2DARK天文志

Abstract: We combine N-body simulations of structure growth with physical modelling of
galaxy evolution to investigate whether the shift in cosmological parameters
between the 1-year and 3-year results from the Wilkinson Microwave Anisotropy
Probe affects predictions for the galaxy population. Structure formation is
significantly delayed in the WMAP3 cosmology, because the initial matter
fluctuation amplitude is lower on the relevant scales. The decrease in dark
matter clustering strength is, however, almost entirely offset by an increase
in halo bias, so predictions for galaxy clustering are barely altered. In both
cosmologies several combinations of physical parameters can reproduce observed,
low-redshift galaxy properties; the star formation, supernova feedback and AGN
feedback efficiencies can be played off against each other to give similar
results. Models which fit observed luminosity functions predict projected
2-point correlation functions which scatter by about 10-20 per cent on large
scale and by larger factors on small scale, depending both on cosmology and on
details of galaxy formation. Measurements of the pairwise velocity distribution
prefer the WMAP1 cosmology, but careful treatment of the systematics is needed.
Given current modelling uncertainties, it is not easy to distinguish the WMAP1
and WMAP3 cosmologies on the basis of low-redshift galaxy properties. Model
predictions diverge more dramatically at high redshift. Better observational
data at z>2 will better constrain galaxy formation and perhaps also
cosmological parameters.