High abundance ratio of $^{13}$CO to C$^{18}$O toward photon-dominated regions in the Orion-A giant molecular cloud

Yoshito Shimajiri; Yoshimi Kitamura; Masao Saito; Munetake Momose; Fumitaka Nakamura; Kazuhito Dobashi; Tomomi Shimoikura; Hiroyuki Nishitani; Akifumi Yamabi; Chihomi Hara; Sho Katakura; Takashi Tsukagoshi; Tomohiro Tanaka; Ryohei Kawabe

High abundance ratio of $^{13}$CO to C$^{18}$O toward photon-dominated regions in the Orion-A giant molecular cloud

Yoshito Shimajiri ^{1, 2, 3, *} Yoshimi Kitamura ⁴ Masao Saito ^{5, 2} Munetake Momose ⁶ Fumitaka Nakamura ² Kazuhito Dobashi ⁷ Tomomi Shimoikura ⁷ Hiroyuki Nishitani ^{2, 3} Akifumi Yamabi ⁷ Chihomi Hara ^{2, 8} Sho Katakura ⁷ Takashi Tsukagoshi ⁶ Tomohiro Tanaka ⁹ Ryohei Kawabe ^{2, 5}

* Corresponding author

1 AIM - UMR 7158 - UMR E 9005 - Astrophysique Interprétation Modélisation

2 NAOJ - National Astronomical Observatory of Japan

3 Nobeyama Radio Observatory

4 ISAS - Institute of Space and Astronautical Science

5 ALMA Observatory

6 Ibaraki University

7 Tokyo Gakugei University

8 The University of Tokyo

9 Osaka Prefecture University

Abstract : $Aims$.We derive physical properties such as the optical depths and the column densities of $^{13}$CO to C$^{18}$O to investigate the relationship between the far ultraviolet (FUV) radiation and the abundance ratios between $^{13}$CO to C$^{18}$O. $Methods$. We have carried out wide-field (0.4 deg$^2$) observations with an angular resolution of 25.8''(∼0.05 pc) in $^{13}$CO (J = 1–0) and C$^{18}$O (J = 1–0) toward the Orion-A giant molecular cloud using the Nobeyama 45 m telescope in the on-the-fly mode. $Results$. Overall distributions and velocity structures of the $^{13}$CO to C$^{18}$O emissions are similar to those of the $^{12}$CO (J = 1–0) emission. The optical depths of the $^{13}$CO to C$^{18}$O emission lines are estimated to be 0.05<$\tau_{13}_{CO}$<1.54 and 0.01<$\tau_{C}^{18}$_O$<0.18, respectively. The column densities of the $^{13}$CO and C$^{18}$O emission lines are estimated to be 0.2×10$^{16}$

Keywords : ISM: individual objects: Orion-A ISM: abundances photon-dominated region ISM: clouds

Document type :

Journal articles

Domain :

Physics [physics] / Astrophysics [astro-ph]

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High abundance ratio of $^{13}$CO to C$^{18}$O toward photon-dominated regions in the Orion-A giant molecular cloud

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High abundance ratio of $^{13}$CO to C$^{18}$O toward photon-dominated regions in the Orion-A giant molecular cloud

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