Dense gas in nearby galaxies: VIII. The detection of OCS
學年 83
學期 2
出版（發表）日期 1995-02-01
作品名稱 Dense gas in nearby galaxies: VIII. The detection of OCS
作品名稱（其他語言）
著者 Chin, Y.N.; R. Mauersberger, C. Henkel
單位 淡江大學物理學系
出版者 Les Ulis: EDP Sciences
著錄名稱、卷期、頁數 Astronomy and Astrophysics 294, pp.23-32
摘要 The detection of extragalactic OCS, the heaviest molecule identified outside the Galaxy, is reported in three rotational transitions toward the bulge of NGC253. Toward M82, OCS has been tentatively detected. Abundances are consistent with models for warm, dense clouds which have not yet reached chemical equilibrium or with the frequent erosion of grain mantles by C-shocks. This can also explain the large abundances of complex molecules in NGC253. Densities and temperatures of the OCS emitting gas are compared with results from other molecular tracers. From model computations, OCS in the center of NGC253 is emitted by a moderately dense molecular component with n(H2) ~ 103.4 /cm3. This component makes up the bulk of the molecular gas mass. Other molecules also reveal the presence of a much denser component with 10(5-5.5) /cm3. A molecular gas mass of ~ 2 × 108 solar masses is estimated for a 180pc sized molecular cloud toward the center of NGC253; the mean H2 density is ~ 2000 /cm3; and the mean H2 column density, 7 × 1023 /cm2, corresponds to a visual extinction of 700m. The relative OCS abundance is X(OCS) ~ 10-8.9. From detections of the J=2-1 and 3-2 transitions of C34S, the density of the dense molecular gas toward the nuclear region of IC342 is n(H2) ~ 104.6 /cm3. Also presented are a possible detection of the HC3N J=16-15 line toward IC342 and upper limits for the emission of the DCN J=2-1 line toward NGC253 and IC342. For NGC253, [DCN]/[HCN] <= 4 × 10-3.
關鍵字
語言 en
ISSN 0004-6361 1432-0746
期刊性質 國外
收錄於 SCI
產學合作
通訊作者
審稿制度
國別 FRA
公開徵稿
出版型式 紙本 電子版
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