[N ii] Fine-structure Emission at 122 and 205 μm in a Galaxy at z = 2.6: A Globally Dense Star-forming Interstellar Medium

Doherty, M. J.; Geach, J. E.; Ivison, R. J.; Dye, S.

Abstract

We present new observations with the Atacama Large Millimeter/submillimeter Array of the 122 and 205 μm fine-structure line emission of singly ionized nitrogen in a strongly lensed starburst galaxy at z = 2.6. The 122/205 μm [N ii] line ratio is sensitive to electron density, ne, in the ionized interstellar medium, and we use this to measure n e ≈ 300 cm-3, averaged across the galaxy. This is over an order of magnitude higher than the Milky Way average, comparable to localized Galactic star-forming regions. Combined with observations of the atomic carbon (C i) and carbon monoxide (CO J = 4-3) in the same system, we reveal the conditions in this intensely star-forming system. The majority of the molecular interstellar medium has been driven to high density, and the resultant conflagration of star formation produces a correspondingly dense ionized phase, presumably colocated with myriad H ii regions that litter the gas-rich disk.

Citation

Doherty, M. J., Geach, J. E., Ivison, R. J., & Dye, S. (2020). [N ii] Fine-structure Emission at 122 and 205 μm in a Galaxy at z = 2.6: A Globally Dense Star-forming Interstellar Medium. Astrophysical Journal, 905(2), Article 152. https://doi.org/10.3847/1538-4357/abc5b9

• Journal Article Type: Article
• Acceptance Date: Oct 28, 2020
• Online Publication Date: Dec 23, 2020
• Publication Date: Dec 20, 2020
• Deposit Date: Jan 5, 2021
• Publicly Available Date: Dec 21, 2021
• Journal: The Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 905
• Issue: 2
• Article Number: 152
• DOI: https://doi.org/10.3847/1538-4357/abc5b9
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://nottingham-repository.worktribe.com/output/5173278
• Publisher URL: https://iopscience.iop.org/article/10.3847/1538-4357/abc5b9
• Additional Information: Journal title: The Astrophysical Journal; Article type: paper; Article title: [N ii] Fine-structure Emission at 122 and 205 μm in a Galaxy at z = 2.6: A Globally Dense Star-forming Interstellar Medium; Copyright information: © 2020. The American Astronomical Society. All rights reserved.; Date received: 2020-08-18; Date accepted: 2020-10-27; Online publication date: 2020-12-23