1303.3586 (Qi Guo et al.)

The limits of subhalo abundance matching    [PDF]

Qi Guo, Simon White

Subhalo abundance matching (SHAM) inserts galaxies into dark matter only simulations of the growth of cosmic structure in a way that requires minimal assumptions about galaxy formation. A galaxy is placed at the potential minimum of each distinct self-bound subhalo with a luminosity which is a monotonically increasing function of the maximum mass (or circular velocity) attained over the subhalo's earlier history. Galaxy and subhalo properties are linked by matching model and observed luminosity functions. Simulated structures can then be compared in detail with observation, for example, through galaxy correlation statistics, group catalogues, or galaxy-galaxy lensing. Physically meaningful results require the abundance and clustering of suhalos to be unaffected by numerical resolution. Here we use the Millennium and Millennium-II simulations with subhalos defined using the SUBFIND algorithm to explore the limitations imposed by this requirement. Correlation statistics on scales between 200 kpc and 2 Mpc converge to within 20% only for subhalos with maximum past masses corresponding to 1000 simulation particles or more. This is substantially above the mass limit to which results are quoted in recent SHAM analyses. Detailed galaxy formation simulations based on semi-analytic techniques converge to much lower mass, because they follow galaxies even after their associated subhalos have been tidally disrupted.

View original: http://arxiv.org/abs/1303.3586