Deciphering the Origins of FRBs Using Local Universe CHIME/FRB Discoveries

Fast radio bursts (FRBs) are one of astronomy’s greatest mysteries. These millisecond-duration radio pulses are powerful enough to be observed from distant galaxies. Althoughover a thousand FRBs have been discovered to date, their origin remains a hotly debatedtopic primarily due to the dearth of FRBs with known hosts. A promising method to narrowdown FRB origins is by identifying their hosts and/or multi-wavelength counterparts. Moreimportantly, with milliarcsecond localization precision, it is possible to study the FRBs’ lo-cal environment in the host, which is crucial to test if the FRB progenitors constitute an oldor young stellar population. However, due to the limited sensitivity of telescopes operat-ing in the optical and X-ray wavebands, multi-wavelength follow-up is most promising forlocal Universe sources (z < 0.1).The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a transit radiotelescope operating in the frequency range of 400-800 MHz. Due to its enormous field-of-view (∼220 sq.deg.), large collecting area (8000 sq.m.), broad frequency coverage (400-800 MHz), and highly sophisticated software back-end, CHIME has revolutionized theFRB field by discovering the majority of all known FRB sources to date. For some of theCHIME FRBs, we acquire raw voltage data that can facilitate localization to sub-arcminuteor a few arcminutes precision. This angular resolution can be sufficient to identify hostgalaxies of local Universe FRBs due to the low chance association probability.In this thesis, we discuss the pipeline that facilitates the identification of plausible hostgalaxies of the local Universe CHIME FRBs. Using this pipeline, we identified host galax-ies of the two closest extragalactic FRBs discovered to date, FRB 20200120E and FRB20181030A. FRB 20200120E has the dispersion measure of 87.82 pc cm−3 , which is the lowest recorded from an FRB to date. The FRB appears on the outskirts of M81 (projectedoffset ∼ 20 kpc), a spiral galaxy at a distance of 3.6 Mpc, but well inside its extended HIand thick disks. We search for prompt X-ray counterparts in Swift/BAT and Fermi/GBMdata, and for two of the FRB 20200120E bursts, we rule out coincident SGR 1806−20-likeX-ray bursts. For FRB 20181030A, we identify NGC 3252, a star-forming spiral galaxylocated at the distance of ≈ 20 Mpc, as its most likely host. With the discovery of thissecond-closest extragalactic FRB, we argue that a population of young millisecond mag-netars alone cannot explain the observed volumetric rate of repeating FRBs.In addition to these two closest extragalactic FRBs, we perform follow-up studies oftwo nearby repeating CHIME FRBs, FRB 20180814A and 20190303A. For FRB 20180814A,the second repeating FRB discovered in 2018, we find an early-type lenticular galaxy at thespectroscopic redshift of 0.068 as its plausible host. If this galaxy is not the FRB host, weargue that the host of FRB 20180814A will be the faintest host known to date. For FRB20190303A, we identify a merging pair of star-forming spiral galaxies at the spectroscopicredshift of 0.064 as its most likely host. These two vastly different host associations clearlyhighlight the complex nature of FRB host and progenitor populations

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