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Massive star forming environments.

Devine, Kathryn Elizabeth.

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Massive star forming environments.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Massive star forming environments./
作者:	Devine, Kathryn Elizabeth.
面頁冊數:	122 p.
附註:	Source: Dissertation Abstracts International, Volume: 71-10, Section: B, page: 6169.
Contained By:	Dissertation Abstracts International71-10B.
標題:	Physics, Astronomy and Astrophysics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3424059
ISBN:	9781124225463

Massive star forming environments.
Devine, Kathryn Elizabeth.

Massive star forming environments. - 122 p.

Source: Dissertation Abstracts International, Volume: 71-10, Section: B, page: 6169.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2010.

We present a study of the earliest stages of massive star formation, in which we focus on Infrared Dark Clouds (IRDCs) and young massive clusters. We present Very Large Array spectral line observations of ammonia (NH 3) and CCS toward four IRDCs. The NH3 lines provide diagnostics of the temperature and density structure within IRDCs. Based upon the NH 3 column density, IRDCs have masses of &sim; 103 to 10 4 M&odot; . We detect twenty NH3 clumps within four IRDCs, with radii < 0.3 pc and masses &sim; 102 to 103 M&odot; . A majority of the clumps are associated with signatures of star formation: 24 mum emission, H2O masers, 8 GHz continuum emission, and/or outflows. The physical properties of the clumps are consistent with massive cluster progenitors. From the NH3 emission we also find distinct velocity components, or "subclouds", within each IRDC. Although they appear ubiquitous in IRDCs, subclouds have not previously been reported. Subclouds may represent an intermediate stage of molecular cloud fragmentation, between filamentary structure and clump formation. The spatial distribution of the CCS and NH3 emission is generally anti-correlated, with the NH 3 predominantly in the high-density clumps, and CCS in lower-density gas. This spatial distribution may be explained by chemical evolution models for star forming gas, where in chemically young clouds with recently disrupted gas CCS forms quickly. In early clump formation CCS is abundant and in the centers of more evolved star forming clumps CCS is depleted. Near infrared observations of three embedded massive star forming regions are presented from the Near Infrared Imager (NIRIM) camera on the 3.5 m WIYN telescope. We report J, H, and K' band photometry in the clusters AFGL437, AFGL5180, and AFGL5142 and use these results to probe the stellar populations, extinction, and ages of the clusters. We find that all three clusters suffer significant extinction (AK &sim;1), have ages ≤ 5 Myr, and are actively forming stars. We conclude that the properties of these embedded clusters are consistent with their evolving from IRDC clumps.

ISBN: 9781124225463Subjects--Topical Terms:

1019521
Physics, Astronomy and Astrophysics.

Massive star forming environments.
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