A Photoevaporating Rotating Disk in the Cepheus A HW2 Star Cluster

A Photoevaporating Rotating Disk in the Cepheus A HW2 Star Cluster
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仙王座 HW2 星团中的光蒸发旋转盘

DOI：
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发表时间：
2007
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通讯作者：
P. Schilke
P. Schilke
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作者：
I. Jímenez;J. Martín;A. Rodríguez;C. Chandler;C. Comito;P. Schilke

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我们给出了射电连续辐射在7 mm处的VLA和PdBI亚角秒图像（~ 0.15“-0.6”），以及朝向Cep A HW 2区的SO2 J = 192，18 → 183，15和J = 278，20 → 287，21线的图像。SO2图像揭示了一个由中等质量原恒星内部加热的热核的存在，以及围绕HW 2射电喷流的一个大小为600 × 100 Au、质量约为1 M的星周旋转盘。开普勒旋转的磁盘速度梯度为5公里秒-1需要一个9米的中央星星，这不能解释在该地区观察到的总光度。这可能表明，由于这个物体的极端年轻，圆盘并不按照开普勒定律旋转。我们的高灵敏度无线电连续图像在7毫米显示，除了电离喷流，延长发射到西部（和南部边缘）的HW 2喷流，填充西南腔的HW 2磁盘。从厘米和毫米波长（光谱指数~0.4-1.5）的这种自由-自由连续辐射的形态和位置，我们提出，由于中央星星的紫外线辐射，磁盘是光蒸发。所有这些都表明Cep A HW 2区域拥有一个大质量恒星群。盘吸积似乎是在中等密度/光度的星团中形成大质量恒星的最合理的方式。
We present VLA and PdBI subarcsecond images (~0.15''-0.6'') of the radio continuum emission at 7 mm and of the SO2 J = 192, 18 → 183, 15 and J = 278, 20 → 287, 21 lines toward the Cep A HW2 region. The SO2 images reveal the presence of a hot core internally heated by an intermediate-mass protostar, and a circumstellar rotating disk around the HW2 radio jet of size 600 × 100 AU and mass ~1 M☉. Keplerian rotation for the disk velocity gradient of ~5 km s-1 requires a 9 M☉ central star, which cannot explain the total luminosity observed in the region. This may indicate that the disk does not rotate with a Keplerian law due to the extreme youth of this object. Our high-sensitivity radio continuum image at 7 mm shows, in addition to the ionized jet, an extended emission to the west (and marginally to the south) of the HW2 jet, filling the southwest cavity of the HW2 disk. From the morphology and location of this free-free continuum emission at centimeter and millimeter wavelengths (spectral index ~0.4-1.5), we propose that the disk is photoevaporating due to the UV radiation from the central star. All this indicates that the Cep A HW2 region harbors a cluster of massive stars. Disk accretion seems to be the most plausible way to form massive stars in moderate density/luminosity clusters.