Methanol detection in M 82
Methanol detection in M 82
复制标题
M 82 中的甲醇检测
DOI：
--
复制
发表时间：
2006
期刊：
影响因子：
--
通讯作者：
R. Mauersberger
中科院分区：
文献类型：
--
作者：
S. Martín;J. Martín;R. Mauersberger
上下文与其他星暴星系相比，M82的核星暴区显示出一些复杂分子的系统低丰度。这可能与推测的光解离主导的环境有关。具体地，已知甲醇显示相对低的丰度，因为其容易光解离。目标。我们提出了一个多层次的研究甲醇的排放，在这个星系中首次检测到，并讨论其排放的起源。方法.观测到CH 3OH向M82中心的三次跃迁和在核周围的两次跃迁。两个不同的组件被发现，一个具有高激发（$n，
m H_2）sim 10^6~cm^{-3}$，$T_{
2019 - 05 - 20 00：00 0
m H_2）sim 10^4~cm^{-3}$，$T_{
m rot}sim 5$ K）。结果只有考虑到从尘埃颗粒中注入的甲醇，才能解释观测到的高达几个10 - 9的甲醇丰度。虽然整体的[ CH 3 OH] /[ NH 3 ]比比在其他恒星爆发中观察到的要大得多，但密集的高激发分量显示出与NGC 253和Maffei 2相似的值。结论.我们的观测结果表明，M82的分子物质是由致密的温暖核心形成的，屏蔽了紫外线辐射，类似于其他恒星爆发中的分子云，周围环绕着密度较低的光解晕。致密温暖的核心很可能是M 82内最近和未来星星形成的位置。
Context. The nuclear starburst region in M 82 shows systematical low abundances of some complex molecules when compared with other starburst galaxies. This is likely related to a presumably photodissociation dominated environment. In particular, methanol is known to show relatively low abundance because it is easily photodissociated. Aims. We present a multilevel study of the emission of methanol, detected for the first time in this galaxy, and discuss the origin of its emission. Methods. Observations of three transitions of CH 3 OH towards the center and two positions around the nucleus of M 82 are presented. Two different components are found, one with high excitation ($n(
m H_2)sim 10^6~cm^{-3}$, $T_{
m rot}sim 20$ K) and the other with low excitation ($n(
m H_2)sim 10^4~cm^{-3}$, $T_{
m rot}sim 5$ K). Results. The high observed methanol abundance of a few 10 -9 can only be explained if injection of methanol from dust grains is taken into account. While the overall [ CH 3 OH] /[ NH 3 ] ratio is much larger than observed towards other starbursts, the dense high excitation component shows a similar value to that found in NGC 253 and Maffei 2. Conclusions. Our observations suggest the molecular material in M 82 to be formed by dense warm cores, shielded from the UV radiation and similar to the molecular clouds in other starbursts, surrounded by a less dense photodissociated halo. The dense warm cores are likely the location of recent and future star formation within M 82.