Star formation in a clustered environment around the UCH II region in IRAS 20293+3952
Star formation in a clustered environment around the UCH II region in IRAS 20293+3952
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IRAS 20293 3952 UCH II 区域周围星团环境中的恒星形成
DOI：
10.1051/0004-6361:20065936
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发表时间：
2007
影响因子：
6.5
通讯作者：
H. Beuther
中科院分区：
文献类型：
--
作者：
A. Palau;R. Estalella;J. Girart;P. Ho;Qizhou Zhang;H. Beuther
目标。我们的目标是研究IRAS 20293+3952中UCH ii区域周围的星团环境，该区域处于高质量星星周围星团形成的第一阶段。方法.用比马和VLA观测了UCH ii区周围的3 mm连续谱、N2 H+（1-0）、NH3（1，1）、NH3（2，2）和CH 3OH（2-1）发射。我们研究了该区域的运动学，并通过拟合N2 H+和NH3的超精细结构计算了旋转温度和柱密度图。结果由N2 H+和NH3追踪的致密气体显示了两种不同的云，一种是UCH ii区域东部的主云，为10.5 pc和10250 M ²，另一种是西部的云，为10.15 pc和1030 M ²。尘埃释放揭示了主云北方的两个强成分，比马1和比马2，与年轻恒星天体（YSO）驱动分子外流有关，以及南部的两个较暗的成分，比马3和比马4，没有星星形成活动的迹象。对于CH 3OH，我们发现了与流出B相关的叉形结构中的强发射，以及与流出A相关的发射。与致密气体有关的YSO似乎具有不同的年龄和性质。旋转温度在主云的北方一侧（约22 K）高于主云的南侧（约16 K），而主云的北侧是YSO最多的地方。该地区有很强的化学分化，因为我们确定的NH3/N2 H+比率，低的值，1050，与YSO在北部的主云，和高的值，高达300，与核心没有检测到YSO，在南部的主云。这种化学差异可能是由于丰度/贫化效应。最后，该区域不同来源之间的互动也很重要。首先，UCH ii区域与主云相互作用，加热它并增强CN（1-0）发射。第二，流出物A似乎正在挖掘一个空腔并加热其壁。第三，外流B与比马4核心相互作用，可能产生外流的偏转，并照亮了位于地震东北方0.2秒差距的一个团块。结论. IRAS 20293+3952中的星星形成过程与相互作用没有明显联系，但似乎发生在密度最高的地方。
Aims. We aim at studying the cluster environment surrounding the UCH ii region in IRAS 20293+3952, a region in the first stages of formation of a cluster around a high-mass star. Methods. BIMA and VLA were used to observe the 3 mm continuum, N2H + (1–0), NH3 (1, 1), NH3 (2, 2), and CH3OH (2–1) emission of the surroundings of the UCH ii region. We studied the kinematics of the region and computed the rotational temperature and column density maps by fitting the hyperfine structure of N2H + and NH3. Results. The dense gas traced by N2H + and NH3 shows two different clouds, a main cloud to the east of the UCH ii region, of ∼0.5 pc and ∼250 M� , and a western cloud, of ∼0.15 pc and ∼30 M� . The dust emission reveals two strong components in the northern side of the main cloud, BIMA 1 and BIMA 2, associated with Young Stellar Objects (YSOs) driving molecular outflows, and two fainter components in the southern side, BIMA 3 and BIMA 4, with no signs of star forming activity. Regarding the CH3OH, we found strong emission in a fork-like structure associated with outflow B, as well as emission associated with outflow A. The YSOs associated with the dense gas seem to have a diversity of age and properties. The rotational temperature is higher in the northern side of the main cloud, around 22 K, where there are most of the YSOs, than in the southern side, around 16 K. There is strong chemical differentiation in the region, since we determined low values of the NH3/N2H + ratio, ∼50, associated with YSOs in the north of the main cloud, and high values, up to 300, associated with cores with no detected YSOs, in the south of the main cloud. Such a chemical differentiation is likely due to abundance/depletion effects. Finally, interaction between the different sources in the region is important. First, the UCH ii region is interacting with the main cloud, heating it and enhancing the CN (1–0) emission. Second, outflow A seems to be excavating a cavity and heating its walls. Third, outflow B is interacting with the BIMA 4 core, likely producing the deflection of the outflow and illuminating a clump located ∼0.2 pc to the northeast of the shock. Conclusions. The star formation process in IRAS 20293+3952 is not obviously associated with interactions, but seems to take place where density is highest.