The distribution and origin of C2H in NGC 253 from ALCHEMI
The distribution and origin of C2H in NGC 253 from ALCHEMI
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ALCHEMI NGC 253 中 C2H 的分布和来源
DOI：
10.1051/0004-6361/202141233
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发表时间：
2021
影响因子：
6.5
通讯作者：
van der Werf P.
中科院分区：
文献类型：
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作者：
Holdship J.;Viti S.;Martin S.;Harada N.;Mangum J.;Sakamoto K.;Muller S.;Tanaka K.;Yoshimura Y.;Nakanishi K.;Herrero-Illana R.;Muehle S.;Aladro R.;Colzi L.;Emig K. L.;Garcia-Burillo S.;Henkel C.;Humire P.;Meier D. S.;Rivilla V. M.;van der Werf P.
对化学物质的观察可以提供对发射气体的物理条件的见解，但重要的是要了解它们的丰度和激发在不同的加热环境中如何变化。C2H是一种通常在银河系PDR区域发现的分子，但有证据表明，它也可以追踪到其他区域在河外环境中经历的能量处理。作为ALCHEMI ALMA大型项目的一部分，我们以1.6″（28 pc）分辨率绘制了附近星爆星系NGC 253中心分子区C2H的发射图，并对其进行了表征，以了解其化学起源。方法利用n = 1−0到n = 4−3的C2H旋转转变的光谱模型，推导出ngc253中C2H柱向致密云的密度。然后，我们使用化学模型，包括光解离区（PDR），密集云和冲击模型来研究产生分子发射的化学过程和物理条件。结果在NGC 253的密集区检测到高C2H柱密度，约为1015cm−2。我们进一步发现，如果假设发射来自云边缘的PDR区域，这些柱密度就不能重现。相反，我们发现即使在这些云的高视觉消光内部，C2H丰度仍然很高，这很可能是由高宇宙射线电离率引起的。
ContextObservations of chemical species can provide insights into the physical conditions of the emitting gas however it is important to understand how their abundances and excitation vary within different heating environments. C2H is a molecule typically found in PDR regions of our own Galaxy but there is evidence to suggest it also traces other regions undergoing energetic processing in extragalactic environments.AimsAs part of the ALCHEMI ALMA large program, we map the emission of C2H in the central molecular zone of the nearby starburst galaxy NGC 253 at 1.6″ (28 pc) resolution and characterize it to understand its chemical origins.MethodsWe used spectral modeling of theN= 1−0 throughN= 4−3 rotational transitions of C2H to derive the C2H column densities towards the dense clouds in NGC 253. We then use chemical modeling, including photodissociation region (PDR), dense cloud, and shock models to investigate the chemical processes and physical conditions that are producing the molecular emission.ResultsWe find high C2H column densities of ∼1015cm−2detected towards the dense regions of NGC 253. We further find that these column densities cannot be reproduced if it is assumed that the emission arises from the PDR regions at the edge of the clouds. Instead, we find that the C2H abundance remains high even in the high visual extinction interior of these clouds and that this is most likely caused by a high cosmic-ray ionization rate.
NGC 1068 的 λ = 3 mm 分子谱线调查 AGN 环境的化学特征。
DOI：
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发表时间：
2021
期刊：
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影响因子：
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作者：
R. Aladro;S. Viti;E. Bayet;D. Riquelme;S. Martín;R. Mauersberger;J. Martín;A. M.;Requena;C. Kramer;A. Weiss
通讯作者：
A. Weiss
CCH N = 4-3 来自致密星际云的发射
影响因子：
6.5
作者：
G. Watt;G. White;T. Millar;A. Ardenne
通讯作者：
A. Ardenne