Astrophysics Brown Bag Lunch Talk 9/12/2022: Speakers: Casey Lam (Berkeley) And Uddipan Banik (Yale)

Monday September 12, 2022 12:00 pm

In Person in Marlar and/or Virtual Brown Bag Lunch 
Monday September 12, 2022 at 12:00 Link Below
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Presentation in Marlar 37-252/37-272 for those wishing to attend in person

Casey Lam/Berkeley at 12:05 (Virtual)

Uncovering the Galactic Black Hole Population with Gravitational Microlensing

Abstract:  A substantial fraction of the Milky Way’s black holes (BHs) are expected to be isolated, but until recently they have eluded detection. I will present the analysis of 5 archival isolated BH candidates identified via gravitational microlensing. One of the candidates (OGLE-2011-BLG-0462/MOA-2011-BLG-191) is likely a neutron star or BH. The full sample of 5 candidates is compared to theoretical expectations on the number of BHs in the Milky Way detectable via microlensing, and is consistent with 100 million Galactic BHs.

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Uddipan Banik/Yale at 12:30 pm (in person)

Pushing the frontiers of gravitational encounters and collisionless dynamics

Abstract:  Relaxation/equilibration of perturbed galaxies and cold dark matter halos is typically a collisionless process. I will present a perturbative formalism to compute the response of perturbed (by bars, satellite impacts, etc.) disk galaxies that phase-mixes away, giving rise to phase-spirals akin to those observed by Gaia. I will also present novel analytical techniques (perturbative and non-perturbative) to model the secular evolution (dynamical friction) of a massive perturber orbiting in a spherical host galaxy/halo, explaining the origin of secular phenomena such as core-stalling and dynamical buoyancy observed in N-body simulations of cored galaxies but unexplained in the standard Chandrasekhar framework. This has far-reaching astrophysical implications, e.g., potential choking of supermassive black hole mergers and merger-driven nuclear object formation in cored host galaxies.​


Event Contact

Josh Borrow