Properties of Dust in Giant Elliptical Galaxies: The role of the Environment

The properties of dust in giant elliptical galaxies are reviewed, with particular emphasis on the influence of the environment. After normalizing by the optical luminosities, a strong anti-correlation between the masses of dust and hot gas in X-ray bright ellipticals is found. Furthermore, large-scale, regularly-shaped dust lanes (which are symmetric with respect to the galaxy nucleus) are only found to be present in ellipticals with the lowest ratios of the mass of hot gas to the blue luminosity M_hot/L_B < 0.04 in solar units. This can be explained by the short time scale for the destruction of dust grains within hot gas compared to the formation timescale of such dust lanes in early-type galaxies. Dust within ellipticals in loose'' environments (in the field or in loose groups) is typically characterized by small values of R_V = A_V/E(B-V) (i.e., small characteristic grain sizes), and distributed in dust lanes with a smooth, relaxed morphology. On the other hand, dust in ellipticals that are in or near the center of dense groups or clusters is typically much more irregularly distributed, and characterized by R_V values that are close to the Galactic one. I predict that ellipticals containing relaxed’’ dust lanes with typical dust masses of 10E6 - 10E7 solar masses do not contain hot, X-ray-emitting gas.