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

13 August 2010

Accretion Disks in Active Galactic Nuclei: Gas Supply Driven by Star Formation

Authors: Wang, Yan, Gao, Hu, Li & Zhang
Link to article: arXiv:1007.4060

An analytic model of star formation and gas accretion in the inner ~1pc region surrounding a black hole powering an AGN is presented.  Turbulence generated by supernovae is taken to be responsible for the transport of angular momentum that allows gas to accrete onto the central black hole via a Shakura-Sunyaev accretion disk, which resides between the star forming region and the black hole.  In this model, the black hole accretion rate varies as the star formation rate to the power ~5/7.  The authors further discuss how this model can explain the observed metallicity-luminosity relation of AGN and the formation of nuclear star clusters.


  1. Given that the star formation region is highly turbulent in this model, one might assume that the IMF changes to something that is top-heavy by e.g. gravoturbulent fragmentation (e.g. Larson 2003). Thus, there could be stellar black hole remnants which interact with the surrounding gas and subsequently migrate towards the accretion disk impacting the accretion rate onto the host black hole. If indeed many such remnant black holes would exist, the predictions of this model might need to be modified.

  2. Jarrett said . . .

    A top-heavy IMF would also imply a higher SNe rate and this would lead, in turn, to more turbulent energy injection. If the IMF is sensitive to the turbulence, and vice versa, one might then expect a relationship between the accretion rate and the IMF, in addition to the correlation with the star formation rate.