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

24 March 2011

Recoiling Black Holes in Merging Galaxies...

Link to paper here.
Authors: Laura Blecha, Thomas J. Cox, Abraham Loeb, Lars Hernquist

This proceeding paper present a parameter study of the effect of Gravitational-Wave (GW) recoil of merging supermassive black holes (SMBH). Using a suite of merger SPH simulations, the authors identify systematic trends in the behavior of recoiling BHs. The main results from this study are the following: i) as a function of the escape velocity, kicked BHs may remain confine in gas-rich galaxy merger. ii) recoil events reduce the lifetime of bright AGN, which can still be detectable either as kinematical or spatial offsets. iii) recoiling BHs may be up to 5 time less massive than their stationary counterparts. iv) the displacement of AGN feedback by a recoil causes higher central star formation, hence extending the starburst phase.

An Evolving Stellar Initial Mass Function and the Gamma-ray Burst Redshift Distribution

Link to paper here.
Authors: Wang & Dai

Whether or not the gamma-ray burst rate tracks the overall star formation rate in the universe has been a topic of much interest and debate. In particular, with the ever-growing sample of GRBs at high redshift, it appears that the GRB rate rises faster with redshift than the star formation rate. It has been suggested that this is due to GRB progenitors being of preferentially low metallicity, but some observations show GRBs exploding in metal-rich galaxies so this may not provide a clear explanation for the dicrepancy. In this paper, the authors show that an IMF, such as that suggested by Dave (2010), which becomes more top-heavy at higher redshifts can explain the discrepancy between the star formation rate and the GRB rate.

18 March 2011

Relativistic jet feedback in evolving galaxies
Authors: Alexander Y. Wagner, Geoffrey V. Bicknell

The actual physics of radio-mode AGN feedback is still largely mysterious and so far can be treated in cosmological simulations only by subgrid models. The authors examine the interaction of young radio sources with a fractal two-phase ISM (1 kpc, up to ~105 years) by high resolution simulations with a physical jet implementation. They discuss effects of enhanced or inhibited star formation as well as the momentum and energy budget.

17 March 2011

PCA for Halo properties
Authors: Ramin A. Skibba, Andrea V. Maccio'

The authors study the correlations between the structural parameters of dark matter haloes using Principal Component Analysis (PCA). They find three important components: halo mass, concentration, and halo 'relaxedness'.

10 March 2011

Stellar black holes at the dawn of the universe
Authors: Mirabel, Dijkstra, Laurent, Loeb, Pritchard

The authors propose that feedback from accreting black holes in high-mass X-ray binaries are an important and so-far overlooked source in the process of reionisation. They present an estimate of the total number of ionising photons produced by these sources and discuss some implications for reionisation models.

Disentangling galaxy environment and host halo mass
Authors: Marcel R. Haas (1 and 2), Joop Schaye (1), Akila Jeeson-Daniel

A lot of indicators of galaxy environment used in the (observational) literature are strong indicators of the mass of the halo in which the galaxy resides, the 'internal' environment. These authors give methods to compute a halo mass independent parameter to quantify the 'external' environment of a galaxy.

3 March 2011

On the relative abundance of LiH and LiH+ molecules in the early universe

Authors: Stefano Bovino, Mario Tacconi, Franco A. Gianturco, Daniele Galli, Francesco Palla
full paper:

The authors revisit Li chemistry evolution and perform full
ab-initio computations of reaction rates and cross sections. They find
significant differences with respect to previous works, since, with the
updated data LiH become more aboundant of LiH+ at all redshift.
At z~1, differences with previous works are up to 2 orders of magnitude.