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151.
152.
S. G. Kleinmann M. G. Lysaght W. L. Pughe S. E. Schneider M. F. Skrutskie M. D. Weinberg S. D. Price K. Y. Matthews B. T. Soifer J. P. Huchra C. A. Beichman T. J. Chester T. Jarrett G. L. Kopan C. J. Lonsdale J. Elias J. W. Liebert P. Seitzer 《Experimental Astronomy》1994,3(1-4):65-72
This paper describes the design, expectations, and prototyping of a new allsky survey, called 2MASS (Two Micron All Sky Survey) to be carried out with the new generation of infrared array detectors. 相似文献
153.
本文研究了在1993年3月28日之前发现的899颗超新星(SNe)的样本.其中277颗SNe被用来研究超新星在其母星系中的径向分布.我们研究了四个星系样本中超新星在产生单个超新星(称为一般超新星)的星系及在产生多个超新星(称为多重超新星)的星系中的径向分布.这四个星系样本为:总旋涡星系样本,Sb~SbC星系样本,SC星系样本,Sc~Sd星系样本.研究的结果表明:一多重超新星比一般超新星在其母星系中具有更集中于星系核心(大多数恒星形成发生的地方)的倾向,说明星系中心的恒星形成活动会影响多重超新星事件的发生从而影响超新星的频率分布 相似文献
154.
本文在文[3]的基础上,考虑背景电磁波色散方程的弱磁化修正,在1<ωpe/Ωe<10的范围内(主委适用于太阳高日冕、行星际空间及星系射电喷流等),计算了由束流不稳定性直接放大正常模和反常模的增长率。增长率随着频率、ωpe/Ωe、电磁波传播角以及非热电子入射角等参数的变化规律,和忽略磁场时的结果与文[3]大体相同,但是反常模的增长,则随着ωpe/Ωe的增大而受到明显的抑制,因而在本文参数范围内,束流不稳定性所放大的电磁波以正常模为主,可以解释太阳III型爆发和星系射电喷流的偏振性质。 相似文献
155.
FITSIO软件包的简介及应用举例 总被引:1,自引:0,他引:1
简单介绍了用于读写FITS格式文件的FITSIO软件包的主要功能和特点。利用该软件包对 SDSS(Sloan Digital Sky Survey)数据中椭圆星系NGC4044和漩涡星系NGC5227的g,r,i三个波段的 FITS图像文件进行了重新读写,使这三个波段的FITS文件中天体的坐标完全对应。并以此合成了“真彩图”和“颜色分布图”,可以清楚地看出这些星系不同位置处颜色的变化。 相似文献
156.
Stellar photometry of images from the ACS and WFPC2 cameras on the Hubble Space Telescope (HST) is used to study the star composition and spatial distribution of stars in three edge-on visible spiral galaxies: NGC 891, NGC 4144, and NGC 4244. Measurements of the surface number density of old stars revealed two stellar subsystems in these galaxies: a thick disk and a halo. The boundaries of these subsystems, which consist mainly of red giants, are determined from the change in the gradient of the number density of the stars. The halos are flattened at the poles of the galaxies and extend to distances of 8–25 kpc from the planes of the galaxies. The present results on the number density distribution of stars with different ages perpendicular to the planes of these galaxies make it possible to improve our model for the stellar structure of spiral galaxies. The distances to these galaxies are calculated using a determination of the tip of the red giant branches (the TRGB method): D = 9.82 Mpc (NGC 891), D = 7.24 Mpc (NGC 4144), and D = 4.29 Mpc (NGC 4244).__________Translated from Astrofizika, Vol. 48, No. 2, pp. 261–280 (May 2005). 相似文献
157.
158.
基于2 km分辨率的ARW-WRF数值模拟资料,讨论了台风"珍珠"(2006)螺旋雨带中对流单体及内雨带的发展机制。结果表明:模式很好地再现了台风的路径和强度。作为雨带中仅仅存在于眼壁外侧的内雨带,其传播机制与重力波、涡旋Rossby波及混合波没有联系,其可能发展机制仅与低层出流、水平风场和变形场有关。低层出流使得内雨带径向向外运动,而低层的水平风场和变形场使其形成螺旋结构。同时,就螺旋雨带中精细对流单体的发展而言,涡度收支方程定量分析表明,其主要通过两种方式获得垂直涡度:水平涡度倾斜为垂直涡度;上升运动拉伸垂直涡度。随着平流输送,对流单体在眼壁附近合并和汇聚。 相似文献
159.
160.
Microstructural analysis of the classical spiral garnet porphyroblasts of south-east Vermont: evidence for non-rotation 总被引:2,自引:0,他引:2
N. HAYWARD 《Journal of Metamorphic Geology》1992,10(4):567-587
New data strongly suggest that the classical spiral garnet porphyroblasts of south-east Vermont, USA, generally did not rotate, relative to geographical coordinates, throughout several stages of non-coaxial ductile deformation. The continuity of inclusion trails (Si) in these porphyroblasts is commonly disrupted by planar to weakly arcuate discontinuities, consisting of truncations and differentiation zones where quartz–graphite Si bend sharply into more graphitic Si. Discontinuous, tight microfold hinges with relatively straight axial planes are also present. These microstructures form part of a complete morphological gradation between near-orthogonally arranged, discontinuous inclusion segments and smoothly curving, continuous Si spirals. Some 2700 pitch measurements of well-developed inclusion discontinuities and discontinuous microfold axial planes were taken from several hundred vertically orientated thin sections of various strike, from specimens collected at 28 different locations around the Chester and Athens domes. The results indicate that the discontinuities have predominantly subvertical and subhorizontal orientations, irrespective of variations in the external foliation attitude, macrostructural geometry and apparent porphyroblast-matrix rotation angles. Combined with evidence for textural zoning, this supports the recent hypothesis that porphyroblasts grow incrementally during successive cycles of subvertical and subhorizontal crenulation cleavage development. Less common inclined discontinuities are interpreted as resulting from deflection of anastomosing matrix foliations around obliquely orientated crystal faces prior to inclusion. Most of the idioblastic garnet porphyroblasts have a preferred crystallographic orientation. Dimensionally elongate idioblasts also have a preferred shape orientation, with long axes orientated normal to the mica folia, within which epitaxial nucleation occurred. Truncations and differentiation zones result from the formation of differentiated crenulation cleavage seams against porphyroblast margins, in association with progressive and selective strain-induced dissolution of matrix minerals and locally also the porphyroblast margin. Non-rotation of porphyroblasts, relative to geographical coordinates, suggests that deformation at the microscale is heterogeneous and discontinuous in the presence of undeformed, relatively large and rigid heterogeneities, which cause the progressive shearing (rotational) component of deformation to partition around them. The spiral garnet porphyroblasts therefore preserve the most complete record of the complex, polyphase tectonic and metamorphic history experienced in this area, most of which was destroyed in the matrix by progressive foliation rotation and reactivation, together with recrystallization. 相似文献