arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1901.01124astro-ph.SRastro-ph.GA
收藏

普朗克星系冷团的C2H N=1-0和N2H + J=1-0观测

C2H N=1-0 and N2H+ J=1-0 observations of Planck Galactic cold clumps

Xunchuan Liu, Yuefang Wu, Chao Zhang, Tie Liu, Jinghua Yuan, Sheng-Li Qin, Bing-gang Ju, Li-Xin Li

备注：
23 pages, 6 figures, 5 tables
发表信息：
A&A 622, A32 (2019)
阅读 PDF
arXiv 页面 ↗HTML 原文 ↗

摘要：

利用紫金山天文台13.7 m望远镜对普朗克银河系冷团（PGCC）进行了C2 H N=1-0和N2 H + J=1-0的巡天观测。选择C_2H和N_2H ~+研究PGCCs的化学演化状态。在观察到的121个与PGCC相关的分子核中，分别检测到71个和58个C2 HN =1-0和N2 H + J=1-0。大多数源的检测线可以用具有兼容Vlsr和线宽的单个分量拟合，这证实了这些PGCC核心非常冷（气体温度为9-21 K）并且静止，同时仍然由湍流主导。C_2H和N_2H ~+柱密度之比（N（C_2H）/N（N_2H ~+））是PGCC核演化状态的良好示踪剂。气粒化学模型可以再现N（C2 H）/N（N2 H+）随时间的下降趋势。N2 H+丰度最低（X[N2 H +] < 10^{-10}）的岩心最年轻，C2 H丰度几乎恒定。在含X[N2 H +] ~ 1 E-9的演化核中，C2 H的丰度随着碳原子的耗尽而迅速下降。虽然这些PGCC核心处于不同的演化状态，但它们都很年轻（<5E 5年），N（C2 H）> N（N2 H+）。对20个PGCC岩心进行了成图观测。与金牛座相比，仙王座的PGCC核心具有较低的N（C2 H）/N（N2 H+）和较大的线宽。这意味着金牛座的PGCC核心比仙王座的化学演化要少。

英文摘要：

A survey of C2H N=1-0 and N2H+ J=1-0 toward Planck Galactic cold clumps (PGCCs) was performed using the Purple Mountain Observatory's 13.7 m telescope. C2H and N2H+ were chosen to study the chemical evolutionary states of PGCCs. Among 121 observed molecular cores associated with PGCCs, 71 and 58 are detected with C2H N=1-0 and N2H+ J=1-0, respectively. The detected lines of most sources can be fitted with a single component with compatible Vlsr and line widths, which confirms that these PGCC cores are very cold (with gas temperatures 9-21 K) and quiescent while still dominanted by turbulence. The ratio between the column densities of C2H and N2H+ (N(C2H)/N(N2H+)) is found to be a good tracer for the evolutionary states of PGCC cores. Gas-grain chemical model can reproduce the decreasing trend of N(C2H)/N(N2H+) as a function of time. The cores with the lowest abundances of N2H+ (X[N2H+] < 10^{-10}) are the youngest, and have nearly constant abundances of C2H. In evolved cores with X[N2H+] ~ 1E-9, abundances of C2H drop quickly as the exhaustion of carbon atoms. Although these PGCC cores are in different evolutionary states, they are all quite young (<5E5 yr) with N(C2H) > N(N2H+). Mapping observations are carried out toward 20 PGCC cores. The PGCC cores in Cepheus have lower N(C2H)/N(N2H+) and larger line widths compared with those in Taurus. This implies that PGCC cores in Taurus are less chemically evolved than those in Cepheus.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

↑