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Session 10 - Spiral Galaxies.
Display session, Monday, June 10
Great Hall,
lore the hypothesis that the majority of the Ly\alpha absorption at low redshift is explained by outer galaxy disks, once dwarfs and low surface brightness (LSB) galaxies are included. Numerous extended, gas-rich LSB galaxies have been discovered recently, and they must make some contribution to the Ly\alpha absorption. Evidence is also building for the existence of a substantial population of low luminosity dwarf galaxies, and many observations of dwarfs show extended LSB envelopes. Outer galaxy disks may be both extended and highly ionized, so that they could provide a large cross section for Ly\alpha forest absorption. A sample of galaxies is simulated using parameter distributions based on observations of galaxies at various levels of surface brightness. The number density of galaxies is constrained by comparing the sample to absorber counts at low redshift, and the shape of the low-redshift neutral hydrogen column density distribution is predicted for forest absorbers
