Universität zu Köln

Goldsmith, Paul F., Langer, William D., Seo, Youngmin, Pineda, Jorge, Stutzki, Juergen, Guevara, Christian, Aladro, Rebeca and Justen, Matthias (2021). Interstellar Cloud Conditions Based on 63 mu m [O I] Emission and Absorption in W3. Astrophys. J., 916 (1). BRISTOL: IOP PUBLISHING LTD. ISSN 1538-4357

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Abstract

We investigate the origin of self-absorption in [O I] 63 mu m line emission, which is very clearly seen in approximately half of the 12 Galactic giant molecular cloud (GMC)/H II regions observed. For this study, we observed velocity-resolved spectra of photon-dominated region (PDR) and H II region tracers, the [O I] 63 mu m, [N II] 205 mu m, and CO J = 5-4 and 8-7 lines, with the upGREAT instrument in the 4GREAT configuration on the NASA/DLR Stratospheric Observatory For Infrared Astronomy (SOFIA). To probe the origin of the [O I] absorption and line shape and what they tell us about the physical conditions, we focus on the W3 region, for which we obtained data for eight positions along a line near the H II region W3 A. We derive the foreground column density of low-excitation atomic oxygen to be in the range 2-7 x 10(18) cm(-2). At the position of strongest [O I] emission and greatest absorbing column density, 24% of the oxygen in the PDR is in the form of low-excitation atomic oxygen. We employ the Meudon PDR code to study the chemical and thermal structure of the PDR and to understand the large column density of neutral oxygen throughout the PDR. The reduction in the integrated intensity of the [O I] 63 mu m emission is a factor of similar or equal to 2-4 in directions with strong [O I] emission. The results from our sample, if general, would significantly impact the use of the [O I] 63 mu m line as a tracer of massive star formation and could play a significant role in explaining the 63 mu m [O I] deficit seen in very luminous extragalactic sources.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Goldsmith, Paul F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Langer, William D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Seo, Youngmin UNSPECIFIED UNSPECIFIED UNSPECIFIED Pineda, Jorge UNSPECIFIED UNSPECIFIED UNSPECIFIED Stutzki, Juergen UNSPECIFIED UNSPECIFIED UNSPECIFIED Guevara, Christian UNSPECIFIED UNSPECIFIED UNSPECIFIED Aladro, Rebeca UNSPECIFIED UNSPECIFIED UNSPECIFIED Justen, Matthias UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-585757
DOI:	10.3847/1538-4357/abfb69
Journal or Publication Title:	Astrophys. J.
Volume:	916
Number:	1
Date:	2021
Publisher:	IOP PUBLISHING LTD
Place of Publication:	BRISTOL
ISSN:	1538-4357
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language FAR-INFRARED LINE; FINE-STRUCTURE SPLITTINGS; ATOMIC OXYGEN ABUNDANCE; NARROW SELF-ABSORPTION; GIANT MOLECULAR CLOUD; PERSEUS SPIRAL ARM; PHOTODISSOCIATION REGIONS; PHYSICAL CONDITIONS; C-II; STRUCTURE INTERVALS Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/58575