  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.

Astrophysics