Astron. Astrophys. Suppl. Ser. 136, 269-284

A survey of the ISM in early-type galaxies

II. The dust

F. Ferrari¹ - M.G. Pastoriza¹ - F. Macchetto^2,3 - N. Caon⁴

1 - Instituto de Física, UFRGS, Porto Alegre, Brazil
2 - Space Telescope Science Institute
3 - On assignment from the Space Science Department of ESA
4 - Instituto de Astrofísica de Canarias, Tenerife, Spain

Received May 11, 1998; accepted January 4, 1999

Abstract:

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 A_V and A_R extinction maps. We have found typical A_V values of 0.026 and A_R of 0.023 and have derived (V-R) values in the range 0.49-0.68. The A_V 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 $L_{\mathrm{B}}$ luminosities. Finally, we investigate the possible mechanisms responsible for the dust emission.

Key words: galaxies: elliptical and lenticular -- galaxies: ISM -- dust extinction -- surveys