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The Large Dispersion and Scattering of FRB 20190520B Are Dominated by the Host Galaxy

Koch Ocker, Stella and Cordes, James M. and Chatterjee, Shami and Niu, Chen-Hui and Li, Di and McKee, James W. and Law, Casey J. and Tsai, Chao-Wei and Anna-Thomas, Reshma and Yao, Ju-Mei and Cruces, Marilyn (2022) The Large Dispersion and Scattering of FRB 20190520B Are Dominated by the Host Galaxy. Astrophysical Journal, 931 (2). Art. No. 87. ISSN 0004-637X. doi:10.3847/1538-4357/ac6504. https://resolver.caltech.edu/CaltechAUTHORS:20220531-843979000

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Abstract

The repeating fast radio burst FRB 20190520B is localized to a galaxy at z = 0.241, much closer than expected given its dispersion measure DM = 1205 ± 4 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 τ(1.41 GHz) = 10.9 ± 1.5 ms, which is attributed to the host galaxy, and a mean scintillation bandwidth Δν_d(1.41 GHz) = 0.21 ± 0.01 MHz, which is attributed to the Milky Way. Balmer line measurements for the host imply an Hα emission measure (galaxy frame) EMₛ = 620 pc cm⁻⁶ × (T/10⁴ K)^(0.9), implying DM_(Hα) of order the value inferred from the FRB DM budget, DMₕ = 1121_(−138)^(+89) pc cm⁻³ for plasma temperatures greater than the typical value 10⁴ K. Combining τ and DMₕ yields a nominal constraint on the scattering amplification from the host galaxy F^~G =1.5_(-0.3}){(0.8) pc² km^(-1/3), 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 τ arises from the host galaxy and Δν_d from the Milky Way, the implied distance between the FRB source and dominant scattering material is ≲100 pc. The host galaxy scattering and DM contributions support a novel technique for estimating FRB redshifts using the τ–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.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/ac6504DOIArticle
https://arxiv.org/abs/2202.13458arXivDiscussion Paper
ORCID:
AuthorORCID
Koch Ocker, Stella0000-0002-4941-5333
Cordes, James M.0000-0002-4049-1882
Chatterjee, Shami0000-0002-2878-1502
Niu, Chen-Hui0000-0001-6651-7799
Li, Di0000-0003-3010-7661
McKee, James W.0000-0002-2885-8485
Law, Casey J.0000-0002-4119-9963
Tsai, Chao-Wei0000-0002-9390-9672
Anna-Thomas, Reshma0000-0001-8057-0633
Yao, Ju-Mei0000-0002-4997-045X
Cruces, Marilyn0000-0001-6804-6513
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2022 February 1; revised 2022 April 5; accepted 2022 April 5; published 2022 May 27. The authors thank the anonymous referee and R. Main for comments that improved this work. S.K.O., J.M.C., and S.C. acknowledge support from the National Science Foundation (AAG 1815242) and are members of the NANOGrav Physics Frontiers Center, which is supported by NSF award PHY-2020265. C.H.N. is supported by the FAST Fellowship and D.L. acknowledges support from the National Natural Science Foundation of China (NSFC) Program Nos. 11988101 and 11725313. C.W.T. acknowledges support from NSFC No. 11973051. J.W.M. is a CITA Postdoctoral Fellow supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), [funding reference #CITA 490888-16]. C.J.L. acknowledges support from the National Science Foundation under Grant No. 2022546. R.A.T. acknowledges support from NSF grant AAG-1714897.
Group:Owens Valley Radio Observatory (OVRO)
Funders:
Funding AgencyGrant Number
NSFAST-1815242
NSFPHY-2020265
FAST FellowshipUNSPECIFIED
National Natural Science Foundation of China11988101
National Natural Science Foundation of China11725313
National Natural Science Foundation of China11973051
Canadian Institute for Theoretical AstrophysicsUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)CITA 490888-16
NSFAST-2022546
NSFAST-1714897
Subject Keywords:Radio bursts; Radio transient sources; Interstellar medium; Intergalactic medium; Interstellar scattering
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Radio bursts (1339); Radio transient sources (2008); Interstellar medium (847); Intergalactic medium (813); Interstellar scattering (854)
DOI:10.3847/1538-4357/ac6504
Record Number:CaltechAUTHORS:20220531-843979000
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20220531-843979000
Official Citation:Stella Koch Ocker et al 2022 ApJ 931 87
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114971
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:01 Jun 2022 18:36
Last Modified:01 Jun 2022 18:36

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