Simulations of Lyα Absorption from Low Surface Brightness Galaxies

Using simulations of the low redshift galaxy population based upon galaxy observations, it is shown (Linder 1998) that the majority of Ly$\alpha$ absorbers at low redshift could arise in low surface brightness (LSB) galaxies. The contribution to absorption from LSB galaxies is large for any galaxy surface brightness distribution which is currently supported by observations. Ly\alpha absorbers should become powerful tools for studying the properties and evolution of galaxies, but first it will be necessary to establish observationally the nature of the Ly\alpha absorbers at low redshift. Further simulations, in which the absorbing galaxy population is 'observed' with some selection criteria, are used to explore how easily possible it is for an observer to test for a scenario in which LSB galaxies give rise to most of the Ly$\alpha$ absorbers. It is shown that absorption arising in LSB galaxies is often likely to be attributed to high surface brightness galaxies at larger impact parameters from the quasar line of sight.