Seminar by Aklant Bhowmick, University of Virginia
Deciphering the first "seeds" of supermassive black holes (BH) is a key science goal for current facilities such as the James Webb Space Telescope (JWST) and upcoming facilities like the Laser Interferometer Space Antenna (LISA) gravitational wave observatory. Most popular candidates include "light" seeds as Population III stellar remnants (~102 solar masses), "medium-weighted" seeds as merger remnants of stellar and BH collisions in dense nuclear star clusters (~103-104 solar masses), and "heavy seeds" formed out of direct collapse of gas (~104-106 solar masses). However, most cosmological simulations employ very simplistic seeding prescriptions due to their inability to explicitly resolve the seed masses and the formation processes. I will talk about our new suite of BRAHMA cosmological simulations that implement a novel set of physically motivated BH seeding prescriptions that rely on a wide range of gas properties, including high gas density, low gas metallicity, strong Lyman Werner radiation, low gas angular momentum, and rich halo environment. To model low mass seeds in larger simulation volumes, we have developed a novel stochastic seed model that can faithfully represent the descendants of seeds that are ~10-100 times below the simulation resolution. Using our new seed models, we have carried out one of the largest systematic studies for quantifying the impact of BH seeding, on BH populations across cosmic time. I'll talk about the key signatures of our seed models in a wide range of BH observables such as the BH merger rates detectable by LISA, high-z stellar mass vs BH mass relations probed by JWST, and the local BH occupation fractions in dwarf galaxies.
Host: Zoltan Haiman