# Astro Seminar Series - VIA ZOOM

Wednesday, January 12, 2022 — 11:30 AM EST

Shantanu Basu is an astrophysicist and Professor at Western University. He is known as an expert in studies of the early stages of star formation and protoplanetary disk formation and evolution. Shantanu is one of the originators of the Migrating Embryo Model for protoplanetary disk evolution, which is a unified scenario for angular momentum transport, binary star and giant planet formation, and the formation of ejected freely floating low mass objects. He has recently also contributed to modeling the formation of supermassive black holes at high redshift.

Supermassive Black Holes in the Direct Collapse Scenario

"One of the ideas to explain the existence of supermassive black holes (SMBH) that are in place by $z \sim 7$ is that there was an earlier phase of very rapid accretion onto direct collapse black holes (DCBH) that started their lives with masses $\sim 10^{5}\, \Msun$.  Working in this scenario, we show that the mass function of SMBH after a limited time period of growing formation rate paired with Eddington or super-Eddington accretion can be described as a broken power-law with two characteristic features. These features identify the growth rate and duration of the DCBH era. A lingering concern about the DCBH scenario however is the angular momentum barrier.  Using a set of three-dimensional magnetohydrodynamic (MHD) simulations, we show that the magnetic field efficiently extracts angular momentum from accreting gas and also enhances the coalescence rate of fragments. Almost all the fragments coalesce to the primary star. We conclude that the magnetic field strongly aids the direct collapse scenario of supermassive star formation."

Would you like to join this Zoom seminar?  Please email WCA.

Location
PHY - Physics
Virtual Meeting
200 University Avenue West

Waterloo, ON N2L 3G1

### June 2022

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