An Unbiased Search for Molecular Clouds in the Southern Galactic Warp
An Unbiased Search for Molecular Clouds in the Southern Galactic Warp
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DOI：
10.1093/pasj/57.6.917
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发表时间：
2005-10
影响因子：
2.3
通讯作者：
M. Nakagawa;T. Onishi;A. Mizuno;Y. Fukui
中科院分区：
文献类型：
--
作者：
M. Nakagawa;T. Onishi;A. Mizuno;Y. Fukui
We made an unbiased search for molecular clouds in the Galactic Warp. This survey, covering an area of 56 square degrees at l = 252 ◦ to 266 ◦ and b = −5 ◦ to −1 ◦ , revealed 70 molecular clouds, while only 6 clouds were previously known in this sector at R 14.5kpc. The mass of the clouds is in a range from 7.8 ×10 2 Mto 8.4 ×10 4 M� , significantly less than the most massive giant molecular clouds in the inner disk, ∼10 6 M� , while the cloud mass spectrum characterized by a power law is basically similar to other parts of the Galaxy. The X factor, N(H2)/ T( 12 CO) dV, derived from the molecular clouds in the Warp, is estimated to be 3.5(±1.8)-times larger than that in the inner disk. The total molecular mass in the Warp is estimated to be 7.3 ×10 5 M� , and the total mass in the far-outer Galaxy (R 14.5kpc) can be estimated to be 2 ×10 7 M� . The spatial correlation between the CO and H I distribution appears to be fairly good, and the mass of the molecular gas is about 1% of that of the atomic gas in the far-outer Galaxy. This ratio is similar to that in the interarm, but is ten-times smaller than those of the spiral arms. Only 6 of the 70 Warp clouds show signs of star formation at the IRAS sensitivity, and the star-formation efficiency for high-mass stars in the Warp is found to be smaller than those in other molecular clouds in the Galaxy.
