Nobeyama 45 m Cygnus-X CO Survey. I. Photodissociation of Molecules Revealed by the Unbiased Large-scale CN and C18O Maps

M. Yamagishi, A. Nishimura, S. Fujita, T. Takekoshi, M. Matsuo, T. Minamidani, K. Taniguchi, K. Tokuda, Y. Shimajiri

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11 Citations (Scopus)

Abstract

We present an unbiased large-scale (9 deg2) CN (N = 1-0) and C18O (J = 1-0) survey of Cygnus-X conducted with the Nobeyama 45 m Cygnus-X CO survey. CN and C18O are detected in various objects toward the Cygnus-X North and South (e.g., DR17, DR18, DR21, DR22, DR23, and W75N). We find that CN/C18O integrated intensity ratios are systematically different from region to region, and are especially enhanced in DR17 and DR18, which are irradiated by the nearby OB stars. This result suggests that CN/C18O ratios are enhanced via photodissociation reactions. We investigate the relation between the CN/C18O ratio and strength of the UV radiation field. As a result, we find that CN/C18O ratios correlate with the far-UV intensities, G 0. We also find that CN/C18O ratios decrease inside molecular clouds, where the interstellar UV radiation is reduced due to the interstellar dust extinction. We conclude that the CN/C18O ratio is controlled by the UV radiation, and is a good probe of photon-dominated regions.

Original languageEnglish
Article number9
JournalAstrophysical Journal, Supplement Series
Volume235
Issue number1
DOIs
Publication statusPublished - Mar 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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