Issue |
A&A
Volume 669, January 2023
|
|
---|---|---|
Article Number | L15 | |
Number of page(s) | 7 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/202245481 | |
Published online | 18 January 2023 |
Letter to the Editor
Atomic oxygen abundance toward Sagittarius B2⋆,⋆⋆
1
Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Drove Drive, Pasadena, CA 91109, USA
e-mail: Dariusz.C.Lis@jpl.nasa.gov
2
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
3
I. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, 50937 Köln, Germany
Received:
16
November
2022
Accepted:
23
December
2022
A substantial fraction of oxygen in diffuse clouds is unaccounted for by observations and is postulated to be in an unknown refractory form, referred to as unidentified depleted oxygen (UDO), which, depending on the local gas density, may contribute up to 50% of the total oxygen content. Previous Infrared Space Observatory (ISO) observations suggest that a significant fraction of oxygen in even denser, translucent clouds may be in atomic form. We have analyzed velocity-resolved archival SOFIA observations of the 63 μm fine-structure [O I] transition toward the high-mass star-forming region Sgr B2(M) in the Central Molecular Zone. The foreground spiral-arm clouds as well as the extended Sgr B2 envelope between the Sun and the background dust continuum source produce multiple [O I] absorption components, spectrally separated in velocity space. The gas-phase atomic oxygen column density in foreground clouds toward Sgr B2 is well correlated with the total hydrogen column density, with an average atomic oxygen abundance of (2.51 ± 0.69) × 10−4 with respect to hydrogen nuclei. This value is in good agreement with the earlier ISO measurements on the same line of sight, and is about 35% lower than the total interstellar medium oxygen abundance in the low-density warm gas, as measured in the UV. We find no evidence that a significant fraction of the oxygen on the line of sight toward Sagittarius B2 is in the form of UDO.
Key words: astrochemistry / ISM: abundances / ISM: atoms / ISM: molecules / ISM: lines and bands / ISM: clouds
Tables with the data used for Figs. 2 and B.3 are only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/669/L15
© The Authors 2023
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