Large-scale CO (J=4–3) mapping toward the Orion-A giant molecular cloud
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We have mapped the Orion-A giant molecular cloud in the CO(J=4–3) line with the Tsukuba 30cm submillimeter telescope. The map covered a 7.125 deg2 area with a 9 resolution, including main components of the cloud such as the 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–Universidad de Chile CO survey, which was carried out with a comparable angular resolution. The ratio was r4−3/1−0 ∼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 values at the edges of the cloud. In particular, the ratio at the northeastern edge of the cloud at (l, b) ≈ (208. ◦ 375, −19. ◦ 0) shows the 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 (nH2∼ 104 cm−3), and optically thin, which may be explained by heating and sweeping of interstellar materials from OB clusters.
Artículo de publicación ISI
Quote ItemPubl. Astron. Soc. Japan (2016) 68 (1), 10 (1–13)
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