The Large Dispersion and Scattering of FRB 20190520B are Dominated by the Host Galaxy. (arXiv:2202.13458v3 [astro-ph.HE] UPDATED)

The Large Dispersion and Scattering of FRB 20190520B are Dominated by the Host Galaxy. (arXiv:2202.13458v3 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Ocker_S/0/1/0/all/0/1">S.K. Ocker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cordes_J/0/1/0/all/0/1">J.M. Cordes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chatterjee_S/0/1/0/all/0/1">S. Chatterjee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Niu_C/0/1/0/all/0/1">C.-H. Niu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_D/0/1/0/all/0/1">D. Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McKee_J/0/1/0/all/0/1">J.W. McKee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Law_C/0/1/0/all/0/1">C.J. Law</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tsai_C/0/1/0/all/0/1">C.-W. Tsai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Anna_Thomas_R/0/1/0/all/0/1">R. Anna-Thomas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yao_J/0/1/0/all/0/1">J.-M. Yao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cruces_M/0/1/0/all/0/1">M. Cruces</a>

The repeating FRB 20190520B is localized to a galaxy at $z=0.241$, much
closer than expected given its dispersion measure $rm DM=1205pm4 pc
cm^{-3}$. Here we assess implications of the large DM and scattering observed
from FRB 20190520B for the host galaxy’s plasma properties. A sample of 75
bursts detected with the Five-hundred-meter Aperture Spherical radio Telescope
shows scattering on two scales: a mean temporal delay $tau(1.41 {rm
GHz})=10.9pm1.5$ ms, which is attributed to the host galaxy, and a mean
scintillation bandwidth $nu_{rm d}(1.41 {rm GHz})=0.21pm0.01$ MHz, which
is attributed to the Milky Way. Balmer line measurements for the host imply an
H$alpha$ emission measure (galaxy frame) $rm EM_s=620$ pc cm$^{-6} times
(T/10^4 {rm K})^{0.9}$, implying $rm DM_{rm Halpha}$ of order the value
inferred from the FRB DM budget, $rm DM_h=1121^{+89}_{-138}$ pc cm$^{-3}$ for
plasma temperatures greater than the typical value $10^4$ K. Combining $tau$
and $rm DM_h$ yields a nominal constraint on the scattering amplification from
the host galaxy $tilde{F} G=1.5^{+0.8}_{-0.3}$ (pc$^2$ km)$^{-1/3}$, where
$tilde{F}$ describes turbulent density fluctuations and $G$ represents the
geometric leverage to scattering that depends on the location of the scattering
material. For a two-screen scattering geometry where $tau$ arises from the
host galaxy and $Delta nu_{rm d}$ from the Milky Way, the implied distance
between the FRB source and dominant scattering material is $lesssim100$ pc.
The host galaxy scattering and DM contributions support a novel technique for
estimating FRB redshifts using the $tau-rm DM$ relation, and are consistent
with previous findings that scattering of localized FRBs is largely dominated
by plasma within host galaxies and the Milky Way.

The repeating FRB 20190520B is localized to a galaxy at $z=0.241$, much
closer than expected given its dispersion measure $rm DM=1205pm4 pc
cm^{-3}$. Here we assess implications of the large DM and scattering observed
from FRB 20190520B for the host galaxy’s plasma properties. A sample of 75
bursts detected with the Five-hundred-meter Aperture Spherical radio Telescope
shows scattering on two scales: a mean temporal delay $tau(1.41 {rm
GHz})=10.9pm1.5$ ms, which is attributed to the host galaxy, and a mean
scintillation bandwidth $nu_{rm d}(1.41 {rm GHz})=0.21pm0.01$ MHz, which
is attributed to the Milky Way. Balmer line measurements for the host imply an
H$alpha$ emission measure (galaxy frame) $rm EM_s=620$ pc cm$^{-6} times
(T/10^4 {rm K})^{0.9}$, implying $rm DM_{rm Halpha}$ of order the value
inferred from the FRB DM budget, $rm DM_h=1121^{+89}_{-138}$ pc cm$^{-3}$ for
plasma temperatures greater than the typical value $10^4$ K. Combining $tau$
and $rm DM_h$ yields a nominal constraint on the scattering amplification from
the host galaxy $tilde{F} G=1.5^{+0.8}_{-0.3}$ (pc$^2$ km)$^{-1/3}$, where
$tilde{F}$ describes turbulent density fluctuations and $G$ represents the
geometric leverage to scattering that depends on the location of the scattering
material. For a two-screen scattering geometry where $tau$ arises from the
host galaxy and $Delta nu_{rm d}$ from the Milky Way, the implied distance
between the FRB source and dominant scattering material is $lesssim100$ pc.
The host galaxy scattering and DM contributions support a novel technique for
estimating FRB redshifts using the $tau-rm DM$ relation, and are consistent
with previous findings that scattering of localized FRBs is largely dominated
by plasma within host galaxies and the Milky Way.

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