The Structure of the Galactic Halo

We used the star counts in 21 BATC fields obtained with the National Astronomical Observatories (NAOC) 60/90 cm Schmidt Telescope to study the structure of the Galactic halo.Adopting a de Vaucouleurs γ/4 law halo,we found that the halo is somewhat flatter (c/a～0.4) towards the Galactic center than in the anticentre and antirotation direction (c/a ＞ 0.4).We also notice that the axial ratios are smaller (flatter) towards the low latitude fields than the high latitude fields,except for a few fields.We provide robust limits on the large-scale flattening of the halo.Our analysis shows that the axial ratio of the halo may vary with distance and the observation direction.At large Galactocentric radii,the halo may not have a smooth density distribution,but rather,it may be largely composed of overlapping streams or substructures,which provides a support for the hybrid formation model.     

Classification of extremely red objects in the Hubble Ultra Deep Field

We present a quantitative study of the classification of Extremely Red Objects (EROs). The analysis is based on the multi-band spatial-and ground-based observa-tions (HST/ACS-BViz, HST/NICMOS-JH, VLT-JHK) in the Hubble Ultra Deep Field (UDF). Over a total sky area of 5.50 arcmin2 in the UDF, we select 24 EROs with the color criterion (i-K)vega 3.9, corresponding to (I-K)vega 4.0, down to KVega = 22. We develop four methods to classify EROs into Old passively evolving Galaxies (OGs) and Dusty star-forming Galaxies (DGs), including (i-K) vs. (J-K) color diagram,spectral energy distribution fitting method, Spitzer MIPS 24μm image matching, and nonparametric measure of galaxy morphology, and found that the classification results from these methods agree well. Using these four classification methods, we classify our EROs sample into 60Gs and 8 DGs to KVega < 20.5, and 80Gs and 16 DGs to KVega < 22, respectively. The fraction of DGs increases from 8/14 at KVega < 20.5to 16/24 at Kvega < 22. To study the morphology of galaxies with its wavelength, we measure the central concentration and the Gini coefficient for the 24 EROs in our sample in HST/ACS-i, z and HST/NICMOS-J, H bands. We find that the morphological param-eters of galaxies in our sample depend on the wavelength of observation, which suggests that caution is necessary when comparing single wavelength band images of galaxies at a variety of redshifts.     

用WWZ变换分析类星体3C 345的光变周期

介绍了一种全新的基于小波分析原理的处理非等间隔数据的方法:加权小波Z变换(Weighted Wavelet Z-transform,WWZ).收集了类星体3C 345光学B波段100多年来较为完整的观测数据,获得了其长期光变曲线.利用WWZ变换对3C 345 B波段28 yr的光变数据进行分析,通过研究发现3C 345的光变曲线中包含有624～941 d、4.54～5.23 yr和9.59～11.51 yr的周期成分,并分析了它们随时间演化的情况.其中后两个周期成分属于稳定周期,而前一个周期成分波动比较大,可以推测它并不是一个稳定周期.     

贫金属星重元素丰度分布的参数化研究

基于大量贫金属星元素丰度的观测资料,以太阳系重元素丰度分布为标准,选取Sr、Ba、Eu分别作为贫金属星弱s-过程、主要s-过程、r-过程3种核合成的典型元素,采用参数化方法,分析了不同核合成过程对贫金属星重元素丰度的贡献比例.研究表明:金属丰度越高,弱s-过程、主要s-过程对较轻的中子俘获元素丰度的贡献就越大,较重的中子俘获元素主要由r-过程和主要s-过程产生;金属丰度较低,重中子俘获元素丰度主要由r-过程产生,星系早期弱s-过程对元素丰度几乎没有贡献.     

X—荧光交互有效—基本参数法及其在铝土矿和粘土分析中的应用

用熔融法制样，在基本参数法的基础上，结合交互有效法和ＰＲＥＳＳ值的计算，建立起稳定性较好的基体校正模型。分析结果表明，该法用较少标样即可满足定量分析铝土矿和粘土中十一个元素的要求，本软件可在ＵＮＩＸ、ＤＯＳ和ＸＥＮＩＸ操作系统下运行。     

2005年8月26日新疆墨玉5.4级地震序列

2005年8月26日新疆墨玉县发生了MS5.4地震,震区附近强烈有感,并造成了一定程度的破坏。本文从地震基本参数、震群监测、震源机制解、发震构造、地震序列等方面概述了这次地震序列。     

Origin and Properties of Strong MgⅡ Quasar Absorption Line Systems

Strong MgⅡ quasar absorption line systems provide us with a useful tool to understand the gas that plays an important role in galaxy formation. In this paper, placing the theories of galaxy formation in a cosmological context, we present semi-analytic models and Monte-Carlo simulations for strong MgⅡ absorbers produced in gaseous galactic haloes and/or galaxy discs. We investigate the redshift path density for the MgⅡ absorption lines and the properties of galaxy/absorber pairs, in particular the anti-correlation between the equivalent width of MgⅡ absorption line and the projected galaxy-to-sightline distance. The simulated result of the mean redshift path density of strong MgⅡ systems is consistent with the observational result. The fraction of strong MgⅡ systems arising from galaxy disks is predicted to be-10^ of the total. There exists an anti-correlation between the absorption line equivalent and the projected distance of sightline to galaxy center and galaxy luminosity.We determined that the mean absorbing radius Rabs≈29h^-1 kpc(LB/LB*)^0.35. After taking selection effects into consideration, this becomes Rabs≈38h^-1 kpc(LB/LB*)^0.18,which is in good agreement with the observational result. This shows the importance of considering selection effects when comparing models with observations.     

面向类旋涡星系盘有效厚度的获取及图像处理方法

面向类(face-on)旋涡星系盘的有效厚度或标高不能通过表面亮度测光的方式测量.为了获得面向类旋涡星系盘的厚度参数,将基于三维星系盘引力势Poisson方程在等角对数螺旋型物质密度扰动情形下的解,运用一种解析法对面向类旋涡星系盘的标高进行测算.为了去除星系核球的光污染而获得旋臂最内点位置(r0)的重要参数,使用了在星系观测图像中扣除双成份(盘+核球)测光模型的图像处理方法.通过对旋涡星系相关结构参数的拟合测量,各得到了一个普通旋涡星系(S)与棒旋星系(SB)的有效厚度与相关参数,并给出了它们的球盘比(rb/rd)和星系盘的标长与厚度之比(rd/H).采用这种在观测图像中扣除双成份测光模型的方法,将更容易看清旋臂结构的最内端,因而这里获得的禁区半径r0的数值往往比从原星系图像上直接测量的数值要小,获得的星系盘有效厚度将更薄.     

用相对定位法精细测定张北地震序列的时空参数

使用笔者改进了的相对地震定位方法对１９９８年１月１０日至５月３１日的张北地震序列中ＭＬ３．０级以上地震进行了重新测定,由于相对定位法能在一定程度上抵消地壳速度结构的横向不均匀性地震定位的影响,从而取得了较常规定位方法更精细的结果。     

849年振武、天德地震史料考证与地震基本参数再校订

对公元849年振武、天德地震史料进行了考证,认为:①地名“河西”是指唐代河西县,在今陕西合阳县黄河沿岸地区。②“云迦”是指唐代“云迦关”,可能在今包头西北石门附近。③这次地震“压死者数千人”。利用考证后的史料,对这次地震基本参数进行了再校订,确定这次地震为公元849年10月24日包头东河（40.6°N,110.1°E）7?级地震。