Probing the large-scale clustering of fast radio bursts with CHIME/FRB

Abstract

Explaining the nature of extragalactic fast radio bursts (FRBs) has puzzled astrophysicists since 2007. In this thesis, we introduce the CHIME/FRB instrument, an FRB search engine that could solve this puzzle through FRB population studies. We explore CHIME/FRB science results, with an emphasis on the FRB-galaxy correlation. First, we formulate a framework for characterizing FRBs (e.g. by constraining their redshift and host dispersion measure distributions) through angular cross-correlations with large-scale structure. Using this machinery we model, forecast and simulate the FRB-galaxy correlation for two distinct FRB models. Then, we apply this technique to real data, using the first CHIME/FRB catalog along with five photometric redshift catalogs of galaxies. Computing the FRB-galaxy cross power spectrum, we find a statistically significant (p-value ~ 10⁻⁴, accounting for look-elsewhere factors) cross-correlation between CHIME FRBs and galaxies in the redshift range 0.3 ≲ z ≲ 􏰂0.5. The strength and angular scale of the cross-correlation are consistent with an order-one fraction of CHIME FRBs being in this redshift range, and in the same dark matter halos as the survey galaxies. Finally, we find statistical evidence for a subpopulation of FRBs with large host dispersion measure (host DM ~ 400 pc/cm³) at z ~ 0.4. We show that such large host DMs could be explained by a small population of FRBs near the centers (r ≲ 100 kpc) of large (M ~ 10¹⁴ M⊙) halos.