Kavli Affiliate: Kiyoshi W. Masui
| First 5 Authors: Kaitlyn Shin, Calvin Leung, Sunil Simha, Bridget C. Andersen, Emmanuel Fonseca
| Summary:
Fast radio bursts (FRBs) are unique probes of extragalactic ionized baryonic
structure as each signal, through its burst properties, holds information about
the ionized matter it encounters along its sightline. FRB 20200723B is a burst
with a scattering timescale of $tau_mathrm{400,MHz} >$1 second at 400 MHz
and a dispersion measure of DM $sim$ 244 pc cm$^{-3}$. Observed across the
entire CHIME/FRB frequency band, it is the single-component burst with the
largest scattering timescale yet observed by CHIME/FRB. The combination of its
high scattering timescale and relatively low dispersion measure present an
uncommon opportunity to use FRB 20200723B to explore the properties of the
cosmic web it traversed. With an $sim$arcminute-scale localization region, we
find the most likely host galaxy is NGC 4602 (with PATH probability
$P(O|x)=0.985$), which resides $sim$30 Mpc away within a sheet filamentary
structure on the outskirts of the Virgo Cluster. We place an upper limit on the
average free electron density of this filamentary structure of $langle n_e
rangle < 4.6^{+9.6}_{-2.0} times 10^{-5}$ cm$^{-3}$, broadly consistent with
expectations from cosmological simulations. We investigate whether the source
of scattering lies within the same galaxy as the FRB, or at a farther distance
from an intervening structure along the line of sight. Comparing with Milky Way
pulsar observations, we suggest the scattering may originate from within the
host galaxy of FRB 20200723B.
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