论文标题
仙女座银河系中单个巨型分子云的首次解决尘埃连续测量
First Resolved Dust Continuum Measurements of Individual Giant Molecular Clouds in the Andromeda Galaxy
论文作者
论文摘要
在我们当地的银河邻居中，最好使用灰尘测量的组合来研究分子云，以确定云的稳健质量，大小和内部结构以及分子线观测值，以确定云动力学和化学。我们在这里介绍了一个计划的第一个结果，旨在将此类研究扩展到麦哲伦云之外的附近星系。利用230 GHz的亚毫升阵列（SMA）的宽带升级，我们在Andromeda Galaxy（M31）中获得了亚GMC量表（$ \ sim $ 15 pc）上热灰尘发射（M31）的第一个连续探测。其中包括从麦芽云层以外的单个GMC尘埃发射的第一个解决连续性检测。利用SMA的强大功能，我们同时录制了CO（2-1）发射，并以相同的$（u，\，v）$覆盖范围，星形测量和校准，实现了CO转换因子的首次测量，$α_ {\ rm \ rm \，CO（2-1）$，co（2-1）$，co（2-1）$，co（2-1）。我们的直接测量得出的平均共二线质量转换系数为$α^\ prime _ {\ rm co-dust} = 0.042 \ pm0.018 $ $ $ $ $ m_ \ odot $（km s $ s $ s $^{ - 1} $ pc $ pc $^2 $^2 $^2 $^{ - 1} $^{ - 1} $^{ - 1} $ for $ j = 2-1 $ j = 2-1 $该值似乎不会随着半乳酸半径而变化。假设恒定的气体涂料比为136，则产生的$α_ {\ rm co} $ = $ 5.7 $ = $ 5.7 $ \ pm $ 2.4 $ 2.4 $ m_ \ odot $（k km s $ s $^{ - 1} $ pc $^2 $^2 $^2 $）$^{ - 1} $ for 2-1 triveltion for 2-1 trivelition cy of Milky of Milky of Gmcs of Milky of Gmccs of Milky of Gmccs of Milky of Milky of Gmccs except。最后，使用相同的分析技术，我们将结果与局部猎户座分子云的观测结果进行比较，该云位于M31的距离处，并模拟了SMA观察到的情况。
In our local Galactic neighborhood, molecular clouds are best studied using a combination of dust measurements, to determine robust masses, sizes and internal structures of the clouds, and molecular-line observations to determine cloud kinematics and chemistry. We present here the first results of a program designed to extend such studies to nearby galaxies beyond the Magellanic Clouds. Utilizing the wideband upgrade of the Submillimeter Array (SMA) at 230 GHz we have obtained the first continuum detections of the thermal dust emission on sub-GMC scales ($\sim$ 15 pc) within the Andromeda galaxy (M31). These include the first resolved continuum detections of dust emission from individual GMCs beyond the Magellanic Clouds. Utilizing a powerful capability of the SMA, we simultaneously recorded CO(2-1) emission with identical $(u,\,v)$ coverage, astrometry and calibration, enabling the first measurements of the CO conversion factor, $α_{\rm\,CO(2-1)}$, toward individual GMCs across an external galaxy. Our direct measurement yields an average CO--to--dust mass conversion factor of $α^\prime_{\rm CO-dust} = 0.042\pm0.018$ $M_\odot$ (K km s$^{-1}$ pc$^2$)$^{-1}$ for the $J= 2-1$ transition. This value does not appear to vary with galactocentric radius. Assuming a constant gas-to-dust ratio of 136, the resulting $α_{\rm CO}$ $=$ 5.7 $\pm$ 2.4 $M_\odot$ (K km s$^{-1}$ pc$^2$)$^{-1}$ for the 2-1 transition is in excellent agreement with that of Milky Way GMCs, given the uncertainties. Finally, using the same analysis techniques, we compare our results with observations of the local Orion molecular clouds, placed at the distance of M31 and simulated to appear as they would if observed by the SMA.
