分子云G35 .20 $-$ 0.74中的恒星形成活动：云-云碰撞的开始
Star Formation Activity in the molecular cloud G35.20$-$0.74: onset of cloud-cloud collision
摘要：
为了探测恒星形成过程，我们利用多频观测对分子云G35.20 $-$ 0.74（以下简称MCG 35.2）进行了分析。MCG 35.2的速度范围为30-40 km s $^{-1}$。嵌入MCG 35.2内的几乎马蹄形结构在红外和毫米图像中是明显的，并且在其底部具有先前已知的位点，超紧凑/超紧凑G35.20 $-$ 0.74 N H\，{ \sc ii}区域，Ap 2 -1和Mercer 14。发现该站点Ap 2 -1是由射电光谱类型为B0.5V的恒星激发的，其中20 cm和H $α$发射的分布被扩展的分子氢发射所包围。利用{ \it Herschel} 160-500 $μ$ m和测光1-24 $μ$ m的数据分析，研究了MCG 35.2中的几个年轻恒星天体（YSO）团簇，揭示了SF活动。大多数的YSO星团和大质量的团块（500-4250 M $_{\odot}$）都朝向马蹄形结构。对$^{13}$ CO辐射的位置-速度分析表明，在33 km/s $^{-1}$处有一个蓝移峰，在37 km/s $^{-1}$处有一个红移峰，它们之间由较低强度的中速辐射相互连接，具有宽桥特征。这种宽桥特征的存在表明MCG35.2中分子组分之间的碰撞开始。在MCG35.2中也观察到H波段星光平均偏振角的显著变化，可能是分子组分之间相互作用的结果。总的来说，云-云碰撞过程似乎影响了MCG35.2中大质量恒星和YSO星团的诞生。
英文摘要：
To probe the star-formation (SF) processes, we present results of an analysis of the molecular cloud G35.20$-$0.74 (hereafter MCG35.2) using multi-frequency observations. The MCG35.2 is depicted in a velocity range of 30-40 km s$^{-1}$. An almost horseshoe-like structure embedded within the MCG35.2 is evident in the infrared and millimeter images and harbors the previously known sites, ultra-compact/hyper-compact G35.20$-$0.74N H\,{\sc ii} region, Ap2-1, and Mercer 14 at its base. The site, Ap2-1 is found to be excited by a radio spectral type of B0.5V star where the distribution of 20 cm and H$α$ emission is surrounded by the extended molecular hydrogen emission. Using the {\it Herschel} 160-500 $μ$m and photometric 1-24 $μ$m data analysis, several embedded clumps and clusters of young stellar objects (YSOs) are investigated within the MCG35.2, revealing the SF activities. Majority of the YSOs clusters and massive clumps (500-4250 M$_{\odot}$) are seen toward the horseshoe-like structure. The position-velocity analysis of $^{13}$CO emission shows a blue-shifted peak (at 33 km s$^{-1}$) and a red-shifted peak (at 37 km s$^{-1}$) interconnected by lower intensity intermediated velocity emission, tracing a broad bridge feature. The presence of such broad bridge feature suggests the onset of a collision between molecular components in the MCG35.2. A noticeable change in the H-band starlight mean polarization angles has also been observed in the MCG35.2, probably tracing the interaction between molecular components. Taken together, it seems that the cloud-cloud collision process has influenced the birth of massive stars and YSOs clusters in the MCG35.2.
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