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

20 January 2012

The cosmic web and the orientation of angular momenta

This paper (link) uses a dark matter only simulation to see if a collapsed, virialized halo remembers the cosmic web out of which it formed. The new work in this paper uses the eigenvalues of the velocity shear tensor to determine if a halo is in a knot, filament, sheet, or void. Then, they measure the angle between the halo angular momentum and the eigenvectors, and the subhalo orbital angular momentum and the eigenvectors. Interestingly, the internal angular momentum correlates with the eigenvectors in sheets and filaments, implying that even virialized halos retain memory of the initial conditions. The orbital angular momentum in substructures is aligned in knots, filaments, and sheets, implying that halo accretion is not isotropic. This work has impact in understanding the spatial distribution of satellites around host galaxies, as is seen in the Milky Way and the SDSS sample.

Which galaxy property is the best indicator of its host dark matter halo properties?

This paper (link) discusses an interesting new observational trend: It is found that the clustering of massive galaxies depends more strongly on the central velocity dispersion (s) than on stellar mass (m). This fact is emphasized by measuring w_p for subsamples of a given s (or m) at various bins in m (or s). The authors claim that this observational evidence supports the idea that the halo mass is more tightly related to s, than to m. In addition, the paper includes results that show the clustering dependence on surface density, color, and dynamical mass estimates.

13 January 2012

Disruption of a Proto-Planetary Disk by the Black Hole at the Milky Way Center

This (link) is a very interesting paper trying to explain the properties of the gas cloud close to Sgr A* using back of the envelope calculations. Though the model will not be the final word in the study of this gas cloud, it provides interesting prediction, especially on its density evolution, without the use of any numerical simulations. It will be interesting to see how it will hold up with respect to detailed numerical simulations that are underway or already run (e.g.