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The observed impact of galaxy halo gas on fast radio bursts

Connor, Liam and Ravi, Vikram (2022) The observed impact of galaxy halo gas on fast radio bursts. Nature Astronomy, 6 (9). pp. 1035-1042. ISSN 2397-3366. doi:10.1038/s41550-022-01719-7. (In Press)

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Image (JPEG) (Extended Data Fig. 1: A simulation of CHIME/FRB DMs to compare the statistical power and appropriateness of three tests: Student’s one-sided t-test, our jackknife test, and the Kolmogorov-Smirnov (KS) test) - Supplemental Material
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Image (JPEG) (Extended Data Fig. 2: Predicted DM excesses for CHIME/FRB galaxy intersections assuming isolated galaxy halos) - Supplemental Material
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Image (JPEG) (Extended Data Fig. 3: Predicted DM excesses for 26 FRBs intersecting halos of different masses) - Supplemental Material
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Galaxies and groups of galaxies exist in dark-matter haloes filled with diffuse gas. The diffuse gas represents up to 80% of the mass in baryonic matter within the haloes, but is difficult to detect because of its low density (particle number densities of ≲10⁻⁴ cm⁻³) and high temperature (mostly >10⁶ K). Here we analyse the impact of diffuse gas associated with nearby galaxies using the dispersion measures (DMs) of extragalactic fast radio bursts (FRBs). FRB DMs provide direct measurements of the total ionized-gas contents along their sightlines. Out of a sample of 474 distant FRBs from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB Catalog 1 (ref. 3), we identify a subset of events that probably intersect the dark-matter haloes of galaxies in the local Universe (<40 Mpc). The mean DM of the galaxy-intersecting FRBs is larger than that of the non-intersecting FRBs with a probability >0.99 and the excess DM is >90 pc cm⁻³ with >95% confidence. The excess is larger than expected for the diffuse gas surrounding isolated galaxies, but may be explained by additional contributions from gas surrounding galaxy groups, including from the Local Group. This result demonstrates the predicted ability of FRBs to be used as sensitive, model-independent measures of the diffuse gas contents of dark-matter haloes.

Item Type:Article
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URLURL TypeDescription ReadCube access ItemCHIME/FRB Catalog 1 ItemGWGC Itemfrb python package ItemDiscussion Paper
Connor, Liam0000-0002-7587-6352
Ravi, Vikram0000-0002-7252-5485
Additional Information:© 2022 Springer Nature Limited. Received 13 August 2021. Accepted 18 May 2022. Published 04 July 2022. We thank C. Hummels, W. Lu, J. M. Shull and the Caltech FRB group for helpful discussions. We also thank C. Leung, K. Masui and M. Bhardwaj for valuable comments on the manuscript. This research was partially supported by the National Science Foundation under grant number AST-1836018. Contributions. V.R. conceived of searching only nearby foreground galaxies for FRB–halo intersections. L.C. developed the methods for cross-matching the catalogues, statistically testing the DM distributions and analysing the DM excess that are reported in Figs. 1–3 and the results. V.R. modelled the halo DM contribution shown in Extended Data Fig. 3. L.C led the writing of the manuscript in close collaboration with V.R. Data availability. All the data used in these analyses are publicly available. CHIME/FRB Catalog 1 can be found at The GWGC can be downloaded at Code availability. This research made use of the open-source hmf, NFW, CHIME/FRB’s cfod package and frb ( python packages. All custom code used in our analysis is available from the corresponding author upon request. The authors declare no competing interests. Peer review information. Nature Astronomy thanks Masoud Rafiei-Ravandi and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
Group:Astronomy Department, Owens Valley Radio Observatory (OVRO)
Funding AgencyGrant Number
Issue or Number:9
Record Number:CaltechAUTHORS:20220707-978170000
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Official Citation:Connor, L., Ravi, V. The observed impact of galaxy halo gas on fast radio bursts. Nat Astron (2022).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115421
Deposited By: George Porter
Deposited On:08 Jul 2022 21:46
Last Modified:15 Feb 2023 19:20

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