Dense gas in nearby galaxies - XVI. The nuclear starburst environment in NGC 4945

doi:10.1051/0004-6361:20035722

淡江大學機構典藏 > 理學院 > 物理學系暨研究所 > 期刊論文 > Item 987654321/27840

請使用永久網址來引用或連結此文件: https://tkuir.lib.tku.edu.tw/dspace/handle/987654321/27840

題名:	Dense gas in nearby galaxies - XVI. The nuclear starburst environment in NGC 4945
作者:	Wang, M.;Henkel, C.;秦一男;Chin, Yi-nan;Whiteoak, J. B.;Hunt, M.;Cunningham, Mauersberger R.;Muders, D.
貢獻者:	淡江大學物理學系
日期:	2004-08
上傳時間:	2009-12-31 10:47:40 (UTC+8)
出版者:	Les Ulis: EDP Sciences
摘要:	A multi-line millimeter-wave study of the nearby starburst galaxy NGC 4945 has been carried out using the Swedish-ESO Submillimeter Telescope (SEST). The study covers the frequency range from 82 GHz to 354 GHz and includes 80 transitions of 19 molecules. 1.3 mm continuum data of the nuclear source are also presented. A large number of molecular species indicate the presence of a prominent high density interstellar gas component characterized by n H 2 ∼10 5 cm −3 . Abundances of molecular species are calculated and compared with abundances observed toward the starburst galaxies NGC 253 and M 82 and galactic sources. Apparent is an `overabundance' of HNC in the nuclear environment of NGC 4945. While the HNC/HCN J =1--0 line intensity ratio is ∼ 0.5, the HNC/HCN abundance ratio is ∼ 1. While HCN is subthermally excited (T ex ∼ 8 K), CN is even less excited (T ex ∼ 3--4 K), indicating that it arises from a less dense gas component and that its N =2--1 line can be optically thin even though its N =1--0 emission is moderately optically thick. Overall, fractional abundances of NGC 4945 suggest that the starburst has reached a stage of evolution that is intermediate between those observed in NGC 253 and M 82. Carbon, nitrogen, oxygen and sulfur isotope ratios are also determined. Within the limits of uncertainty, carbon and oxygen isotope ratios appear to be the same in the nuclear regions of NGC 4945 and NGC 253. High 18 O/ 17 O, low 16 O/ 18 O and 14 N/ 15 N and perhaps also low 32 S/ 34 S ratios appear to be characteristic properties of a starburst environment in which massive stars have had sufficient time to affect the isotopic composition of the surrounding interstellar medium.
關聯:	Astronomy & Astrophysics 422(3), pp.883-905
DOI:	10.1051/0004-6361:20035722
顯示於類別:	[物理學系暨研究所] 期刊論文

文件中的檔案:

檔案	描述	大小	格式	瀏覽次數
0004-6361_422(3)p883-905.pdf		1099Kb	Adobe PDF	535	檢視/開啟
index.html		0Kb	HTML	40	檢視/開啟

在機構典藏中所有的資料項目都受到原著作權保護.

TAIR相關文章

資料載入中.....