Star formation in ‘the Brick’: ALMA reveals an active protocluster in the Galactic centre cloud G0.253+0.016
Star formation in ‘the Brick’: ALMA reveals an active protocluster in the Galactic centre cloud G0.253+0.016
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DOI：
10.1093/mnras/stab415
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发表时间：
2021-02
影响因子：
4.8
通讯作者：
D. Walker;S. Longmore;J. Bally;A. Ginsburg;J. M. Diederik Kruijssen-J.-M.-Diederik Kruijssen-2124361283;Qizhou Zhang;J. Henshaw;Xing Lu;J. Alves;A. Barnes;C. Battersby;H. Beuther;Y. Contreras;L. Gomez;L. Ho;J. Jackson;J. Kauffmann;E. Mills;T. Pillai
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文献类型：
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作者：
D. Walker;S. Longmore;J. Bally;A. Ginsburg;J. M. Diederik Kruijssen-J.-M.-Diederik Kruijssen-2124361283;Qizhou Zhang;J. Henshaw;Xing Lu;J. Alves;A. Barnes;C. Battersby;H. Beuther;Y. Contreras;L. Gomez;L. Ho;J. Jackson;J. Kauffmann;E. Mills;T. Pillai
G0.253+0.016，又名“砖”，是银河系中央分子带中质量最大（>105 M⊙）和密度最大（>104 cm−3）的分子云之一。先前的观测发现了活跃恒星形成的初步迹象，最引人注目的是与尘埃连续源有关的水脉泽。我们以0.13角秒（1000天文单位）的角分辨率对这个“脉泽核心”进行了ALMA波段6的观测，并报告了在G0.253+0.016内活跃恒星形成的明确证据。我们检测到18个连续源（中位质量~ 2 M⊙），其中9个通过SiO（5-4）发射驱动双极性分子外流。在水脉泽的位置，我们发现了具有多向流出发射的原恒星双星/多星的证据。尽管G0.253+0.016的密度很高，但我们在ALMA视场中没有发现大质量原恒星的证据。相反，观测到的源与一群低到中等质量的原恒星一致。然而，测量到的流出物性质与中高质量恒星形成的预期一致。我们得出的结论是，这些源是年轻的，正在迅速增加，未来可能会形成中质量和大质量的恒星。核心的质量和投影空间分布与热碎裂基本一致，表明云中的大尺度湍流和强磁场在这些尺度上不占主导地位，单个原恒星的恒星形成与银河系盘环境相似。
G0.253+0.016, aka ‘the Brick’, is one of the most massive (>105 M⊙) and dense (>104 cm−3) molecular clouds in the Milky Way’s Central Molecular Zone. Previous observations have detected tentative signs of active star formation, most notably a water maser that is associated with a dust continuum source. We present ALMA Band 6 observations with an angular resolution of 0.13 arcsec (1000 AU) towards this ‘maser core’ and report unambiguous evidence of active star formation within G0.253+0.016. We detect a population of eighteen continuum sources (median mass ∼2 M⊙), nine of which are driving bi-polar molecular outflows as seen via SiO (5–4) emission. At the location of the water maser, we find evidence for a protostellar binary/multiple with multidirectional outflow emission. Despite the high density of G0.253+0.016, we find no evidence for high-mass protostars in our ALMA field. The observed sources are instead consistent with a cluster of low-to-intermediate-mass protostars. However, the measured outflow properties are consistent with those expected for intermediate-to-high-mass star formation. We conclude that the sources are young and rapidly accreting, and may potentially form intermediate- and high-mass stars in the future. The masses and projected spatial distribution of the cores are generally consistent with thermal fragmentation, suggesting that the large-scale turbulence and strong magnetic field in the cloud do not dominate on these scales, and that star formation on the scale of individual protostars is similar to that in Galactic disc environments.