Star Formation Occurs in Dense Gas, but What Does “Dense” Mean?
Evans,Neal J.1,2,3; Kim,Kee-Tae2,4; Wu,Jingwen5; Chao,Zhang5; Heyer,Mark6; Liu,Tie2,7; Nguyen-Lu’o’ng,Quang8,9,10; Kauffmann,Jens11
Source PublicationThe Astrophysical Journal
AbstractAbstract We report results of a project to map HCN and ?emission toward a sample of molecular clouds in the inner Galaxy, all containing dense clumps that are actively engaged in star formation. We compare these two molecular line tracers with millimeter continuum emission and extinction, as inferred from 13CO, as tracers of dense gas in molecular clouds. The fraction of the line luminosity from each tracer that comes from the dense gas, as measured by mag, varies substantially from cloud to cloud. In all cases, a substantial fraction (in most cases, the majority) of the total luminosity arises in gas below the mag threshold and outside the region of strong millimeter continuum emission. Measurements of toward other galaxies will likely be dominated by such gas at lower surface densities. Substantial, even dominant, contributions to the total line luminosity can arise in gas with densities typical of the cloud as a whole (n?~?100 cm?3). Defining the dense clump from the HCN or emission itself, similarly to previous studies, leads to a wide range of clump properties, with some being considerably larger and less dense than in previous studies. HCN and have a similar ability to trace dense gas for the clouds in this sample. For the two clouds with low virial parameters, 13CO is definitely a worse tracer of the dense gas, but for the other four, it is equally good (or bad) at tracing dense gas.
KeywordInterstellar medium Molecular clouds Star formation
WOS IDIOP:0004-637X-894-2-ab8938
PublisherThe American Astronomical Society
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Document Type期刊论文
Affiliation1.Department of Astronomy The University of Texas at Austin 2515 Speedway, Stop C1400 Austin, TX 78712-1205, USA;
2.Korea Astronomy and Space Science Institute 776 Daedeokdae-ro, Yuseong-gu Daejeon, 34055, Republic of Korea
3.Humanitas College, Global Campus, Kyung Hee University, Yongin-shi 17104, Republic of Korea
4.University of Science and Technology, Korea (UST), 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Republic of Korea
5.National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, 100012, People’s Republic of China
6.Department of Astronomy University of Massachusetts Amherst, MA 01003, USA
7.Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai, 200030, People’s Republic of China
8.McMaster University, 1 James St N, Hamilton, ON, L8P 1A2, Canada
9.Graduate School of Natural Sciences, Nagoya City University, Mizuho-ku, Nagoya, Aichi 467-8601, Japan
10.IBM Canada, 120 Bloor Street East, Toronto, ON, M4Y 1B7, Canada
11.Haystack Observatory MIT 99 Milstone Rd., Westford, MA 01886, USA
Recommended Citation
GB/T 7714
Evans,Neal J.,Kim,Kee-Tae,Wu,Jingwen,等. Star Formation Occurs in Dense Gas, but What Does “Dense” Mean?[J]. The Astrophysical Journal,2020,894(2).
APA Evans,Neal J..,Kim,Kee-Tae.,Wu,Jingwen.,Chao,Zhang.,Heyer,Mark.,...&Kauffmann,Jens.(2020).Star Formation Occurs in Dense Gas, but What Does “Dense” Mean?.The Astrophysical Journal,894(2).
MLA Evans,Neal J.,et al."Star Formation Occurs in Dense Gas, but What Does “Dense” Mean?".The Astrophysical Journal 894.2(2020).
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