Dual Cometary H II Regions in DR 21: Bow Shocks or Champagne Flows?
Dual Cometary H II Regions in DR 21: Bow Shocks or Champagne Flows?
复制标题
DR 21 中的双彗星 H II 区域：弓形激波还是香槟流？
DOI：
10.1086/377688
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
P. Ho
中科院分区：
文献类型：
--
作者：
C. Cyganowski;M. Reid;V. Fish;P. Ho
DR 21 巨大的恒星形成区域包含两个彗星 H II 区域，在天空上几乎彼此垂直排列。这提供了区分彗星 H II 区域模型的独特机会。我们展示了用甚大阵列对 DR 21 进行的氢复合和氨线观测。从 NH3 发射线和吸收线测得的分子气体速度在整个区域内恒定在 ±1 km s-1 范围内。然而，从氢复合线测得的电离物质的径向速度在两个彗星 H II 区域的“头部”之间相差约 9 km s-1，与分子气体的径向速度相差约 7 km s-1。这些发现表明彗星区域的致密头部之间以及每个头部与周围分子材料之间存在超音速速度差异。这表明，观测到的彗星形态很大程度上是由风吹动的电离恒星穿过分子云的运动造成的，就像弓形激波模型一样。
The DR 21 massive star-forming region contains two cometary H II regions, aligned nearly perpendicular to each other on the sky. This offers a unique opportunity to discriminate among models of cometary H II regions. We present hydrogen recombination and ammonia line observations of DR 21 made with the Very Large Array. The velocity of the molecular gas, measured from NH3 emission and absorption lines, is constant to within ±1 km s-1 across the region. However, the radial velocity of the ionized material, measured from hydrogen recombination lines, differs by ≈9 km s-1 between the "heads" of the two cometary H II regions and by up to ≈7 km s-1 from that of the molecular gas. These findings indicate a supersonic velocity difference between the compact heads of the cometary regions and between each head and the ambient molecular material. This suggests that the observed cometary morphologies are created largely by the motion of wind-blowing, ionizing stars through the molecular cloud, as in a bow shock model.