DEEP VERY LARGE ARRAY RADIO CONTINUUM SURVEYS OF GLIMPSE EXTENDED GREEN OBJECTS (EGOs)
DEEP VERY LARGE ARRAY RADIO CONTINUUM SURVEYS OF GLIMPSE EXTENDED GREEN OBJECTS (EGOs)
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DOI：
10.1088/0004-637x/743/1/56
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发表时间：
2011-09
期刊：
影响因子：
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通讯作者：
C. Cyganowski;C. Brogan;T. Hunter;E. Churchwell
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文献类型：
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作者：
C. Cyganowski;C. Brogan;T. Hunter;E. Churchwell
我们介绍了对14个GLIMPSE扩展绿色天体（ego）样本进行的深、高角分辨率甚大阵列射电连续发射巡天的结果。根据斯皮策望远镜的4.5 μm辐射，我们的调查样本中的ego被确定为大质量年轻恒星物体（MYSO）流出候选者，它们也与6.7 GHz II类和/或44 GHz I类CH3OH脉泽有关。在大多数目标（57%）的3.6或1.3 cm处没有检测到连续体（中位数rms ~ 0.03和0.25 mJy beam - 1）。只有两个ego与光学薄发射相关联，与超紧凑/紧凑H ii区一致。这两个源都表现出cm -λ多重性，有证据表明其中一个进化程度较低的成员可能驱动了4.5 μm的流出。大多数cm -λ EGO对应体是弱的（小于1 mJy），无法解析，在1.3 cm处未被探测到，并且具有与超致密（HC） H ii区或电离风或喷流一致的中间光谱指数。一个EGO厘米（cm）的对应，可能是一个光学厚度的HC H ii区域，仅在1.3厘米处被检测到，并且与热核线发射和H2O和6.7 GHz CH3OH微波激射有关。我们异常敏感的调查结果表明，ego表明了大质量恒星形成的早期阶段，在中央MYSO的光电离反馈显著影响（原始）星团环境之前。被调查的ego积极推动流出（因此，可能是积极的吸积），与重要的块状气藏有关，为持续快速的吸积提供了足够的物质。
We present the results of deep, high angular resolution Very Large Array surveys for radio continuum emission toward a sample of 14 GLIMPSE Extended Green Objects (EGOs). Identified as massive young stellar object (MYSO) outflow candidates based on their extended 4.5 μm emission in Spitzer images, the EGOs in our survey sample are also associated with 6.7 GHz Class II and/or 44 GHz Class I CH3OH masers. No continuum is detected at 3.6 or 1.3 cm toward the majority (57%) of our targets (median rms ∼0.03 and 0.25 mJy beam−1). Only two EGOs are associated with optically thin emission consistent with ultracompact/compact H ii regions. Both of these sources exhibit cm–λ multiplicity, with evidence that one of the less-evolved members may be driving the 4.5 μm outflow. Most of the other cm–λ EGO counterparts are weak (≲1 mJy), unresolved, undetected at 1.3 cm, and characterized by intermediate spectral indices consistent with hypercompact (HC) H ii regions or ionized winds or jets. One EGO centimeter (cm) counterpart, likely an optically thick HC H ii region, is detected only at 1.3 cm and is associated with hot core line emission and H2O and 6.7 GHz CH3OH masers. The results of our exceptionally sensitive survey indicate that EGOs signify an early stage of massive star formation, before photoionizing feedback from the central MYSO significantly influences the (proto)cluster environment. Actively driving outflows (and so, presumably, actively accreting), the surveyed EGOs are associated with significant clump-scale gas reservoirs, providing sufficient material for sustained, rapid accretion.