IRAS 02232+6138的^(13)CO、C^(18)O、HCO^+和N_2H^+的观测研究

Observations Toward IRAS 02232+6138 With ^(13)CO, C^(18)O, HCO^+ and N_2H^+

利用中国科学院紫金山天文台德令哈观测站13．7米望远镜在IRAS 02232+6138方向进行了13CO,C18O,HCO+和N2H+的观测．随着探针分子的激发密度从13CO到N2H+逐渐增加, IRAS02232+6138云核的尺度从13CO的2．40 pc减小到N2H+的0．54pc,云核的维里质量从13CO的2．2×103M⊙减小到N2H+的5．1×102M⊙．研究发现,该方向区域内存在双极分子外流．对云核的空间密度结构用幂函数n(r)αr-α的形式进行拟合分析,得到α=2．3-1．2;随着探测密度的增加,该指数逐渐变平．分析得到, 13CO／C18O分子丰度比值为12．4±6．9,与暗云的11．8±5．9及大质量核的9．0-15．6值一致;N2H+丰度是3．5±2．5×10-10,与暗云核的1．0-5．0×10-10和大质量核的1．2-12．8×10-10值一致;HCO+丰度为0．9±0．5×10-9,接近大质量核的1．6-2．4×10-9值,没有发现HCO+丰度增长．结合IRAS数据,得到云核的光度质量比范围为37-163(L／M)⊙,由IRAS光度估计, IRAS 02232+6138方向云核内嵌埋的大约是一颗主序O7．5星．

Using the Delingha 13.7m millimeter-wave telescope, we observed 13^CO, C^18O, HCO^＋ and N2H^＋ molecular lines toward IRAS 02232＋6138. With the increase of excitation densities from 13^CO to N2H^＋, the sizes of corresponding dense cores associated with IRAS 02232±6138 vary from 2.40 to 0.54 pc and virial masses decrease from 2.2 × 10^3 to 5.1 × 10^2M⊙. A bipolar molecular outflow is found toward IRAS02232＋6138. Using a power-law function of n（r） α r^-α to fit the spatial density structure of the core, we derived power-law indices α= 2.3- 1.2. As critical densities increase from 13^CO to N2H^＋, the power-law function becomes flat gradually. The abundance ratio of 13^CO/C^18O is 12.4±6.9, which is comparable with the ratio of 11.8 ± 5.9 for dark clouds and 9.0 - 15.6 for massive cores. The abundance of N2H^＋ is 3.5 ± 2.5 × 10^-10, which is consistent with the value of 1.0 - 5.0 × 10^-10 for dense cores in dark clouds and 1.2 - 12.8 × 10^-10 for massive cores. The abundance of HCO^＋ is 0.9 ± 0.5 × 10^-9, close to the value of 1.6 - 2.4 × 10^-9 for massive dense cores. No evidence for HCO^＋ enhancement has been observed for this source. In aid of the IRAS data, the luminosity-to-mass ratio of the core was calculated to be in the range of 37 - 163（L/M）⊙. Based on the IRAS luminosity, a young stellar object of spectral type O7.5 has been formed in the IRAS 02232＋6138 core.