Thesis Defense 4/24/2023 — Presented By Calvin Leung

Monday April 24, 2023 10:00 am

April 24th, Tuesday @ 10:00 am –  Marlar Lounge, 37-252/37-272
Committee: Kiyoshi Masui (Chair), Jackie Hewitt, David Kaiser

Localization and Lensing of Fast Radio Bursts using CHIME/FRB and its VLBI Outriggers

Every two minutes, a luminous, millisecond-duration flash of radio light arrives at Earth from outside the Milky Way. These fast radio bursts (FRBs) are elusive: they last just a millisecond, and the vast majority are never detected again. FRBs have drawn significant interest because of their potential as a probe of black holes and cosmic structure, as well as their connection to magnetars: a rare class of neutron stars which produce the strongest magnetic fields in the Universe. Observationally, however, because FRBs are so fleeting, the field is grappling with much simpler questions: How do magnetars emit FRBs? From what galaxies (and redshifts) do FRBs originate? Pinpointing FRBs to their host galaxies using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is perhaps the single most promising path towards uncovering the mystery of FRBs. CHIME’s wide field of view allows FRBs to be detected at an unprecedented rate of about 1000 per year: 10× more than other telescopes combined. However, CHIME lacks the resolution to pinpoint its bursts. Very-long baseline interferometry (VLBI) is a solution which uses widely-separated telescopes to achieve high angular resolution, but this technique traditionally has a narrow field of view, which until now has limited it to following up the small fraction of sources which repeat. In this thesis, I develop key technologies to overcoming a major obstacle in the field: combining wide-field observations for FRB detection with high angular resolution for localization in one instrument. As a demonstration, I successfully pinpoint a one-off FRB with sub-arcsecond precision at the time of detection, setting the stage for CHIME Outriggers: three dedicated telescopes which will enhance CHIME’s angular resolution to sub-arcsecond scales over CHIME’s entire field of view. In addition, I develop a new way to use FRBs as probes of primordial black hole dark matter on sub-solar mass scales. By exploiting multi-path interference in gravitational lensing, I develop a novel method to search for interferometrically-lensed FRBs. We find that some FRBs exhibit plasma lensing (scintillation), which we attribute to the Milky Way’s interstellar medium, and use our null search to place new constraints on extragalactic primordial black holes as dark matter.

via Zoom

Best of luck to Calvin!


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