正在形成恒星的孤立分子云核物理性质的观测研究  

An Observational Study of Physical Properties towards Star-forming Molecular Cores

作　　者：李波[1] 裴春传[1] 马红君[1] 

机构地区：[1]中国科学院紫金山天文台,南京210008

出　　处：《天文学报》2007年第2期139-152,共14页Acta Astronomica Sinica

基　　金：国家自然科学基金项目(10373025)资助

摘　　要：利用青海站13．7m毫米波望远镜对从Spitzer的c2d项目样本中挑选出来的11个内部有恒星正在形成的孤立分子云核进行了13CO(J=1-0)、13CO(J=1-0)和C18O(J=1-0)的同时成图观测．对这些分子云核均观测到13CO(J=1-0)峰值强度极大值的一半处．计算了分子云核的密度和质量,得到维里质量(MVIR)与LTE质量(MLTE)之比13CO(J=1-0)为0．85±0．40,C18O(J=1-0)为0．77±0．35．同时计算了云核的密度轮廓．The data of （J = 1 - 0） lines of 12^CO,13^CO and C^18O were taken simultaneously by using 13.7m millimeter telescope of Qinghai station of Purple Mountain Observatory at Delingha. The mapped 11 isolated star-forming molecular cores were selected from Spitzer＇s c2d Legacy program. The maps for one source cover the same range, at the boundary the intensity of 13^CO（J = 1 - 0） equals its half peak value. The optical depth, excitation temperature and column density are calculated. The volume density, local thermodynamic equilibrium（LTE）-mass （MLTE） and Virial-mass（MviR） are derived for each core. The ratio of MVIR to MLTE is 0.84 ± 0.38 for 13^CO（J = 1 - 0） cores and 0.76 ± 0.32 for C^18O（J = 1 - 0） cores. In the most of the cores, the intensities of 13^CO（J = 1 - 0） lines are equal to or even lower than that of ClSo（J = 1 - 0） lines because of the self-absorption of 13^CO（J = 1 - 0） lines. The asymmetrical spectra of L723, L778, L1152, L1082A and L1165 show that the cores are collapsing and are in the very early stage of star formation. We estimate the density profiles for most of the cores except CB224 and CB230 for unavailable C^18O（J = 1-0） data. The density profile is about γ^-1.3 with the index of 1.3, which is smaller than 2 for the theoretical value. The correlation between the luminosity values and the masses of the cores shows that these cores are at a similar stage of star formation. The ratio of LIR/MLTE is 0.04 for 13^CO（J = 1 - 0） and 0.12 for CISO（J = 1 - 0） while it is typically 4 for massive star forming region. This is probably because that 13^CO（J = 1 - 0） and C^18O（j = 1 - 0） are not ideal dense molecular tracers, and the cores defined by them are larger than the real star forming regions.

关 键 词：恒星 形成 星际介质 谱线和谱带 星际介质 丰度 

分 类 号：P152[天文地球—天文学]