The halo mass function conditioned on density from the Millennium Simulation: insights into missing baryons and galaxy mass functions

Understand

The baryon content of high-density regions in the universe is relevant to two critical unanswered questions: the workings of nurture effects on galaxies and the whereabouts of the missing baryons.

• In this paper, we analyze the distribution of dark matter and semianalytical galaxies in the Millennium Simulation to investigate these problems.
• Applying the same density field reconstruction schemes as used for the overall matter distribution to the matter locked in halos we study the mass contribution of halos to the total mass budget at various background field densities, i.e., the conditional halo mass function.
• In this context, we present a simple fitting formula for the cumulative mass function accurate to ~ 5% for halo masses between 10^{10} and 10^{15}Msol/h.