M51星系盘上HCN J=1-0发射线的成图观测

发布时间：2018-01-13 10:56

本文关键词：M51星系盘上HCN J=1-0发射线的成图观测　出处：《中国科学:物理学力学天文学》2014年09期 　论文类型：期刊论文

【摘要】：为了解致密分子气体在星系盘上的分布,我们使用IRAM 30 m望远镜对M51的HCN J=1-0分子发射线进行了成图观测(角分辨率为28").成图区域达4'×5'(1'~2.9 kpc),是目前为止对M51 HCN J=1-0发射线进行的最为延展的一次成图观测.将之与NRO 45 m望远镜观测得到的CO J=1-0发射线数据进行比较,我们对M51星系内致密分子气体与总分子气体分布的差异与相关性等特性进行了讨论.HCN分布呈现出向星系中心集中的趋势,中心区域的HCN积分强度是星系盘上的3 4倍.在HCN积分强度图中也观测到了由CO发射所示踪的气体旋臂.M51总HCN光度是中心主波束区域(kpc尺度)的5倍,这说明了依然存在很多的致密分子气体分布在星系中心核区之外.在距星系光学中心42''内的区域(包含核球区的星系内盘),距离星系中心越远,HCN/CO的积分强度比越小;而在远离星系中心的星系盘上(大于42")该比值基本保持恒定.对于星系盘上的大部分区域,IHCN和ICO具有非常紧密的线性相关性,最小二乘法拟合的斜率为1.2.而对于核球区它们的拟合斜率则要高得多(2.3).所有这些都说明了致密分子气体的性质(例如含量、发射条件、HCN的丰度)在核球区和星系盘上是不一样的.
[Abstract]:In order to understand the distribution of dense molecular gas on galactic disk. Using the IRAM 30m telescope, we have mapped the emission lines of M51's HCN JJ _ (1-0) molecule (angular resolution is 28 "). The mapping area is 4'脳 5 ~ (-1). (2. 9 kpcs). Is by far the most extended mapping observation of the M51 HCN JJ 1-0 emission line. Co obtained from the NRO 45 m telescope. JN1-0 emission line data were compared. We discuss the difference and correlation between the distribution of dense molecular gas and total molecular gas in M51 galaxy. HCN distribution tends to be concentrated towards the center of the galaxy. The HCN integral intensity in the central region is 3 on the disk. In the HCN integral intensity diagram, the total HCN luminosity of the gas rotation arm. M51, which is traced by CO emission, is also observed to be the central main beam region (. Kpc scale). This indicates that there are still a lot of dense molecular gases distributed outside the central nucleus of the galaxy, and the region within 42 'from the optical center of the galaxy (the inner disk of the galaxy containing the sphere of nucleus) is further away from the center of the galaxy. The smaller the integral intensity ratio of HCN/CO is; On the disk far away from the center of the galaxy (> 42 "), the ratio is basically constant. There is a very close linear correlation between IHCN and ICO for most of the region of the disk. The slope fitted by the least square method is 1.2, and the slope is much higher for the nuclear sphere. All these indicate the properties of the dense molecular gas (such as content, emission condition). HCN abundance) is different in the nuclear sphere from the galactic disk.
【作者单位】：中国科学院紫金山天文台;中国科学院大学;中国科学院射电天文重点实验室;
【基金】：国家自然科学基金资助项目(批准号:11173059)
【分类号】：P152
【正文快照】： 大量的观测研究表明,恒星形成于巨型分子云中(其主要成分是氢分子),并且恒星形成活动非常依赖于局域密度,这就是类星体红移发现者提出的Schmidt恒星形成定律[1].在巨型分子云中,CO分子的丰度仅次于氢分子,其转动跃迁(尤其是J=1-0跃迁)在平均密度大于约300 cm?3的区域就很容易

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