Stellar Populations in Bulges of Spiral Galaxies

We present a few results of a work in progress tackling the radial spectroscopic properties of bulges of spiral galaxies. This revised version was published online in September 2006 with corrections to the Cover Date.     

Classical Cepheids in the Galactic outer ring R1R ′2

The kinematics and distribution of classical Cepheids within ∼3 kpc from the Sun suggest the existence of the outer ring R₁R ′₂ in the Galaxy. The optimum value of the solar position angle with respect to the major axis of the bar, θ_b, providing the best agreement between the distribution of Cepheids and model particles, is θ_b = 37° ±13°. The kinematical features obtained for Cepheids with negative galactocentric radial velocity V_R are consistent with the solar location near the descending segment of the outer ring R₂. The sharp rise of extinction toward of the Galactic center can be explained by the presence of the outer ring R₁ near the Sun. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A study of the kinematics of unusually H I‐rich galaxies

We examine the H I kinematics of the “Bluedisk” ensemble of 48 galaxies selected from the Sloan Digital Sky Survey and observed in H I with the Westerbork Synthesis Radio Telescope. The sample consists of 25 galaxies with a high H I mass fraction and a comparatively large control sample comprising 23 galaxies of comparable stellar mass, stellar mass surface density, redshift, and inclination. By studying the H I velocity fields of these galaxies, we investigate whether there are signatures of ongoing gas accretion: i.e. global asymmetries and indications for warping and kinematical lopsidedness. We find no enhanced kinematical asymmetries between the H I‐rich sample and the control sample galaxies, indicating no significant difference in kinematical signatures such as warping and lopsidedness. Furthermore, we find no difference in position angle and systemic velocity offset with respect to the optical between both sub‐samples. We therefore do not find compelling evidence for enhanced global asymmetry of the H I‐excess galaxies ensemble properties in comparison to the control sample galaxies. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

台风螺旋雨带云结构和降水形成机制研究

应用数值模式结果,选择台风登陆后两个不同时次螺旋雨带中两个强降水中心,对台风螺旋雨带的云结构和降水形成机制进行诊断分析.结果发现螺旋雨带云结构和降水形成机制有如下特点:在9～13 km高空范围内冰晶的非均质核化非常活跃,冰晶转化率高于台风眼壁暴雨数倍,但是冰晶通过贝吉龙过程生长为雪、雪通过凝华增长生长为霰的过程相对台风眼壁很弱,螺旋雨带雨水形成微物理机制以霰粒子融化成雨水(pgmlt)为主,冰相粒子转化率大值区位于垂直上升气流大值区,8 km高度霰收集雪(dgacs)干增长是最主要的冰相粒子生长过程,与北方层状云比较,螺旋雨带暴雨冷云中的凝华过程和撞冻过程非常活跃.螺旋雨带云水凝结过程呈双峰型,位于7～8 km高度冷云区的云水凝结峰值较大,暖云区0.5～1.5 km高度云水凝结峰值次之.     

An Analysis of the Radio Light Variations of Blazars With Low Peak Frequencies

The data of light variations of six blazars with low peak frequencies (i.e., BL Lacerta, 0235+164, OQ530, 0716+714, 3C 345, and 3C 273) at 4.8, 8, 14.5, 22 and 37 GHz in the recent thirty years have been collected from immense amount of literature. By using the method of discrete correlation function the correlations and delays of the light curves of these six sources at the 5 wavebands are analyzed. With the method of structural function, the periods and timescales of the light variations of these six sources are analyzed, and their amplitudes of light variations are compared and analyzed. As revealed by the result of analysis, among the six blazars the amplitudes of light variations of 0716+714 and 0235+164 are relatively large, and those of 3C 345 and OQ 530 are less. The amplitudes of light variations of 3C 273 and BL Lacertae are relatively smaller. As shown by the multi-waveband analysis of delays between two neighboring wavebands, 0235+164 exhibits the tendency of variation that the high-frequency wavebands precede the low-frequency wavebands. On the whole, 3C 345 exhibits the tendency that the high-frequency wavebands lag be-hind the low-frequency wavebands. The analyses of the other blazars show that in a part of radio wavebands there appears the tendency of variation that the high-frequency waveband leads the low-frequency waveband. Yet in the other radio wavebands there appears the tendency that the high-frequency waveband lags behind the low-frequency waveband. As revealed by the results of analyses with the method of structural function, the timescale, fitted slope, and period of light variations of 3C 345 are larger than those of the other five blazars with low peak frequencies. This demonstrates that the activity of 3C 345 is comparatively weaker than the other five sources, and implies that in the interior of 3C 345 there may exist some physical processes which are different from those of the other five blazars with low peak frequencies.     

星爆后星系NGC4736核区的环状结构

在１９９２年３月３１日至４月２日期间，我们利用云南天文台１ｍ望远镜２号ＣＣＤ和缩焦装置，对环星系ＮＧＣ４７３６进行了Ⅴ和Ⅰ波段深曝光观测。在经过Ｒｉｃｈａｒｄｓｏｎ－Ｌｕｃｙ图象复原以及自适应滤波两种方法处理后，发现仅仅在Ⅴ波段图象上，其核区存在一个直径约为１０″的环状结构。     

星系的恒星速度弥散度的归算方法

星系的恒星视向速度分布是星系动力学模型的重要观测约束,其特征参数包括速度弥散度、分布轮廓以及红移。这些参数对研究星系的动力学、结构和演化以及中央黑洞的质量等都具有重要的价值。该文全面总结了从星系光谱归算星系的恒星视向速度分布及其弥散度的各种方法,以及对观测和处理的一些要求。这些方法都假设星系谱线可看作是模板星光谱经多普勒位移并加宽后的线性叠加。提取尽可能多的星系内部恒星运动信息、减少模板星失配的影响、简化误差分析,是这些方法追求的目标。