分子云中的甲醛1_(10)—1_(11)和2_(11)—2_(12)跃迁谱线——气体密度和甲醛丰度的确定

Formaldehyde 1_(10)-l_(11) and 2_(11)-2(12) Transitions in Molecular Clouds—— Gas Densities and H,CO Abundance

对分子云中甲醛的辐射传能问题用大速度梯度模型进行了分析和计算,以图解形式表示出气体温度为10K,20K,40K及70K的计算结果。表明在相似分辨率下的H_2CO 1_(10)—1_(11)和2_(11)—2_(12)谱线观测可以确定分子云中的气体密度和甲醛丰度。在20K—100K范围内,结果对气体温度的依赖并不十分强。 确定了Cirrus 7核区的某些物理参数。考虑到周围低密度气体的压力,用维里定理考察了此核区的稳定性,发现它是引力束缚的,可能处于动力学平衡状态,也可能坍缩形成低质量恒星。

The radiative transfer on foemaldehyde in molecular clouds is analyzed and calculated by using a large velocity gradient model. The results for gas temperatures 10K, 20K, 40K and 70K are presented schematically. It is shown that the observations of H2COl10-111 and 211-212 transitions at a similar resolution can be used to estimate the gas density and HaCO fractional abundance in molecular clouds. In the range of gas temperature 20K to 100K the results are not very sensitive to gas temperature.Some physical parameters of the core of Cirrus cloud 7 are estimated. Gravitational stability of the core is investigated by using the virial theorem, taking into account the pressure of the surrounding low dense 'helo'. It is found that the core is gravitationally bound and it is possible that the core is in the dynamical equilibrium or collapses to form a low mass star.