Dottorato - PhD thesis
Area Tematica: RSN 1: Galassie e Cosmologia
Referente: Paramita Barai (
Titolo: Growth and Feedback of the First Supermassive Black Holes: Enigma of the Overmassive versus Normal-mass
Decorrenza: 15.10.2025
This PhD thesis aims to investigate the first Supermassive Black Holes (SMBHs) in the early Universe, by performing and analyzing Cosmological Hydrodynamical Simulations. In particular, the goals would be to distinguish between the physical growth modes of the observed overmassive and normal-mass SMBHs; and identify if their feedback signatures are different and could be observable.
Recent James Webb Space Telescope (JWST) observations are revealing SMBHs of masses 10^7-10^8 Msun at redshift z~10-12. This adds to the population of early SMBHs, which are observed to have grown to 10^9 Msun by z=6 in high-z quasars. Some of these first SMBHs are overmassive in their host galaxy (e.g. Maiolino et al. 2024: https://ui.adsabs.harvard.edu/abs/2024A%26A...691A.145M) with respect to the z=0 SMBH-to-stellar mass correlation. At the same time, JWST observations have also detected a population of normal-mass SMBHs at z~4-6 (e.g. Li et al. 2025: https://ui.adsabs.harvard.edu/abs/2025arXiv250205048L), with the SMBH-to stellar mass ratio consistent with the local relation. The existence of such normal SMBHs together with the previous sample of overmassive SMBHs, imply that there might be diverse pathways for SMBH formation in high-redshift galaxies. The exact formation channels of these "normal-mass" and overmassive SMBHs, specifically in terms heavy seeds or super-Eddington accretion onto lighter stellar-mass seeds, have not been identified yet (e.g. Jeon et al. 2025: https://ui.adsabs.harvard.edu/abs/2025arXiv250314703J).
The PhD project involves performing zoom-in cosmological hydrodynamical simulations of high-z galaxies hosting SMBHs (similar to that in Barai et al. 2018: https://ui.adsabs.harvard.edu/abs/2018MNRAS.473.4003B), using the new version of the state-of-the-art SPH code OpenGADGET. The simulations will try to reproduce the overmassive and normal-mass SMBHs, and determine the distinguished physical conditions (e.g. BH seed mass, super-Eddington BH accretion, mergers, thermal/kinetic AGN feedback, environment) required for the formation of each population. The simulation analyses would quantify the feedback of the SMBHs and identify possible outflow signatures.
The project will be carried out under the scientific supervision of Dr. Paramita Barai (email:
The numerical code OpenGADGET to be used for the simulations are being developed by the Trieste-Munich Numerical Cosmology group. The PhD student will be a part of this group, and they will work in collaboration with the other members including Giuseppe Murante (OATs), Luca Tornatore (OATs), Stefano Borgani (University of Trieste) and Klaus Dolag (University of Munich).
