新单极高速分子外向流源IRAS19282+1814

^12CoJ=1-0成图观测表明在IRAS19282 1814附近存在着一个蓝向单极高速分子外流，计算了其基本参量并进行了分析，它的成协红外源IRAS19282 1814可能是大质量年轻星体，其IRAS波段色指数表明该源深埋于气体和尘埃物质之中，由60-100μm流量密度获得尘埃温度为30K,它的附近没有其他的源，所以IRAS19282 1814可能是外向流的驱动源。     

红外源IRAS 05437-0001和IRAS 05351+3549的CO分子谱线观测研究

利用紫金山天文台青海观测站13.7米射电望远镜对红外源IRAS05437-0001和IRAS05351+3549附近区域进行了CO(J=1-0)的分子谱线观测.发现在这两个源的方向都有很强的CO发射,CO谱线还有明显的线翼成分,这暗示两个红外源存在分子外流.同时还获得了每个源5＇×5＇的成图.通过对高速气体的空间分布的观测和分析,认为这两个源为分子外流源.其中IRAS05437-0001附近区域的外流结构比较复杂,可能这一区域的外流是多极的.IRAS05351+3549附近的外流结构较简单.从两个源的红外光谱分类以及外流的动力学时标得出都是年轻星(年龄～105yrs).通过对这两个外流源的参数估算,得出两个外流源的质量损失率.     

IRAS 23133+6050云核的观测研究

利用紫金山天文台青海观测站13.7 m毫米波望远镜对IRAS 23133 6050云核进行~(13)CO、C~(18)O、HCO (J=1-0)谱线观测.~(13)CO、C~(18)O、HCO 分子谱线辐射所对应的云核直径分别为4.0pc、2.1 pc、2.3 pc,质量分别为2.7×10~3M_⊙、0.9×10~3M_⊙、2.3×10~3M_⊙,气体平均密度分别为2.7×10~3 cm~(-3)、5.1×10~3 cm~(-3)、4.6×10~3cm~(-3).用幂律模型n(r)～~(-P)的形式分析了云核的密度分布,得到的指数p分别为1.75、1.56、1.48.分析发现,密度结构谱指数从云核的外部向内部逐渐变平坦.观测得到HCO~ 丰度为4.6×10~(-10),比暗云低一个数量级以上,比巨分子云也略低,而~(13)CO、C~(18)O的相对丰度比X_(13/18)为12.2,这与暗云11.8和巨分子云9.0～15.6的情况一致.该区域发现存在~(13)CO双极外流.由IRAS远红外光度和维里质量得到的光度质量比,分别为18.1,51.1、21.2.     

IRAS05391—0217和IRAS06572—0742源的热动性质

利用紫金山天文台青海观测站１３．７米射电望远镜对源ＩＲＡＳ０５３９１０２１７和ＩＲＡＳ０６５７２０７４２进行了１２ＣＯＪ＝１－０观测,获得了气体的相应参数;用ＩＲＡＳ及其他红外观测资料,获得了尘埃热结构;探讨了云中气体的热平衡．对于ＩＲＡＳ０５３９１０２１７中由远红外得出的Ｔｄ＜Ｔｋ的情形,考虑了几种可能的加热机制．光电加热对该云可能是比较重要的;激波可能是另一种加热途径．     

IRAS 02232+6138的13CO、C18O、HCO+和N2H+的观测研究

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．     

大质量恒星形成的观测和研究

对于大质量的形成，由于区域的遥远和结构的复杂以及过程的特殊，研究相对迟缓，对可能形成大质量得的云核和大质量年轻星体的活动，进行多波段搜寻和研究，取得了相应的进展。     

恒星形成区的云核和星团

利用青海站13.7 m毫米波望远镜对17个与星团成协的恒星形成区进行了~(12)CO(J=1-0)、~(13)CO(J=1-0)和C~(18)O(J=1-0)的同时成图观测.除了IRAS04547+4753,这些源均探测到较强的C~(18)O(J=1-0)的谱线发射.由于分子云的大小不同,有13个源观测到~(13)CO(J=1-0)谱线积分强度极大值的一半处,其他源因分子云延展范围较大,没有进行大面积的成图观测.基于观测数据,计算了各云核的谱线线宽、亮温度、尺度、密度和质量等,~(13)CO和C~(13)O云核的维里质量与局部热动平衡(LTE)质量之比分别为0.66和0.74,它们接近于维里平衡状态.为了从形态方面比较云核与星团,将谱线的积分强度图与2MASS的K波段图像叠加.同时,计算了与云核成协的星团的大小和质量,数据采用了2MASS的近红外点源测光结果.基于云核与星团的质量结果,计算了分子云的恒星形成效率,大致在10%～30%的范围.     

红外暗云中分子气体团块的性质研究

利用¹²CO(1-0)、¹³CO(1-0)与C¹⁸O(1-0)分子谱线成图观测数据,并结合ATLASGAL (The APEX(Atacama Pathfinder Experiment) Telescope Large Area Survey of the Galaxy)尘埃连续谱巡天观测结果详细地研究了9个红外暗云(Infrared Dark Clouds, IRDCs)中团块的物理性质与运动学特征.给出了红外暗云的速度区间,以及在红外暗云所对应的Spitzer (Spitzer Space Telescope) 8μm辐射背景上叠加了与红外暗云轮廓基本吻合的¹³CO和C¹⁸O积分强度分布图. 9个红外暗云中有8个呈纤维状结构.在这些红外暗云中共找出51个致密团块,质量偏大的团块大部分聚集在红外暗云的枢纽位置.质量统计直方图中表现出明显的双峰结构,进一步证实纤维状分子云物质输送的图景.¹²CO(1-0)计算所得的典型激发温度T_ex...     

正在形成恒星的孤立分子云核物理性质的观测研究

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．     

对59个北天EGO天体方向上的分子云~(12)COJ=2-1和J=3-2频谱观测研究

为了研究有大质量恒星形成的分子云与其它分子云之间的差异,对北天的59个作为大质量恒星形成区的Spitzer延展绿色天体(Extended Green Objects,简称EGOs)视线方向进行了分子云~(12)CO J=2-1和J=3-2频谱观测,并与文献中对同一批天体方向观测得到的~(12)CO J=1-0频谱数据合并进行分析.对与EGO天体成协的分子云(简称EGO分子云)和其它non-EGO分子云进行了CO多跃迁谱线强度和宽度的统计比较分析.在数据统计的基础上,讨论了这两类分子云的气体温度分布、密度分布、速度场分布对观测数据统计特征的影响.分析结果表明,直接决定是否有大质量恒星形成的关键因素可能并不是巨分子云的质量是否足够大,而是巨分子云的引力塌缩程度足否充分(即分子云团块的体积填充因子是否足够大).     

Near-Infrared Observations of the Massive Star Forming Region IRAS 23151＋5912

Near-infrared images and K-band spectroscopy of the massive star-forming region IRAS 23151+5912 are presented. The JHK' images reveal an embed-ded infrared cluster associated with infrared nebula, and the H_2 (2.12μm) narrow-band image provides for the first time evidence of outflow activity associated withthe cluster. That the cluster is young can be shown by the high percentage ofinfrared excess sources and the outflow activity. We suggest an age of the clus-ter of ～ 10~6yr. Eight young stars are found in the bright nebular core aroundIRAS 23151+5912. By the color-magnitude diagrams of the cluster, we found fivehigh--mass YSOs and four intermediate-mass YSOs in the cluster. Eight H_2 emissionfeatures are discovered in the region with a scattered and non-axisymmetric distri-bution, indicating the existence of multiple outflows driven by the cluster. DiffuseH_2 emission detected to the north and to the west of the cluster may result fromUV leakage of the cluster. Brγ, H_2, and CIV emission lines are     

Detection of CO Outflow in Rotating Cores

We investigate the effect of bulk motion on the detection of molecular outflows in the sources S 146, GGD27, and IRAS 22566 5830. The traditional techniques do allow for bulk motions or systematic VLSR shifts of the core emissions, which may cause contamination of the high velocity gas emissions, and outflows may either fail to be detected or have their properties miscalculated. We used a program to follow the systematic shift of VLSR and better results have been obtained.     

Properties of the infrared dark cloud G79.2+0.38

The MSX infrared dark cloud G79.2+0.38 has been observed over a 11′×′ region simultaneously in the J=1-0 rotational transition lines of the ¹²CO and its isotopic molecules ¹³CO and ¹⁸CO. The dense molecular cores defined by the C¹⁸O line are found to be associated with the two high-extinction patches shown in the MSX A-band image. The two dense cores have the column density N (H₂) (5 – 12) × 10²² cm⁻² and the mean number density n (3 ± 1) × 10⁴ cm⁻³. Their sizes are 1.7 and 1.2 pc in ¹³CO(1-0) line, 1.2 and 0.6 pc in C¹⁸O(1-0) line, respectively. The masses of these cloud cores are estimated to be in the range from 2 × 10² to 2 × 10³ M. The profile of radial mean density of the cloud core can be described by the exponential function ¯n(p) p^{−0.34±0.02}. Compared with the cases of typical optical dark clouds, the abundances of the CO isotopic molecules ¹³CO and C¹⁸O in this MSX infrared dark cloud appear to be depleted by a factor of 4–11, but at present there is no evidence for any obvious variation of the relative abundance ratio X_13/18 between ¹³CO and C¹⁸O with the column density.     

红外暗云G79.2+0.38的性质

对MSX红外暗云G79.2+0.38的11'×7'的区域范围进行了12CO(1-0)、13CO(1-0)和C18O(1-0)谱线的同时观测.观测到的两个C18O(1-0)谱线所界定的云核峰值分布分别对应MSX A波段的两块高消光区域.该区域的氢分子柱密度N(H2)-(5-12)×1022 cm-2,平均密度n-(3±1)×104cm-3.两块分子云核的13CO的线尺度分别是1.7和1.2 pc,而C18O的线尺度分别是1.2和0.6 pc,它们包含的质量为2×102-2×103M(?).分子云核的视向平均密度结构可用幂函数(?)(p)-p-0.34±0.02表征. 13CO和C18O的丰度和典型的光学暗云相比低了4至11倍,但是目前还没有证据表明13CO和C18O的相对丰度比X13/18随柱密度有显著变化.     

On the detection of artefacts in spectro-astrometry

We demonstrate that artificial bipolar structure can be detected using spectro-astrometry when the point spread function (PSF) of a point source suffers distortion in a relatively wide slit. Spectro-astrometry is a technique which allows us to probe the spatial structure of astronomical sources on milliarcsec (mas) scales making it possible to detect close binaries and to study the geometry and kinematics of outflowing gas on scales much smaller than the seeing or the diffraction limit of the telescope. It is demonstrated that a distorted PSF, caused by tracking errors of the telescope or unstable active optics during an exposure, can induce artificial signals which may be misinterpreted as a real spectro-astrometric signal. Using simulations, we show that these may be minimized by using a narrow slit relative to the seeing. Spectra should be obtained at antiparallel slit position angles (e.g. 0° and 180°) for comparison in order to allow artificial signatures to be identified.     

An Observational Study of the Molecular Cloud Core Toward IRAS 23133+6050

This paper reports ¹³CO, C¹⁸O, HCO⁺ (J = 1−0) spectral observations toward IRAS 23133+6050 with the 13.7 m millimeter-wave telescope at Qinghai Station of PMO. Corresponding to the ¹³CO, C¹⁸O, HCO⁺ line emissions, the size of the observed molecular cloud core is 4.0 pc, 2.1 pc and 2.3 pc, the virial mass is 2.7 × 10³ M_⊙, 0.9 × 10³ M_⊙ and 2.3 × 10³ M_⊙, and the volume density of H₂ is 2.7 × 10³ cm⁻³, 5.1 × 10³ cm⁻³ and 4.6 × 10³ cm⁻³, respectively. Using the power-law function n(r) ∼r^−p, the spatial density distribution of the cloud core was analyzed, the obtained exponent p is respectively 1.75, 1.56 and 1.48 for the ¹³CO, C¹⁸O and HCO⁺ cores, and it is found that the density distribution becomes gradually flatter from the outer region to the inner region of the core. The HCO⁺ abundance is 4.6 × 10⁻¹⁰, one order of magnitude less than the value for dark clouds, and slightly less than that for giant molecular clouds. The ¹³CO/C¹⁸O relative abundance ratio is 12.2, comparable with the value 11.8 for dark clouds, and the value 9.0 ∼ 15.6 for giant molecular clouds. A ¹³CO bipolar outflow is found in this region. The IRAS far-infrared luminosity and the virial masses give the luminosity-mass ratios 18.1, 51.1 and 21.2 from the three lines.     

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

We used the 13.7 m millimeter-wave telescope of the Qinghai Station of Purple Mountain Observatory at Delingha to carry out simultaneous mapping observations in the ¹²CO(J = 1 − 0), ¹³CO(J = 1 − 0) and CO¹⁸ (J = 1 − 0) lines towards 11 isolated star-forming molecular cores selected from the sample of Spitzer's c2d program. For all three lines, these sources were all observed to the positions of half the peak intensity of the ¹³CO(J = 1 − 0) line. The volume density, local thermodynamic equilibrium mass M_LTE and virial mass M_VIR were derived for each of the molecular cores. The obtained ratio of M_VIR to M_LTE is 0.85 ± 0.40 for the ¹³CO(J = 1 − 0) cores and 0.77 ± 0.35 for the CO¹⁸ (J = 1 − 0) cores. The density profiles of the cloud cores were also calculated.