High-Angular Resolution Millimeter-Wave and Near-Infrared Imaging of the Ultracompact H II Region G29.96–0.02
High-Angular Resolution Millimeter-Wave and Near-Infrared Imaging of the Ultracompact H II Region G29.96–0.02
复制标题
超紧凑 H II 区域的高角分辨率毫米波和近红外成像 G29.96–0.02
DOI：
--
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
E. Bergin
中科院分区：
文献类型：
--
作者：
P. Pratap;S. Megeath;E. Bergin
我们提出了一个高角分辨率的彗星状超紧凑H II区域G29.96-0.02的研究。我们用比马干涉仪获得了~（13）CO，C_（18）O，CH_3CN，CH_3OH和CS跃迁区的~10'角分辨毫米波图。我们结合联合收割机这些数据与互补的单碟数据的13 CO，C18 O，和CS线与FCRAO 14米望远镜。这些数据与Calar-Alto 3.5 m望远镜获得的角分辨率≤ 0.9 ″的近红外JHK波段图像进行了比较。13 CO数据显示，发射扩展到3 × 2 pc区域;然而，发射在H II区域的头部附近强烈达到峰值。强烈的CS，C18 O和CH 3CN排放量在同一位置附近达到峰值。CH 3CN（J=6→5）的发射峰朝向之前在VLA NH3（4，4）观测中检测到的热核心，我们使用CH 3CN（6→5）比马数据和CH 3CN/CH 133 CN（5→4）IRAM 30 m望远镜数据的大速度梯度分析确定核心中的动力学温度为100 K。我们还发现，尖锐的峰值C18 O，13 CO，和CS的排放是一个密度梯度的指示，与位于彗星H II区的头部前面的峰值密度。我们使用我们的近红外数据来搜索嵌入在H II区域和邻近云的源。除了令人兴奋的星星的H II区域，我们确定了第二个星星对头部的H II区域的消光类似的令人兴奋的星星，这似乎是第二个OB星星在H II区域。在H II区的正前方，我们探测到一个高度变红的源，它很可能是一颗深深嵌入分子气体中的年轻星星。此外，我们发现了一个增强的源与H-K >1的分子云的密度，并认为这些源形成一个嵌入式集群。最后，我们比较我们的结果与目前的彗星形状的H II地区的模型。鉴于G29.96 H II区域存在于H II区域头部前的分子气体密度梯度中的证据，我们倾向于该区域的香槟流模型。比较测量的密度，温度和线宽的电离和分子气体，我们估计的H II区域的分子核心的膨胀速度在2-5公里s-1。
We present a high-angular resolution study of the cometary-shaped ultracompact H II region G29.96-0.02. We have obtained ~10' angular-resolution millimeter-wave maps of the region in transitions of 13CO, C18O, CH3CN, CH3OH, and CS with the BIMA interferometer. We combine these data with complementary single-dish data of the 13CO, C18O, and CS lines taken with the FCRAO 14 meter telescope. These data are compared with near-infrared JHK-band images with ≤0.″9 angular resolution obtained with the Calar-Alto 3.5 m telescope. The 13CO data show emission extended over a 3 × 2 pc region; however, the emission is strongly peaked near the head of the H II region. Strong CS, C18O, and CH3CN emissions peak near the same location. The CH3CN (J=6→5) emission peaks toward the hot core previously detected in VLA NH3(4, 4) observations, and we determine a kinetic temperature of 100 K in the core using a large velocity gradient analysis of the CH3CN (6→5) BIMA data and CH3CN/CH133CN (5→4) IRAM 30 m telescope data. We also find that the sharply peaked C18O, 13CO, and CS emission is indicative of a density gradient, with the peak density located in front of the head of the cometary H II region. We use our near-infrared data to search for sources embedded in the H II region and the adjacent cloud. In addition to the exciting star of the H II region, we identify a second star toward the head of the H II region with an extinction similar to that of the exciting star; this appears to be a second OB star in the H II region. Directly in front of the H II region we detect a highly reddened source, which is most likely a young star deeply embedded in the molecular gas. Furthermore, we find an enhanced density of sources with H-K >1 toward the molecular cloud and argue that these sources form an embedded cluster. Finally, we compare our results with current models of cometary shaped H II regions. Given the evidence that the G29.96 H II region exists in a gradient of molecular gas density that peaks in front of the head of the H II region, we favor the champagne flow model for this region. Comparing the measured densities, temperatures, and line widths of the ionized and molecular gas, we estimate the expansion speed of the H II region into the molecular core at 2-5 km s-1.