由对FRⅡ射电星系的X射线观测试预言射电噪活动星系核的X射线喷流     

白金明 《天文研究与技术》2003,(1):19-25

在早期的文章中,基于耀变体(Blazar)的知识,我们预言了在射电噪活动星系核(AGN)中心10 kpc范围内X射线喷流的存在.钱得拉(Chandra)卫星最近对低功率射电星系的X射线观测与我们的预言相一致.在本文中我们研究了kpc尺度喷流中的电子加速,并建议通过对强的FR Ⅱ射电星系中所预言的X射线喷流的钱得拉卫星的X射线的观测,来研究红的耀变体中的康普顿冷却以及在内部致密喷流和大尺度延伸喷流间环境的不同.以上的研究可以进一步检验我们的关于射电噪活动星系核中kpc尺度X射线喷流的模型.  相似文献   

新近对耀变体(Blazar)的X射线观测     

张有宏 《天文研究与技术》2003,(1):26-30

本文综述了ASCA ,RXTE ,BeppoSAX和XMM -NEWTON对TeV耀变体 (Blazar)X射线研究的最新进展。主要集中在X射线资料的时间和光谱分析的最重要的方面 ,包括功率谱密度 ,结构函数 ,带间时间延迟 ,同步峰值能量的漂移和谱演化。对这些新结果的物理意义也进行了简要讨论。  相似文献   

Probing the nuclear activity with supermassive black holes     

V.D. Ivanov  A. Alonso-Herrero 《Astrophysics and Space Science》2003,284(2):565-568

We report three new or updated techniques for probing the parameters of active galaxies based on the masses of their central black holes M_BH). First, we derived a near-IR analog of the bulge luminosity versus M_BH relationship. The low scatter makes it a promising new tool to study the black hole demographics. Next, we present relations between M_BH and the10 μm and 2-10 keV nuclear luminosity. They may help to study the M_BH evolution over wide redshift ranges. Finally, we measured M_BH in quasars from z ∼ 3.4 to z ∼ 0.3 to search directly for M_BH growth. Surprisingly, we found no evidence for growth implying that the majority of quasar host galaxies have undergone their last major merger at z ≥ 3. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Detailed comparison of the structures and kinematics of simulated and observed barred galaxies     

J. K. O'Neill  John Dubinski 《Monthly notices of the Royal Astronomical Society》2003,346(1):251-264

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The discovery of two distant, massive clusters of galaxies in the ROSAT All-Sky Survey     

A. C. Edge  H. Ebeling  †  M. Bremer  H. Röttgering  M. P. van Haarlem  R. Rengelink  N. J. D. Courtney 《Monthly notices of the Royal Astronomical Society》2003,339(4):913-924

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Morphology and Luminosity Segregations in Galaxy Groups     

M. Girardi  F. Mardirossian  M. Mezzetti  E. Rigoni 《Astrophysics and Space Science》2003,285(1):31-35

We study morphology and luminosity segregation of galaxies in groups. We analyze the two catalogs of (∼2×400) groups which have been identified in the Nearby Optical Galaxy sample, by means of hierarchical and percolation `friends-of-friends' methods. We find that earlier-type (brighter) galaxies are more clustered and lie closer to the group centers, both in position and in velocity, than later-type (fainter) galaxies. Spatial segregations are stronger than kinematical segregations. These effects are generally detected at the ≳3-sigma level, with the exception of morphological segregation in velocity, which is the weakest effect. Our main results are confirmed by the analysis of statistically more reliable groups (with at least five members), and are strengthened by the detection of segregation in both hierarchical and percolation catalogs. Luminosity segregation is shown to be independent of morphology segregation. Our conclusions agree with a continuum of segregation properties of galaxies in systems, from low-mass groups to massive clusters. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Large-scale structure in the NIR-selected MUNICS survey     

C.S. Botzler  J. Snigula  R. Bender  N. Drory  G. Feulner  G.J. Hill  U. Hopp  C. Maraston  C. Mendes de Oliveira 《Astrophysics and Space Science》2003,284(2):393-396

The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep, photometric survey selected in the K' band. The project's main scientific aims are the identification of galaxy clusters up to redshifts of unity and the selection of a large sample of field early-type galaxies up to z < 1.5 for evolutionary studies. We created a Large Scale Structure catalog, using a new structure finding technique specialized for photometric datasets, that we developed on the basis of a friends-of-friends algorithm. We tested the plausibility of the resulting galaxy group and cluster catalog with the help of Color-Magnitude Diagrams (CMD), as well as a likelihood- and Voronoi-approach. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Measuring shapes of galaxy images – I. Ellipticity and orientation     

Nurur Rahman  Sergei F. Shandarin 《Monthly notices of the Royal Astronomical Society》2003,343(3):933-948

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Search for groups of extragalactic radio sources     

A. G. Gubanov  A. I. Kopylov  A. S. Potapov 《Astronomy Letters》2003,29(4):224-235

We explore the possibility of searching for groups of radio sources from the FIRST catalog on angular scales 1′–5′. We developed an efficient method of searching for such groups that takes into account the need for combining the components of extended sources represented in the catalog by separate objects. We found 31 groups of radio sources with angular sizes <5′ that contain no fewer than five sources with flux densities ≥3 mJy. This number is at least triple the expected number of such groups for a random Poisson distribution of radio sources in the sky. The prospects for using groups of radio sources to detect and study distant systems of galaxies are discussed.  相似文献   

Bar dissolution in non-spherical halos     

Makoto Ideta 《Astrophysics and Space Science》2003,284(2):531-534

Dynamical evolution of N-body bars embedded in spherical and prolate dark matter halos is investigated. In particular, the configuration such that galactic disks are placed in the plane perpendicular to the equatorial plane of the prolate halos is considered. Such a configuration is frequently found in cosmological simulations. N-body disks embedded in a fixed external halo potential were simulated, so that the barred structure was formed via dynamical instability in initially cool disks. In the subsequent evolution, bars in prolate halos dissolved gradually with time, while the bar pattern in spherical halos remained almost unchanged until the end of simulations. The e-folding time of bars suggest that they could be destroyed in a time smaller than a Hubble time. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献