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arXiv · 1511.01940

Large-scale CO (J=4-3) Mapping toward the Orion-A Giant Molecular Cloud

Shun Ishii·Masumichi Seta·Makoto Nagai·Yusuke Miyamoto·Naomasa Nakai·Taketo Nagasaki·Hitoshi Arai·Hiroaki Imada·Naoki Miyagawa·Hiroyuki Maezawa·Hideki Maehashi·Leonardo Bronfman·Ricardo Finger
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Abstract

We have mapped the Orion-A Giant Molecular Cloud in the CO (J=4-3) line with the Tsukuba 30-cm submillimeter telescope.The map covered a 7.125 deg^2 area with a 9' resolution, including main components of the cloud such as Orion Nebula, OMC-2/3, and L1641-N. The most intense emission was detected toward the Orion KL region. The integrated intensity ratio between CO (J=4-3) and CO (J=1-0) was derived using data from the Columbia-Univ. de Chile CO survey, which was carried out with a comparable angular resolution. The ratio was r_{4-3/1-0} ~ 0.2 in the southern region of the cloud and 0.4-0.8 at star forming regions. We found a trend that the ratio shows higher value at edges of the cloud. In particular the ratio at the north-eastern edge of the cloud at (l, b) = (208.375 deg, -19.0 deg) shows the specific highest value of 1.1. The physical condition of the molecular gas in the cloud was estimated by non-LTE calculation. The result indicates that the kinetic temperature has a gradient from north (Tkin=80 K) to south (20 K). The estimation shows that the gas associated with the edge of the cloud is warm (Tkin~60 K), dense (n_{H_2}~10^4 cm^{-3}), and optically thin, which may be explained by heating and sweeping of interstellar materials from OB clusters.

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Shun Ishii, Masumichi Seta, Makoto Nagai, Yusuke Miyamoto, Naomasa Nakai, Taketo Nagasaki, Hitoshi Arai, Hiroaki Imada, Naoki Miyagawa, Hiroyuki Maezawa, Hideki Maehashi, Leonardo Bronfman, Ricardo Finger. 2015-11-05. Large-scale CO (J=4-3) Mapping toward the Orion-A Giant Molecular Cloud. https://doi.org/10.1093/pasj%2Fpsv116

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