Max Planck Institute for Astronomy - Annual Report 2005

78 III. Scientific Work
tion rate of a galaxy depend much more strongly on halo
mass than on luminosity. The well-known fact that more
luminous galaxies consist of a larger fraction of early types
therefore merely reflects that more luminous galaxies, on
average, reside in more massive haloes. Note also that the
fraction of intermediate type galaxies is independent of halo
mass and independent of luminosity. This argues against
these intermediates being edge-on disk galaxies, since if
this were the case their occupation statistics would mimic
those of the late-types.
Conclusions and Future Prospects
With the Sloan Digital Sky Survey nearing its completion,
and various high-redshift galaxy surveys well underway,
the future is bright. Our research group will continue
to explore the galaxy-dark matter connection using
the various approaches discussed above, but now applied
to these new observational surveys. Our ultimate goal is
to obtain a detailed picture of how galaxies with different
properties are distributed over halos of different masses
at different redshifts. We will also investigate whether
galaxy properties depend on other halo properties, such
as their large scale environment. All this information
holds important clues regarding galaxy formation, and
we will strive to combine our methodology with galaxy
formation models in order to further our understanding
of the various physical processes involved. Last but not
least, as discussed, our CLF formalism allows a detailed
and accurate description of galaxy bias, thus allowing
us to use the observed galaxy distribution to constrain
cosmological parameters.
(Frank C. van den Bosch, in collaboration with
colleagues from the Partner Group of the MPA at
Shanghai Astronomical Observatory,
the University of Massachussets,
and the University of Zürich)