The ATLASGAL survey: distribution of cold dust in the Galactic plane - Combination with Planck data
The ATLASGAL survey: distribution of cold dust in the Galactic plane - Combination with Planck data
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DOI：
10.1051/0004-6361/201526639
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发表时间：
2015-11
影响因子：
6.5
通讯作者：
T. Csengeri;A. Weiss;F. Wyrowski;K. Menten;J. Urquhart;S. Leurini;F. Schuller;H. Beuther;S. Bontemps;L. Bronfman;T. Henning;N. Schneider;N. Schneider
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文献类型：
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作者：
T. Csengeri;A. Weiss;F. Wyrowski;K. Menten;J. Urquhart;S. Leurini;F. Schuller;H. Beuther;S. Bontemps;L. Bronfman;T. Henning;N. Schneider;N. Schneider
上下文灵敏的地基亚毫米波测量，如ATLASGAL，提供了一个关于银河系平面中冷致密气体分布的全球视图，与最近的赫歇尔天基测量相比，其角分辨率高达两倍。然而，基于地面的连续观测的缺点是，当在数据处理中减去天空噪声时，它们在大于阵列视场的一小部分的角度尺度上固有地过滤发射。但是，丢失的关于漫射发射分布的信息可以从普朗克的天基全天巡天中恢复。目标。在这里，我们的目标是演示如何使用这些信息来补充地面测辐射热计数据，并提出APEX望远镜大面积银河系巡天（ATLASGAL）调查的再处理地图。方法.我们使用的地图在353 GHz的普朗克/HFI仪器，进行了高灵敏度的全天空调查的频率接近的APEX/LABOCA阵列，这是集中在345 GHz。作为对地面观测的补充，这些地图提供了更大角度尺度的信息，揭示了银河系内部冷尘埃的分布，空间动态范围更大。我们直观地描述所观察到的功能和评估的全球性的灰尘分布。结果从大的角度尺度添加信息有助于更好地识别冷银河系星际介质的全局属性。为了说明这一点，我们提供了从尘埃到W 43恒星形成区的质量估计，并估计低强度晕和恒星形成脊之间的柱密度对比至少为5倍。我们还展示了在0.5°角尺度上延伸的细长结构的例子，我们称之为薄巨丝。对应于距离为3千秒差距的投影中> 30秒差距的结构，这些尘埃带非常延伸，并显示出大的纵横比。我们评估致密气体的分数，通过确定的APEX/LABOCA地图的组合地图的贡献，估计2？在银河系平面内，致密气体部分（对应于Av> 7 mag）平均为5%。我们还显示了概率分布函数的列密度（N-PDF），这揭示了通常观察到的对数正态分布为低列密度，并表现出在高列密度过剩。作为河外星系研究的参考，我们给出了内星系的视线积分N-PDF，并推导出该过剩对总柱密度的贡献为~ 2.2%，对应于NH 2 = 2.92 × 1022 cm-2。以总通量密度观察到的地图，我们提供了一个独立的估计分子气体的质量在银河系内部的~ 1 × 109？M？，这与先前使用CO排放量的估计一致。从质量和致密气体分数（FDG），我们估计银河系的SFR？= 1.3？M？？yr-1。结论.检索扩展发射有助于更好地识别细长和受限结构的大质量巨丝。我们表明，对数正态分布的低柱密度气体是普遍存在的内星系。虽然扩散气体在银河系内部的分布是相对均匀的，但中心分子区（CMZ）的气体密度较高，尽管它的星星形成效率较低。总之，我们的研究结果很好地解释了银河系ISM中低fDG导致的银河系低星星形成效率。相比之下，高fDG观测到的CMZ，尽管其低星星形成活动，表明，在我们的银河系的特定区域，高密度气体不是星星形成的瓶颈。
Context. Sensitive ground-based submillimeter surveys, such as ATLASGAL, provide a global view on the distribution of cold dense gas in the Galactic plane at up to two-times better angular-resolution compared to recent space-based surveys with Herschel. However, a drawback of ground-based continuum observations is that they intrinsically filter emission, at angular scales larger than a fraction of the field-of-view of the array, when subtracting the sky noise in the data processing. The lost information on the distribution of diffuse emission can be, however, recovered from space-based, all-sky surveys with Planck. Aims. Here we aim to demonstrate how this information can be used to complement ground-based bolometer data and present reprocessed maps of the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) survey. Methods. We use the maps at 353 GHz from the Planck/HFI instrument, which performed a high sensitivity all-sky survey at a frequency close to that of the APEX/LABOCA array, which is centred on 345 GHz. Complementing the ground-based observations with information on larger angular scales, the resulting maps reveal the distribution of cold dust in the inner Galaxy with a larger spatial dynamic range. We visually describe the observed features and assess the global properties of dust distribution. Results. Adding information from large angular scales helps to better identify the global properties of the cold Galactic interstellar medium. To illustrate this, we provide mass estimates from the dust towards the W43 star-forming region and estimate a column density contrast of at least a factor of five between a low intensity halo and the star-forming ridge. We also show examples of elongated structures extending over angular scales of 0.5°, which we refer to as thin giant filaments. Corresponding to > 30 pc structures in projection at a distance of 3 kpc, these dust lanes are very extended and show large aspect ratios. We assess the fraction of dense gas by determining the contribution of the APEX/LABOCA maps to the combined maps, and estimate 2?5% for the dense gas fraction (corresponding to Av> 7 mag) on average in the Galactic plane. We also show probability distribution functions of the column density (N-PDF), which reveal the typically observed log-normal distribution for low column density and exhibit an excess at high column densities. As a reference for extragalactic studies, we show the line-of-sight integrated N-PDF of the inner Galaxy, and derive a contribution of this excess to the total column density of ~ 2.2%, corresponding to NH2 = 2.92 × 1022 cm-2. Taking the total flux density observed in the maps, we provide an independent estimate of the mass of molecular gas in the inner Galaxy of ~ 1 × 109?M?, which is consistent with previous estimates using CO emission. From the mass and dense gas fraction (fDG), we estimate a Galactic SFR of ? = 1.3?M??yr-1. Conclusions. Retrieving the extended emission helps to better identify massive giant filaments which are elongated and confined structures. We show that the log-normal distribution of low column density gas is ubiquitous in the inner Galaxy. While the distribution of diffuse gas is relatively homogenous in the inner Galaxy, the central molecular zone (CMZ) stands out with a higher dense gas fraction despite its low star formation efficiency.Altogether our findings explain well the observed low star formation efficiency of the Milky Way by the low fDG in the Galactic ISM. In contrast, the high fDG observed towards the CMZ, despite its low star formation activity, suggests that, in that particular region of our Galaxy, high density gas is not the bottleneck for star formation.