Photon-dominated chemistry in the nucleus of M82:: Widespread HOC+ emission in the inner 650 parsec disk
Photon-dominated chemistry in the nucleus of M82:: Widespread HOC+ emission in the inner 650 parsec disk
复制标题
DOI：
10.1086/427990
复制
发表时间：
2005-02-01
影响因子：
4.9
通讯作者：
de Vicente, P
中科院分区：
文献类型：
--
作者：
Fuente, A;García-Burillo, S;de Vicente, P
使用IRAM 30 m望远镜，M82的核已被绘制成CN、HCN、C2 H、c-C3 H2、CH 3C 2 H、HC 3 N和HOC+的几条3和1 mm谱线。这些物种已被有意选择作为光子主导化学的良好示踪剂。我们在650 pc星系盘内部测量到[CN]/[HCN]类似于5。此外，我们已经检测到HOC+ 1 -> 0线，其强度与（HCO+）-C-13 1 -> 0线的强度相似。这意味着[HCO+]/[HOC+]的比值接近40。这些结果证实了在M82核中存在一个巨大的光解区。事实上，低的[HCO+]/[HOC+]比率只能解释为M82的核是由小的（r < 0.02-0.2 pc）和密集的（n是10（4）- 10（5）cm（-3）的几倍）云形成的，这些云浸没在强紫外光场中（G（0）= 10（4），以哈宾场为单位）。在M82的核中检测到碳氢化合物c-C3 H2和CH 3C 2 H，表明在这个巨大的PDR中正在发展复杂的碳化学。
The nucleus of M82 has been mapped in several 3 and 1 mm lines of CN, HCN, C2H, c-C3H2, CH3C2H, HC3N, and HOC+ using the IRAM 30 m telescope. These species have been purposely selected as good tracers of photon-dominated chemistry. We have measured [CN]/[HCN] similar to 5 in the inner 650 pc galaxy disk. Furthermore, we have detected the HOC+ 1 --> 0 line with an intensity similar to that of the (HCO+)-C-13 1 --> 0 line. This implies an [HCO+]/[HOC+] ratio of similar to40. These results corroborate the existence of a giant photodissociation region (PDR) in the nucleus of M82. In fact, the low [HCO+]/[HOC+] ratio can only be explained if the nucleus of M82 is formed by small (r < 0.02-0.2 pc) and dense (n ∼ a few times 10(4) - 10(5) cm(-3)) clouds immersed in an intense UV field (G(0) ∼ 10(4) in units of the Habing field). The detection of the hydrocarbons c-C3H2 and CH3C2H in the nucleus of M82 suggests that a complex carbon chemistry is developing in this giant PDR.