Friday, 20 November 2009

The evolving stellar-to-halo mass ratio

In this paper (not really new one; it was posted to astro-ph in
March), Moster et al. use (something like) an abundance-matching
technique to match galaxies to halos. The paper focuses mostly on
z=0, but they also show results for higher redshifts, where they use
stellar mass functions from Drory and from Fontana.

This figure shows the average stellar mass as a function of halo mass
at different redshifts. I've drawn a line that shows the what a
constant ratio would look like. The highest ratio (which means the
highest efficiency for putting baryons in stars) for the z=0 curve
appears at a stellar mass of log(M)~10.5, and increases with
redshift. Another thing to notice is that the curves evolve strongly
at lower masses, and cross at higher masses. This means that, at
lower masses, galaxies grow in mass much faster than their halos. But
at higher masses halos grow faster than galaxies.

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