Special MSI Seminar

Investigating Local Environments of Fast Radio Bursts

Alexandra Mannings

UC Santa Cruz

Fast Radio Bursts (FRBs) are mili-second duration pulses of radio emission, usually from extragalactic sources. A well-received progenitor theory is that which implicates magnetars, but bursts show a diverse range of properties including, fluence, tendency to repeat, etc., suggesting a broader diversity of progenitor channels. We study the local environments of a set of 9 bursts to create a more complete picture of the possible production mechanisms - taking a closer look at the stellar populations, estimated progenitor age, density of star-formation and more at the FRB location. In this presentation, I will describe methods we use to characterize the local environments including the use of high-resolution, deep imaging from Hubble Space Telescope (HST) and, later on, the search for correlation between local and galactic characteristics and burst properties such as the rotation measure (RM). We are able to show that FRBs occur at moderate galactocentric offsets (median host-normalized offset being 1.4 effective radii), and they occur in regions of moderate brightness relative to the rest of the galaxy light. These point us away from progenitors that require long delay times, or prompt emission from massive star death. Investigation into rotation measure of a subset of bursts, allows us to look at the power of probing galactic magnetic fields with FRBs, as we determine the host galaxies to have relatively low to moderate magnetic field strengths (compared to the widely accepted range of 5-15 microGauss range for massive, star-forming galaxies). We also search for correlations from this limited sample, and find weak correlations between rotation measure and galaxy properties. Upcoming experiments like CRACO will provide a breadth of FRBs with high-precision localizations, rotation measures, and imaging follow-up to support further investigation into FRB local environments. Uncovering information about stellar populations, magnetic field properties - and how these track burst properties - can teach us more about this unique transient event and more broadly, galaxy formation and evolution.