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Small Region, Big Impact: Highly Anisotropic Lyman-continuum Escape from a Compact Starburst Region with Extreme Physical Properties

Kim, Keunho J.; Bayliss, Matthew B.; Rigby, Jane R.; Gladders, Michael D.; Chisholm, John; Sharon, Keren; Dahle, Håkon; Rivera-Thorsen, T. Emil; Florian, Michael K.; Khullar, Gourav; Mahler, Guillaume; Mainali, Ramesh; Napier, Kate A.; Navarre, Alexander; Owens, M. Riley; Roberson, Joshua

Small Region, Big Impact: Highly Anisotropic Lyman-continuum Escape from a Compact Starburst Region with Extreme Physical Properties Thumbnail


Authors

Keunho J. Kim

Matthew B. Bayliss

Jane R. Rigby

Michael D. Gladders

John Chisholm

Keren Sharon

Håkon Dahle

T. Emil Rivera-Thorsen

Michael K. Florian

Gourav Khullar

Ramesh Mainali

Kate A. Napier

Alexander Navarre

M. Riley Owens

Joshua Roberson



Abstract

Extreme, young stellar populations are considered to be the primary contributor to cosmic reionization. How the Lyman continuum (LyC) escapes these galaxies remains highly elusive, and it is challenging to observe this process in actual LyC emitters without resolving the relevant physical scales. We investigate the Sunburst Arc, a strongly lensed LyC emitter at z = 2.37 that reveals an exceptionally small-scale (tens of parsecs) region of high LyC escape. The small (<100 pc) LyC-leaking region has extreme properties: a very blue UV slope (β = −2.9 ± 0.1), a high ionization state ([O iii] λ5007/[O ii] λ3727 = 11 ± 3 and [O iii] λ5007/Hβ = 6.8 ± 0.4), strong oxygen emission (EW([O iii]) = 1095 ± 40 Å), and a high Lyα escape fraction (0.3 ± 0.03), none of which are found in nonleaking regions of the galaxy. The leaking region's UV slope is consistent with approximately "pure" stellar light that is minimally contaminated by the surrounding nebular continuum emission or extinguished by dust. These results suggest a highly anisotropic LyC escape process such that LyC is produced and escapes from a small, extreme starburst region where the stellar feedback from an ionizing star cluster creates one or more "pencil-beam" channels in the surrounding gas through which LyC can directly escape. Such anisotropic escape processes imply that random sight-line effects drive the significant scatters between measurements of galaxy properties and LyC escape fraction, and that strong lensing is a critical tool for resolving the processes that regulate the ionizing budget of galaxies for reionization.

Citation

Kim, K. J., Bayliss, M. B., Rigby, J. R., Gladders, M. D., Chisholm, J., Sharon, K., …Roberson, J. (2023). Small Region, Big Impact: Highly Anisotropic Lyman-continuum Escape from a Compact Starburst Region with Extreme Physical Properties. Astrophysical Journal Letters, 955(1), Article L17. https://doi.org/10.3847/2041-8213/acf0c5

Journal Article Type Article
Acceptance Date Aug 15, 2023
Online Publication Date Sep 27, 2023
Publication Date Sep 1, 2023
Deposit Date Feb 26, 2024
Publicly Available Date Feb 26, 2024
Journal The Astrophysical Journal Letters
Print ISSN 2041-8205
Electronic ISSN 2041-8213
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 955
Issue 1
Article Number L17
DOI https://doi.org/10.3847/2041-8213/acf0c5
Keywords Space and Planetary Science; Astronomy and Astrophysics
Public URL https://durham-repository.worktribe.com/output/2287258
Additional Information Article Title: Small Region, Big Impact: Highly Anisotropic Lyman-continuum Escape from a Compact Starburst Region with Extreme Physical Properties; Journal Title: The Astrophysical Journal Letters; Article Type: paper; Copyright Information: © 2023. The Author(s). Published by the American Astronomical Society.; Date Received: 2023-05-21; Date Accepted: 2023-08-15; Online publication date: 2023-09-27

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