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 20231+3440区外流激发源的性质研究

给出红外点源IRAS 20231 3440附近恒星形成区近红外．JHK’和H2成像观测结果，以及与该IRAS点源成协的近红外点源IRS1的K波段分光观测结果．．JHK’观测显示该区域存在嵌埋的年轻星天体，H2窄波段观测揭示了若干个氢分子发射结点，其中有几个结点排列成线形，暗示分子氢喷流的存在．喷流的北部与已知观测的分子外流成协，表明二者之间存在联系．喷流的走向提示IRS1可能是其激发源，对IRS1的K波段分光观测给出了进一步的证据．从近红外、MSX及IRAS资料估计出IRS1的能谱分布，表明它是一个处于ClassI状态的中等质量的年轻星天体．     

和原行星状星云成协的致密反射星云

对从IRAS点源表中选择出来的原行星状星云的光学证认和有缝光谱、CCD直接成像观测表明,其中三个与致密的反射星云成协,即PPN No.34=IRAS16559—2957、PPN No.35=IRAS16552—3050和PPN No.38=IRAS17150—3224。本文根据球对称尘埃壳层模型,计算了中心星光度和颜色的变化,反射星云的可见期等。认为近距的原行星状星云在早中期阶段将有致密的反射星云与它成协。     

星际甲醇分子脉泽的辐射抽运研究

本项研究给出了17个具有Ⅱ类星际甲醇分子脉泽源的致密氢11区的轫致辐射、尘埃红外辐射和中心年轻恒星Layman辐射的特征．以脉泽的光子发射率和辐射亮温度作为两个主要的辐射抽运约束条件，讨论了Ⅱ类星际甲醇分子脉泽的几种可能的激发机制．我们认为热辐射亮温度为100K与致密氢Ⅱ区成协的红外辐射体很可能是Ⅱ类甲醇脉泽的抽运源．     

一个大质量恒星形成复合体的动力学性质

恒星形成于分子云之中, 分子外向流是恒星形成正在进行的重要动力学特征, 也是研究和认识恒星形成的重要契入点. 利用紫金山天文台青海观测站德令哈13.7m毫米波望远镜, 采用5种分子谱线探针(包括¹²CO、¹³CO、C¹⁸O、HCO$^+$ $J=1-0$和CS $J=2-1$, J为角动量量子数), 对一个包含IRAS 19230+1506、IRAS 19232+1504和G050.3179--00.4186这3个源的大质量恒星形成复合体进行了成图观测研究. 通过对以上分子谱线数据并结合红外波段巡天数据的分析, 在这3个源中首次探测到了分子外向流活动, 并确定了分子外向流的中心驱动源. 最后对这3个源进行了分子外向流相关物理量参数的计算, 分析了这些物理量参数之间的关系, 结果表明分子外向流的性质与中心驱动源的性质息息相关.     

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．     

电离氢区S140,S141和S142的红外发射研究

本文使用红外天文卫星（IRAS）巡天数据的最新版本IRAS天空巡天图（ISSA），经过进一步处理，得到了S140S141和S142SharplessHII区－分子云复合体的红外发射强度、温度及其光深的分布．在此基础上对各HII区的一些物理参量进行了统计分析，得到了分子云复合体的红外发射总光度以及复合体中尘埃的分布情况，对小尺度尘埃（VSG）的丰度进行了分析．并对各恒星形成区中的致密团块进行了研究，揭示出其中一些可能的恒星形成区域．同时，对S140区中的有关红外点源作出了能谱分析，并对S141区的激发星进行了讨论．     

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．     

行星状星云NGC 2242的红外辐射

被Zwicky等人列为星系的NGC 2242,后来刘继英等人发现它具有发射特征并认为可能是行星状星云。前原英夫等人用有缝光谱肯定了它是一个行星状星云。我们证认它是IRAS06304+4448。根据IRAS Point Source Catalog所提供的25μm和60μm的辐射流量,我们得到了这一行星状星云的尘埃温度T_d=130K,光学厚度τ_(25μm)=1.98×10~(-7)和尘埃的总质量M_d=1.0×10~(-7)到1.8×10~(-6)M_⊙之间。     

NGC 1333/IRA6-9 区域中的致密分子云核

利用紫金山天文台青海站的13．7m毫米波望远镜,对NGC1333／IRAS6－9附近的一个10．3'X10'和6．8'X8'的恒星形成区,进行了13CO（1－0）和C18O（1－0）的成图观测,发现了多个新的分子云核和沿SSV12－IRASS方向的13CO（1－O）双极外向流．本文给出了每个云核的观测特性和物理参数．分析了这一区域的云核分布和速度场结构．详细讨论了该区域的云核分布、双极外向流和群集的年轻天体、红外源以及HH天体的关系．     

Further observations of IRAS 04302+2247

We present near-infrared broad-band and H₂ images of the quadrupolar source IRAS 04302+2247. High-resolution data at 3.8 μm show that the circumstellar envelope has a high degree of axisymmetry: the asymmetry at shorter wavelengths is almost certainly the result of extinction by dust in the cavity. Photometry of the flux peaks confirms that the source is variable but little change in appearance is observed between 1995 November and 1997 September. We report the first clear detection of the molecular outflow in H₂ at 2.1 μm, revealing discrete streams which are inclined to the axis of the cavity. The motion of knots in the outflow remains the most likely cause of the variability.     

IRAS 01005＋7910：a High Galactic Latitude Post—AGB Star

IRAS 01005＋7910 is a cold IRAS source. We present its optical identification, photometric and spectroscopic observation results. Its optical counterpart is classified as a B2Ie star with V magnitude 10.85. Its Hα line shows the P Cygni profile.According to its location in the Galaxy (b=16.6), we consider it to be a post-AGB star or a proto-planetary nebula.     

Observation and Study of the CO, CO, HCO and N2H Molecular Lines Towards IRAS 02232+6138

Using the 13.7 m millimeter-wave telescope at the Qinghai Station of Purple Mountain Observatory, we have made observations of ¹³CO, C¹⁸O, HCO⁺ and N₂H⁺ molecular lines towards IRAS 02232+6138. As the excitation density of the probe molecule increases from ¹³CO to HCO⁺, the size of the cloud core associated with IRAS 02232+6138 decreases from 2.40 pc to 0.54 pc, and the virial mass of the cloud core decreases from 2.2 × 10³M to 5.1 × 10²M. A bipolar molecular outflow is found towards IRAS 02232+6138. Using the power function n(r) ∝ r⁻ to fit the spatial density structure of the cloud core, we obtain the power-law index  = 2.3 − 1.2; and we find that, as the probed density increases, the power function becomes more flat. The abundance ratio of ¹³CO to C¹⁸O is 12.4 ± 6.9, comparable with the values 11.8 ± 5.9 for dark clouds and the values 9.0–15.6 for massive cores. The abundance of N₂H⁺ molecules is 3.5 ± 2.5 × 10⁻¹⁰, consistent with the value 1.0 − 5.0 × 10⁻¹⁰ for dark cloud cores and the value 1.2 − 12.8 × 10⁻¹⁰ for massive cores. The abundance of HCO⁺ molecules is 0.9 ± 0.5 × 10⁻⁹, close to the value 1.6 − 2.4 × 10⁻⁹ for massive cores. An increase of HCO⁺ abundance in the outflow region was not found. Combining with the IRAS data, the luminosity-mass ratio of the cloud core is obtained in the range 37–163(L/M). Based on the IRAS luminosity, it is estimated that a main-sequence O7.5 star is probably embedded in the IRAS 02232+6138 cloud core.     

The Chemical Classification of the AGB Star IRAS 17515-2407

The chemical classification of IRAS 17515-2407 has been debated for a long time. Up to now there are two contenders, oxygen-rich or carbon-rich. We believe that IRAS 17515-2407 is an oxygen-rich source: because (ⅰ) it shows the silicate self-absorbed emission; (ⅱ) in the near infrared-IRAS diagram it is located in the oxygen-rich object region and (ⅲ) particularly, it has detected SiO maser emission.     

Star-forming region BBW 36 in puppis

Recent studies of the star formation region BBW 36 and associated molecular clouds are presented. The ¹²CO (1-0) observations, carried out with the 15-m SEST (Swedish-ESO) telescope (Cerro La Silla, Chile), revealed the existence of cloud a, connected with BBW 36 and of cloud b, having elongation in SE-NW direction. A red-shifted molecular outflow with velocity ∼+5 km/s (with respect to cloud a), having a direction parallel to the line of sight, was also observed. VLA observations showed the presence of a source VLA 2 at 3.6 cm with an elongation in the N-S direction. It is suggested that the VLA 2 source coincides with a dust disc (surrounding the object BBW 36). The star 3, which is one of the YSOs in the star-forming region BBW 36 and is connected with a bright comma-like nebula, can be the source of the molecular outflow. The star 3 has very high IR colors and is associated with an IRAS point source IRAS 07280-1829, which has IR colors, typical for an IRAS point source, connected with a water maser. On the 2MASS K image of BBW 36 we can see the existence of a bright nebula; a group of stars is embedded in that nebula, and among these stars there are stars with dust discs (or envelopes). On the 2MASS K image several spiral jets are also present, some of them with a condensation at the end. Published in Astrofizika, Vol. 51, No. 3, pp. 469–477 (August 2008).     

About the nature of IRAS 19075+0921

We use infrared data to further investigate the nature of IRAS 19075+0921. Our results indicate that IRAS 19075+0921 is heavily obscured by its thick, circumstellar envelope and possibly composed of two infrared sources all with late spectral types so that it presents a dual chemistry nature.     

NGC 1333/IRAS 4: a multiple star formation laboratory

We present SCUBA observations of the protomultiple system NGC 1333/IRAS 4 at 450 and 850 μm. The 850-μm map shows significant extended emission which is most probably a remnant of the initial cloud core. At 450 μm, the component 4A is seen to have an elongated shape suggestive of a disc. Also we confirm that, in addition to the 4A and 4B system, there exists another component 4C, which appears to lie out of the plane of the system and of the extended emission. Deconvolution of the beam reveals a binary companion to IRAS 4B. Simple considerations of binary dynamics suggest that this triple 4A–4BI–4BII system is unstable and will probably not survive in its current form. Thus IRAS 4 provides evidence that systems can evolve from higher to lower multiplicity as they move towards the main sequence. We construct a map of spectral index from the two wavelengths, and comment on the implications of this for dust evolution and temperature differences across the map. There is evidence that in the region of component 4A the dust has evolved, probably by coagulating into larger or more complex grains. Furthermore, there is evidence from the spectral index maps that dust from this object is being entrained in its associated outflow.     

Star formation in the Cepheus Flare region – II. A-type stars associated with IRAS sources

In order to reveal the star-forming history of the molecular cloud complex we studied the intermediate mass stellar population in the Cepheus Flare region. (Paper I dealt with the distance and the young stellar object candidates of the region.) Correlating the IRAS Point Source Catalogue and Faint Source Catalogue positions with those of 1214 B8–A8 and 1760 F0–F5 type stars brighter than     and classified during an objective prism survey, we identified 19 stars showing far-infrared excess emission in the Cepheus Flare region. In addition to the 16 stars whose counterparts are given in the IRAS catalogues, we found three more stars with infrared excess not recognized before. In order to identify the young medium-mass stars associated with the Cepheus Flare molecular clouds we observed the optical spectra of the IR-excess stars, and using published optical photometry and the IRAS data we examined their spectral energy distributions (SEDs) and IRAS two-colour diagram. The observations resulted in the discovery of a new Herbig Ae/Be star, BD +68°1118, coinciding with IRAS 21169+6842. More evolved HAe/Be stars may be SAO 19953, BD +67°1314 and BD +69°1231, whose H α lines showed weak emission components. Possible β Pictoris- or Vega-type stars may be HD 203854, HD 212826 and HD 216486, whereas the far-infrared fluxes at the positions of BD +72°1018, HD 210806 and HD 217903 can be attributed to the heating of the interstellar environment. We used distances and radial velocities of the stars derived from the spectroscopy and published optical photometry as indicators of their relations to the clouds. Information on the environment of the observed stars deduced from the diffuse interstellar band at λ 6613 is briefly discussed.     

A Search for High-velocity Gas Associated H_2O Masers and Ultracompact HII Regions

1 INTRODUCTIONA violent molecular outflow is a bajsic component of star formation process. Such outflowsare observed over a wide range of wavelength from the ultraviolet to the radio, resulting fromthe interaction of highly supersonic stellar winds with the alnbiellt material and the windejection takes place in the vicinity of a newly formed star. Outflows are produced by starsof all massess but currellt outflow theories are predominantly based on observations of nearby,low-mass outflow sy…