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arXiv 2602.09871astro-ph.GA
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仙女座星系巨分子云中的尘埃发射与CO同位素

Resolved Dust Emission and CO Isotopologues in Giant Molecular Clouds of the Andromeda Galaxy

University of Hertfordshire（赫特福德大学）；Harvard & Smithsonian（哈佛大学与史密森尼学会）；Massachusetts Institute of Technology（麻省理工学院）

Chloe Bosomworth, Jan Forbrich, Charles J. Lada, Glen Petitpas

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ApJ, in press
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AI总结：

本文研究了仙女座星系巨分子云中尘埃发射与CO同位素的关系，通过高分辨率观测确定尘埃质量与光度比，并发现80%的GMC区域接近virial平衡。

摘要：

亚毫米波段的尘埃发射可以用来可靠地追踪分子云的基本性质。最近对仙女座星系（M31）的亚毫米波阵列（SMA）调查的早期结果包括对个体巨分子云（GMC）的首次分辨尘埃连续发射的探测。本文更新了现在完成的SMA调查，该调查对M31中的80个赫尔斯识别的巨分子关联（GMAs）进行了调查。SMA调查同时探测了230 GHz的尘埃连续发射以及$J = 2 \rightarrow 1$跃迁的CO同位素$^{12}\rm CO$、$^{13}\rm CO$和$\rm C^{18}O$，空间分辨率为$\lesssim 15~\mathrm{pc}$。在71个云核心中检测到尘埃连续发射，其中26个被分辨。这使样本规模翻了一番多。通过将尘埃和CO观测与相同的天文学测量进行比较，我们直接测量了尘埃质量与光度比，$\rm α^{\prime}_{^{12}CO}$和$\rm α^{\prime}_{^{13}CO}$。我们得出对于扩大样本的$<α^{\prime}_{\rm ^{12}\rm CO}>~=~0.070~\pm~0.031~M_{\odot}\,(\rm K~km~s^{-1}~pc^{2})^{-1}$和$<α^{\prime}_{\rm ^{13}\rm CO}>~=~0.37~\pm~0.20~M_{\odot}\,(\rm K~km~s^{-1}~pc^{2})^{-1}$，这些值与之前报告的值一致。通过virial分析，我们发现被分辨尘埃发射追踪的80%的GMC区域是束缚的且接近virial平衡。最后，我们通过结合SMA观测与现有MMT/Hectospec光学光谱学数据对$\rm α^{\prime}_{\rm CO}$的金属licity依赖性进行了更新分析。我们发现$\rm α^{\prime}_{\rm CO}$与金属licity之间没有趋势，支持之前的发现。

英文摘要：

Dust emission at submillimeter wavelengths can be used to reliably trace the basic properties of molecular clouds. Early results from a recent Submillimeter Array (SMA) survey of the Andromeda Galaxy (M31) include the first detections of resolved dust continuum emission from individual giant molecular clouds (GMCs) in an external spiral galaxy. This paper updates on the now-complete SMA survey of 80 Herschel-identified giant molecular associations (GMAs) in M31. The SMA survey simultaneously probes dust continuum emission at 230 GHz and the $J = 2 \rightarrow 1$ transitions of the CO isotopologues, $^{12}\rm CO$, $^{13}\rm CO$, and $\rm C^{18}O$ at a spatial resolution of $\lesssim 15~\mathrm{pc}$. Dust continuum emission was detected in 71 cloud cores, of which 26 were resolved. This more than doubles the size of the previous sample. By comparing dust and CO observations with identical astrometry, we directly measure the dust mass to-light ratios, $\rm α^{\prime}_{^{12}CO}$, and $\rm α^{\prime}_{^{13}CO}$. We derive $<α^{\prime}_{\rm ^{12}\rm CO}>~=~0.070~\pm~0.031~M_{\odot}\,(\rm K~km~s^{-1}~pc^{2})^{-1}$ and $<α^{\prime}_{\rm ^{13}\rm CO}>~=~0.37~\pm~0.20~M_{\odot}\,(\rm K~km~s^{-1}~pc^{2})^{-1}$ for the increased sample, which are in agreement with previously reported values. From virial analysis, we find that 80% of the GMC regions traced by resolved dust emission are bound and close to virial equilibrium. Finally, we update our analysis on the metallicity dependence of $\rm α^{\prime}_{\rm CO}$ by combining SMA observations with existing MMT/Hectospec optical spectroscopy toward H II regions. We find no trend in $\rm α^{\prime}_{\rm CO}$ with metallicity, supporting the previous findings.

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