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Session 124 - Elliptical Galaxies.
Oral session, Saturday, January 10

[124.01] The Interaction Between Late-Stage Stellar Mass Loss and the Hot ISM in Elliptical Galaxies

J. Parriott, J. N. Bregman (U. Michigan)

Stellar mass loss is thought to be the dominant source of hot gas in elliptical galaxies, but calculations have yet to accurately treat the processes by which this mass loss evolves into the hot ambient medium. We examine the fate of the gas shed by red giants and planetary nebulae as these stars move through the hot ambient galactic medium. The evolution of the stellar ejecta is studied with highly accurate two dimensional numerical hydrodynamic calculations, where the code has been parallelized using a portable message passing standard.

The initial shock between the ambient medium and the stellar ejecta serves to push the ejecta into the wake, but does not raise the temperature of the ejecta to the temperature of the ambient gas. Most of the heating of the stellar ejecta occurs in the wake region through a series of shocks that are often related to irregularities in the wake due to vortex motion and to the growth of Kelvin-Helmholtz instabilities. Significant heating of the stellar ejecta occurs on a time-scale of approximately 10^6 yr and a length-scale of 20 pc for the parameters chosen in our simulations. When radiative cooling is included in the calculations, there is a reduction in the efficiency by which the stellar ejecta is heated to the temperature of the ambient gas.

Program listing for Saturday