http://arxiv.org/abs/2203.13846
We study the genesis, environment and growth of supermassive black hole (SMBH) seeds from different formation channels, from PopIII remnants to massive seeds, modeled within the L-Galaxies semi-analytic code. We run the model on the merger trees of the Millennium-II simulation (MR-II), as its high halo-mass resolution (Mvir~10^7 Msun/h) allows to study in a relatively large cosmological volume (Lbox=100 Mpc/h) the evolution of atomic-cooling halos where intermediate-mass and heavy seeds are expected to form. We track the formation of these seeds according to the background and the local variations of the chemical enrichment and the UV-flux produced by star formation. Not being able to resolve the first mini-halos, we account for the formation of PopIII remnants in a sub-grid fashion, using the results of the GQd model. We find that the descendants of light seeds numerically dominate among the population of SMBHs at all masses and z. The much rarer intermediate-mass and heavy seeds form in dense environments where close neighbors provide the required UV illumination. We also include the formation of heavy seeds in the mergers of gas-rich massive galaxies, who are very rare in the MR-II volume. We then track the evolution through gas accretion and mergers of this multi-flavour population of BH seeds down to z=0. Our model produces a population of SMBHs whose statistical properties at z=0 meet current constraints. In the dwarf-mass regime, we predict that the scaling relation between BH and stellar mass is flatter than in the high-mass range. We also find that the BH occupation fraction highly depends on the seeding efficiency. Finally, a fraction of BHs hosted in dwarf galaxies at z=0 never grow since their formation at z>6. This supports the idea that some local low-mass systems might harbor central compact objects which are remnant of high-z BH-formation processes.
D. Spinoso, S. Bonoli, R. Valiante, et. al.
Tue, 29 Mar 22
22/73
Comments: 22 pages, 13 figures, submitted to MNRAS