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J.D. Slavin (SAO)
Gaseous galactic halos have come to our attention because of their optical emission, UV absorption lines, and X-ray emission. A fundamental problem for the understanding of gaseous halos is the nature of energy sources that heat and ionize the warm gas and create the hot gas. Most of the energy sources in galaxies, e.g. hot stars and supernova remnants, are primarily confined to a relatively thin disk (~several hundred pc) in contrast to the thick (~1-several kpc) distribution of gas in halos. The problem with these disk sources is the transport of the energy from the disk to the halo. Several theories have been put forward for energy sources local to the halos, however it is unclear if these sources are capable of supplying the energy needed to maintain the heating and ionization observed. I will discuss theories for the nature of the energy sources for gaseous halos and for the transport of energy from galactic disks to halos.
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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.