A fragmentary cold H I cloud near W3 and W4
A fragmentary cold H I cloud near W3 and W4
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W3 和 W4 附近有零散的冷 H I 云
DOI：
10.1086/113355
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Y. Fukui
中科院分区：
文献类型：
--
作者：
T. Hasegawa;F. Sato;Y. Fukui
在W3和W 4附近的巨分子云内部和周围的21厘米谱线剖面中，冷的H I云表现为自吸收下降。云几乎沿着银道面从W 4的西部边缘延伸到大约150 pc西。冷氢云由几个碎片组成，通常直径约为25秒差距。它们的分布与CO云的分布部分一致，而碎片被发现远远超出了CO检测的极限。碎片中的总颗粒密度估计为20- 35 cm/sup-3/，相当于（H/sub 2/）/（H I）比为15- 50。每个碎片都没有显示出系统运动的迹象，如旋转或塌陷。由维里定理推断出的碎片质量为（1--4）× 10 ~ 4/sup ~ 4/ M/sub ~ sun/，所有碎片的H ~ I云的总质量加起来等于或大约等于10 ~ 4/sup ~ 4/M/sub ~ sun/。=1.7 x 10/sup 5/ M/sub sun/。这表明，W3/W 4分子云复合物的质量是由一个因素约。2比CO观测估计。在邻近H II区域的CO亮度增强层处，H I dipmore »突然消失，表明（H/sub 2/）/（H I）比在那里更大。«少
A cold H I cloud appears as self-absorption dips in the 21-cm line profiles in and around the giant molecular cloud near W3 and W4. The cloud extends nearly along the galactic plane from the western edge of W4 to approx.150 pc west. The cold H I cloud consists of several fragments typically approx.25 pc in diameter. Their distribution coincides in part with that of the CO cloud, while the fragments are found well beyond the limit of the CO detection. The total particle density in the fragments is estimated to be 20--35 cm/sup -3/, which corresponds to the (H/sub 2/)/(H I) ratio of 15--50. Each fragment shows no sign of systematic motions such as rotation or collapse. The mass of a fragment inferred from the virial theorem is (1--4) x 10/sup 4/ M/sub sun/ and the total mass of the H I cloud summed up for all the fragments amounts to > or approx. =1.7 x 10/sup 5/ M/sub sun/. This indicates that the mass of the W3/W4 molecular-cloud complex is larger by a factor of approx.2 than that estimated by CO observations. At the layer of enhanced CO brightness adjoining the H II region, the H I dipmore » disappears suddenly suggesting that the (H/sub 2/)/(H I) ratio is larger there.« less