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.

The CosmologyCake blog is dedicated to the discussion of research papers and current developments. We will regularly post interesting papers and comment on them. Feel free to leave your comments as well. We encourage authors of discussed papers to post replies if they wish to. Our aim is to provide a platform to discuss recent astro-ph papers within a wider audience. Please feel free to send papers you would like to be discussed to us at

31 May 2012

The sizes, masses and specific star-formation rates of massive galaxies

Authors: McLure et al, 2012
Text: here

The authors in this paper present results from recent observations based on a mass complete (M > 6*10^10 M_sun) high redshift (z~1.4) sample of galaxies. The focus of the paper is on the sizes of these galaxies and their correlation with other physical properties such as specific star formation (sSFR,) stellar ages and morphology of the galaxies. The paper shows convincingly that galaxies at z~1.4 are more compact then the local counterparts by a factor 1.6 - 2.4 depending on their sSFR. Based on simple toy models they then go on to claim, that the size-evolution is dominated by minor mergers.

A very interesting result of this work is that morphology and sSFR do not correlate strongly. The authors conclude based on this that two separate process must be responsible for the morphological transformation and the shutting down of the SFR.

The latter conclusion is still somewhat debated in the community.

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