A Census of Early-phase High-mass Star Formation in the Central Molecular Zone
A Census of Early-phase High-mass Star Formation in the Central Molecular Zone
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DOI：
10.3847/1538-4365/ab4258
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发表时间：
2019-09
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影响因子：
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通讯作者：
Xing 行 Lu 吕;E. Mills;A. Ginsburg;D. Walker;A. Barnes;N. Butterfield;J. Henshaw;C. Battersby
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作者：
Xing 行 Lu 吕;E. Mills;A. Ginsburg;D. Walker;A. Barnes;N. Butterfield;J. Henshaw;C. Battersby
我们对银河系中央分子带（CMZ）内部200 pc的C波段连续辐射和脉泽进行了新的观测，以评估在早期演化阶段高质量（>8）星星的形成。连续谱观测在91%的覆盖区域内完成了10-11以上恒星的自由-自由辐射。我们确定了104个致密源的连续发射，其中5个是已确认的超致密H ii区域，12个是超致密H ii区域的候选者，其余87个源大多是大质量恒星的集群，场星，演化的恒星，星系，河外源，或未知的性质，是要调查。我们在23个位置上探测到了II类CH_3OH脉泽，其中6个是新探测到的。我们确认六个已知的H2 CO脉泽在两个高质量的恒星形成区域，并检测到两个新的H2 CO脉泽对Sgr C云，使其成为第九个地区在银河系中，包含这种类型的脉泽。尽管有这些发现，我们发现，目前的高质量星星形成的内部CMZ只发生在七个孤立的云。结果表明，星星的形成在早期的演化阶段中的CMZ是约10倍的效率比预期的致密气体星星形成的关系，这是符合以往的研究，重点是更进化阶段的星星形成。这意味着，如果有任何即将发生的，下一个爆发的星星形成在CMZ，它还没有开始。
We present new observations of the C-band continuum emission and masers to assess high-mass (>8 ) star formation at early evolutionary phases in the inner 200 pc of the Central Molecular Zone (CMZ) of the Galaxy. The continuum observation is complete to free–free emission from stars above 10–11 in 91% of the covered area. We identify 104 compact sources in the continuum emission, among which five are confirmed ultracompact H ii regions, 12 are candidates of ultracompact H ii regions, and the remaining 87 sources are mostly massive stars in clusters, field stars, evolved stars, pulsars, extragalactic sources, or of unknown nature that is to be investigated. We detect class ii CH3OH masers at 23 positions, among which six are new detections. We confirm six known H2CO masers in two high-mass star-forming regions and detect two new H2CO masers toward the Sgr C cloud, making it the ninth region in the Galaxy that contains masers of this type. In spite of these detections, we find that current high-mass star formation in the inner CMZ is only taking place in seven isolated clouds. The results suggest that star formation at early evolutionary phases in the CMZ is about 10 times less efficient than expected from the dense gas star formation relation, which is in line with previous studies that focus on more evolved phases of star formation. This means that if there will be any impending, next burst of star formation in the CMZ, it has not yet begun.