survey of the dust content in 22 early-type luminous galaxies, selected from the RC3 Catalog. A large fraction (75%) of the observed galaxies show significant amounts of dust. The morphology and size of the dust distribution of the observed galaxies follows very closely that of the ionized gas. For each galaxy, we have used broad band V and R filters imaging to build colour maps and determine the Av and AR extinction maps. We have found typical Av values of 0.026 and A(R) of 0.023 and have derived (V - R) values in the range 0.49 - 0.68. The Av values together with an assumption of the dust grain size and composition enable us to estimate the dust masses. We have studied the correlations between the mass of dust and the H alpha, IR and L-B luminosities. Finally, we investigate the possible mechanisms responsible for the dust emission.