A Remark on Using Gravitational Lensing Probability as a Probe of the Central Regions of CDM Halos     

YunLiNational Astronomical Observatories  Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2002,2(5):399-407

We calculate the gravitational lensing probabilities by cold dark matter (CDM) halos with different density profiles, and compare them with current observations from the Cosmic Lens All-Sky Survey (CLASS) and the Jodrell-Bank VLA Astrometric Survey (JVAS). We find that the lensing probability is dramatically sensitive to the clumping of the dark matter, or quantitatively, the concentration parameter. We also find that our predicted lensing probabilities in most cases show inconsistency with the observations. It is argued that high lensing probability may not be an effective tool for probing the statistical properties of inner structures of dark matter halos.  相似文献   

A Catalog of Luminous Infrared Galaxies in the IRAS Survey and Second Data Release of SDSS     

Chen Cao  Hong Wu  Jian-Ling Wang  Cai-Na Hao  Zu-Gan Deng  Xiao-Yang Xia  Zhen-Long Zou National Astronomical Observatories  Chinese Academy of Sciences  Beijing  Graduate School of Chinese Academy of Sciences  Beijing College of Physical Sciences  Graduate School of Chinese Academy of Sciences  Beijing Department of Physics  Tianjin Normal University  Tianjin 《中国天文和天体物理学报》2006,6(2):197-209

We selected a sample of luminous infrared galaxies by cross-identification of the Faint Source Catalogue (FSC) and Point Source Catalogue (PSC) of the IRAS Survey with the Second Data Release of the SDSS. The size of our sample is 1267 for FSC and 427 for PSC by using the 2σ significance level cross-section. The "likelihood ratio" method is used to estimate the individual's reliability and for defining two more reliable subsamples (908 for FSC and 356 for PSC). A catalog of infrared, optical and radio data is compiled and will be used in further work. Some statistical results show that luminous infrared galaxies are quite different from ultra-luminous infrared galaxies. The AGN fractions of galaxies at different infrared luminosities and the radio-infrared correlations are consistent with the previous studies.  相似文献   

The Relationship between the Rise Width and the Full Width of γ-ray Burst Pulses and Its Implications     

Rui-Jing Lu  Yi-Ping Qin  Ting-Feng Yi 《中国天文和天体物理学报》2006,6(1)

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A Two—Temperature Supernova Fallback Disk Model for Anomalous X—ray Pulsars     

Ye Lu  K. S. Cheng National Astronomical Observatories  Chinese Academy of Sciences  Beijing Department of Physics  University of Hong Kong  Hong Kong  China 《中国天文和天体物理学报》2002,2(2):161-168

We present a case study of the relevance of the radially pulsational instability of a two-temperature accretion disk around a neutron star to anomalous X-ray pulsars (AXPs). Our estimates are based on the approximation that such a neutron star disk with mass in the range of 10^-6-10^-5M⊙ is formed by supernova fallback. We derive several peculiar properties of the accretion disk instability: a narrow interval of X-ray pulse periods; lower X-ray luminosities; a period derivative and an evolution time scale. All these results are in good agreement with the observations of the AXPs.  相似文献   

Properties of OH Megamaser Galaxies in the Radio Continuum. II. Data Analysis     

R. A. Kandalyan 《Astrophysics》2005,48(2):237-243

The properties of OH megamaser galaxies in the radio continuum are discussed. Many radio sources in OH megamaser galaxies exhibit relatively flat (α ≥ −0.5) radio spectra between frequencies of 1.49 and 8.44 GHz along with high brightness temperatures (T_b ≥ 10⁴ K). In these galaxies the line and radio continuum fluxes are not correlated. The continuum radio emission of OH megamasers is predominantly nonthermal and is associated either with an active nucleus or with compact star formation. The thermal component of the radio emission from these galaxies can be neglected. The observed flat radio spectra and high brightness temperatures imply the existence of an active galactic nucleus, although some megamasers may be associated with compact star formation.__________Translated from Astrofizika, Vol. 48, No. 2, pp. 281–290 (May 2005).  相似文献   

Molecular Gas and Dust in the Massive Star Forming Region S 233 IR     

Rui-Qing Mao  Qin Zeng Purple Mountain Observatory  Chinese Academy of Sciences  Nanjing  National Astronomical Observatories  Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2004,4(5):440-454

The massive star forming region S 233 IR is observed in the molecular lines CO J = 2-1, 3-2, NH3 (1,1), (2,2) and the 870#m dust continuum. Four submillimeter continuum sources, labelled SMM 1-4, are revealed in the 870μm dust emission. The main core, SMM1, is found to be associated with a deeply embedded near infrared cluster in the northeast; while the weaker source SMM2 coincides with a more evolved cluster in the southwest. The best fit spectral energy distribution of SMM1 gives an emissivity of β = 1.6, and temperatures of 32 K and 92 K for the cold- and hot-dust components. An SMM1 core mass of 246 M⊙ and a total mass of 445 M⊙ are estimated from the 870μm dust continuum emission.SMM1 is found to have a temperature gradient decreasing from inside out, indicative of the presence of interior heating sources. The total outflow gas mass as traced by the CO J = 3-2 emission is estimated to be 35 M⊙. Low velocity outflows are also found in the NH3 (1,1) emission. The non-thermal dominant NH3 line width as well as the substantial core mass suggest that the SMM1 core is a “turbulent,massive dense core”, in the process of forming a group or a cluster of stars. The much higher star formation efficiency found in the southwest cluster supports the suggestion that this cluster is more evolved than the northeast one. Large near infrared photometric variations found in the source PCS-IR93, a previously found highly polarized nebulosity, indicate an underlying star showing the FU Orionis type of behavior.  相似文献   

On the deep minimum state in the Seyfert galaxy MCG−6-30-15     

Christopher S. Reynolds  Jörn Wilms  Mitchell C. Begelman  Rüdiger Staubert  Eckhard Kendziorra 《Monthly notices of the Royal Astronomical Society》2004,349(4):1153-1166

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A Statistical Model for Predicting the Average Abundance Patterns of Heavier Elements in Metal-Poor Stars     

Bo Zhang  Yan-Xia Zhang  Ji Li  Qiu-He Peng Department of Physics  Hebei Normal University  Shijiazhuang Center of Theoretical Nuclear Physics  National Laboratory of Heavy Ion Accelerator  Lanzhou National Astronomical Observatories  Chinese Academy of Sciences  Beijing Department of Astronomy  Nanjing University  Nanjing 《中国天文和天体物理学报》2002,2(5):429-440

We have collected nearly all the available observed data of the elements from Ba to Dy in halo and disk stars in the metallicity range -4.0 <[Fe/H]< 0.5. Based on the observed data of Ba and Eu, we evaluated the least-squares regressions of [Ba/Fe] on [Fe/H], and [Eu/H] on [Ba/H]. Assuming that the heavy elements (heavier than Ba) are produced by a combination of the main components of s- and r-processes in metal-poor stars, and choosing Ba and Eu as respective representative elements of the main s- and the main r-processes, a statistical model for predicting the Galactic chemical evolution of the heavy elements is presented. With this model, we calculate the mean abundance trends of the heavy elements La, Ce, Pr, Nd, Sm, and Dy with the metallicity. We compare our results with the observed data at various metallicities, showing that the predicted trends are in good agreement with the observed trends, at least for the metallicity range [Fe/H]> -2.5. Finally, we discuss our results and deduce some importa  相似文献   

相关处理机多制式兼容性测试的初步结果     

舒逢春  张秀忠  郑为民 《中国科学院上海天文台年刊》2002,(1)

我国VLBI网包括上海佘山、乌鲁木齐和昆明 3个观测站 ,以及上海天文台研制的两台站相关处理机。上海佘山和乌鲁木齐站已升级成MK4制式和只使用薄磁带 ,而昆明站只能使用S2制式。因此 ,实现相关处理机对不同制式数据和薄磁带的兼容 ,是我国VLBI网顺利运行的关键。给出了多制式VLBI观测实验和相关处理的初步结果 ,总结了相关处理机升级后的处理能力 ,并对相关处理机的下一步发展作简单讨论  相似文献   

上海天文台2004年度的科研工作     

廖新浩 《中国科学院上海天文台年刊》2005,(1):1-6

简要回顾了中国科学院上海天文台2004年科研及相关工作情况。  相似文献