A two-phase model of galaxy formation: the growth of galaxies and supermassive black holes

I will describe a model for galaxy formation and the growth of supermassive black holes (SMBHs), based on the fact that cold dark matter halos form their gravitational potential wells through a fast phase with rapid change in the potential, and that the high universal baryon fraction makes cooled gas in halos self-gravitating and turbulent before it can form rotation-supported disks. Gas fragmentation produces sub-clouds so dense that cloud-cloud collision and drag on clouds are not significant, producing a dynamically hot system of sub-clouds that form stars and move ballistically to feed the central SMBH.

Active galactic nuclei and supernova feedback is effective only in the fast phase, and the cumulative effects are to regulate star formation and SMBH growth, as well as to reduce the amount of cold gas in halos to allow the formation of globally stable disks. Applied to realistic halo assembly histories, the model can reproduce a number of observations, including correlations among SMBH mass, stellar mass of galaxies and halo mass, the size-mass relation of dynamically hot galaxies, the number densities of galaxies and SMBH, and their evolution over the cosmic time.

Houjun Mo (Univ. Mass)
Yingjie Peng
Thursday, November 23, 2023 - 3:30PM to Thursday, November 23, 2023 - 4:30PM
I am professor of astronomy at University of Massachusetts. My research has been focused on galaxy formation, large-scale structure of the universe, and cosmology. I construct models for the formation of disk galaxies, the formation and structure of dark matter halos, the connection between galaxies and dark matter halos, the structure of gaseous halos, and physical processes related to galaxy formation and evolution. I use galaxies and galaxy systems from observations and from simulations to understand the properties of dark matter halos and the distribution of dark matter in the Universe, as well as to reconstruct the current and initial density fields for the local Universe. I have coauthored a textbook on `Galaxy formation and evolution' which was published by Cambridge University Press. Please refer to my Research and Publications for details of my research interest.