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 2 2 early-type luminous galaxies, selected from the RC3 Catalog. A large frac tion (75%) of the observed galaxies show significant amounts of dust. The m orphology and size of the dust distribution of the observed galaxies follow s 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 value s together with an assumption of the dust grain size and composition enable us to estimate the dust masses. We have studied the correlations between t he mass of dust and the H alpha, IR and L-B luminosities. Finally, we inves tigate the possible mechanisms responsible for the dust emission.