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The observed impact of galaxy halo gas on fast radio bursts

Presentation #141.05 in the session Intergalactic Medium, QSO Absorption Line Systems — iPoster Session.

Published onJun 29, 2022
The observed impact of galaxy halo gas on fast radio bursts

Galaxies and galaxy groups reside in dark-matter halos filled with diffuse gas. This gas makes up roughly 80% of the mass in baryonic matter associated with galaxies, but is notoriously difficult to detect due to its low density and high temperature. We have analyzed the impact of the diffuse halo gas in nearby galaxies on the dispersion measures (DM) of cosmological fast radio bursts (FRBs). FRB DMs have long been proposed as a probe of the hidden baryonic matter in the Universe as they provide a direct measure of the total ionized gas content along FRB sightlines. Using 474 distant FRBs from the CHIME/FRB Catalog 1, we identify a subset of events that likely intersect the halos of foreground galaxies in the local Universe (<40 Mpc). The mean DM of the galaxy-intersecting FRBs is larger than non-intersecting DMs with high confidence (>99%), and the DM excess is larger than expected. In my talk I will describe this work, and offer an explanation for this high excess. I will also discuss the future implications for FRB cosmology, now that we have demonstrated their predicted ability to measure the diffuse gas contents of dark-matter halos in a model-independent way.

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