This is the astro-ph blog of the Theoretical Modelling of Cosmic Structures group (TMoX) at the Max-Planck-Institute for Extraterrestrial Physics. We are an independent Max-Planck Research Group focusing on the various aspects in the formation and evolution of galaxies. Part of our focus is on the formation and evolution of early-type galaxies, super-massive black holes, the formation of the first structures in the universe and the enrichment history of the Universe. We are theoreticians using analytic modelling as well as numerical simulations in our work.

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31 May 2012

Galactic star formation and accretion histories from matching galaxies to dark matter haloes

Authors: Moster et al (2012)
Paper: here

The authors perform a 'multi-epoch abundance matching' model (MEAM) for 0<z<4. Subhaloes are taken from the Millennium I and II simulations, and satellites are forced to have the same stellar mass as centrals at the time of infall (i.e. self-consistent treatment, but with no SF for satellites). The results are then combined with merger trees extracted from the dark matter simulations to predict the average assembly histories of galaxies, separated into star formation within the galaxies (in-situ) and accretion of stars (ex-situ).

Results: The peak star formation efficiency decreases with redshift from 23% at z=0 to 9% at z=4 while the corresponding halo mass increases from 10^11.8 Msun to 10^12.5 Msun. The star formation rate of central galaxies peaks at a redshift which depends on halo mass; for massive haloes this peak is at early cosmic times while for low-mass galaxies the peak has not been reached yet. In haloes similar to that of the Milky-Way about half of the central stellar mass is assembled after z=0.7. In low-mass haloes, the accretion of satellites contributes little to the assembly of their central galaxies, while in massive haloes more than half of the central stellar mass is formed ex-situ with significant accretion of satellites at z<2.

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