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Session 83 - Elliptical Galaxies.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center

[83.01] A Survey of the ISM in Elliptical Galaxies. I. The Ionized Gas

N. Caon, F. Macchetto (STScI -- on assignment from the Astrophysics Division, ESA), M. G. Pastoriza (IF-UFRGS, Porto Alegre, Brazil)

We present the results of an optical imaging survey of 73 luminous early-type galaxies directed to study the properties of their interstellar medium. We have found that a large fraction of E (72%) and S0 (85%) galaxies in our sample contain a measurable amount of ionized gas. The gas morphology appears to be rather smooth; however 12% of the sample galaxies show a complex and extended (as much as 10 kpc from the nucleus) filamentary structure.

We find a significant correlation between H\alpha+[NII] and X-ray luminosities; the distribution of datapoints and upper limits suggests that the presence of warm gas is always associated with the presence of a hot gaseous halo, while there exist strong X-ray emitters with no H\alpha+[NII] emission. Similar, although less clear, characteristics are displayed by the L_H\alpha+[NII]-L_IR 12\mu m correlation.

There is also a strong correlation between the blue-luminosity within the line-emitting region and the H\alpha+[NII] luminosity. This correlation indicates that the heating and ionization of the gas by ultraviolet photons from post-AGB stars is a very plausible and attractive mechanism to explain the observed H\alpha+[NII] luminosity.

Program listing for Wednesday