The evolutionary status of protostellar clumps hosting class II methanol masers
The evolutionary status of protostellar clumps hosting class II methanol masers
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DOI：
10.1093/mnras/staa233
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发表时间：
2020-01
影响因子：
4.8
通讯作者：
BM Jones;G. Fuller;Shari Breen;A. Avison;J. Green;A. Traficante;D. Elia;S. Ellingsen;M. Voronkov;M. Merello;M. Merello;S. Molinari;E. Schisano
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文献类型：
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作者：
BM Jones;G. Fuller;Shari Breen;A. Avison;J. Green;A. Traficante;D. Elia;S. Ellingsen;M. Voronkov;M. Merello;M. Merello;S. Molinari;E. Schisano
甲醇多波束巡天 (MMB) 提供了拥有 6.7 GHz II 类甲醇微波激射器的银河系大质量年轻恒星物体 (MYSO) 最完整的样本。我们利用赫歇尔红外银河平面巡天（Hi-GAL）检测到的尘埃发射来表征这些微波激射源的特性，以评估它们的演化状态。将 731 个（73%）MMB 源与四个 Hi-GAL 波长的紧凑发射相关联，我们得出了簇属性并定义了 MYSO 承载 6.7 GHz 微波激射器的要求。对于银心近侧的源，远红外 (FIR) 质量和光度中值分别为 630 M⊙ 和 2500 L⊙，对于更远的源，中值远红外 (FIR) 质量和光度为 3200 M⊙ 和 10000 L⊙。两者在~4.2 L⊙ M⊙-1 处的中值光度与质量比相似。我们确定了维持给定光度的甲醇微波激射器所需的表观最小 70 μm 光度（L70 ∝ L6.70.6）。与一般银河系原恒星 MYSO 群体相比，脉泽宿主团块具有更高的质量和更高的远红外光度。通过主成分分析，我们发现 896 个原恒星团块满足承载甲醇微波激射器的要求，但在 MMB 中缺乏检测。在这些物体中发现 70 μm 通量密度不足，我们赞成这些物体进化到超过可以维持发光的 6.7 GHz 微波激射器的年龄的情况。最后，通过与次要微波激射器物种相关的分离确定了 6.7GHz 源群体内的进化差异。
The Methanol MultiBeam survey (MMB) provides the most complete sample of Galactic massive young stellar objects (MYSOs) hosting 6.7 GHz class II methanol masers. We characterize the properties of these maser sources using dust emission detected by the Herschel Infrared Galactic Plane Survey (Hi-GAL) to assess their evolutionary state. Associating 731 (73 per cent) of MMB sources with compact emission at four Hi-GAL wavelengths, we derive clump properties and define the requirements of an MYSO to host a 6.7 GHz maser. The median far-infrared (FIR) mass and luminosity are 630 M⊙ and 2500 L⊙ for sources on the near side of Galactic centre and 3200 M⊙ and 10000 L⊙ for more distant sources. The median luminosity-to-mass ratio is similar for both at ∼4.2 L⊙ M⊙-1. We identify an apparent minimum 70 μm luminosity required to sustain a methanol maser of a given luminosity (with L70 ∝ L6.70.6). The maser host clumps have higher mass and higher FIR luminosities than the general Galactic population of protostellar MYSOs. Using principal component analysis, we find 896 protostellar clumps satisfy the requirements to host a methanol maser but lack a detection in the MMB. Finding a 70 μm flux density deficiency in these objects, we favour the scenario in which these objects are evolved beyond the age where a luminous 6.7 GHz maser can be sustained. Finally, segregation by association with secondary maser species identifies evolutionary differences within the population of 6.7GHz sources.