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从星系形成和演化的角度出发,对星系结构和动力学进行的粗略的评述,内容包括:(1)初步描述了星系中各主要成分的物理特征(空间分布,运行学和化学)及其形成和演化,(2)Damped Lyman-alpha systems(DLAs)是本地星系的化石,对其进行观测研究是HST的主要任务之一,对DLAs宽的谱线轮廓的物理机制和其恒星形成,化学演化进行了讨论,(3)目前已证明Lyman Break方法是发现高红移高恒星形成星系的有效手段,讨论了Lyman Break Galaxies的动力学过程和恒星形象,(4)旋涡星系和椭圆星系的Scaling Law是星系形成和演化所必须解释的问题,对近期该方面的研究结果作了介绍,(5)整体超星的反馈作用在星系形成和演化中起了重要作用,评述了该物理过程对星系演化的影响;(6)随着观测资料的不断积累,各种物体对河外背景辐射的贡献已成了一个重要的研究方向,讨论了宇宙整体的星形成历史和化学演化,(7)银河系是进行星系形成和演化研究的归算零点,介绍了银河系的结构,动力学及演化。 相似文献
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用一个星系相互作用数值模拟的综合三体模型,研究椭圆星系是否由盘星系合并而成,结果表明,主要取决于星系的盘面积和星系运行轨道面的夹角,如果夹角不等于零,盘星系的相互作用是可能形成椭圆星系的,否则还是盘星系。 相似文献
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本文对Virgo星系团中央6°天区内的成员星系作了光度函数和质量函数的研究。成员星系是以视向速度作为判据并合理地考虑了密度分布因素后确定的。研究表明,该天区全部成员星系的光度函数为Schechter型,而各类S星系的光度函数则为Gauss型,且峰值位置按Sa→Sd序列向暗端移动,宽度亦逐渐变宽;Virgo团质量函数与恒星质量函数一样可以用指数形式来描述,文中还利用光度函数和质量函数对该团的形态和质量分层进行了讨论,并计算了该天区团的总光度。 相似文献
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刘步林 《中国天文和天体物理学报》1994,(4)
用一个星系相互作用数值模拟的综合三体模型,研究椭圆星系是否由盘星系合并而成。结果表明,主要取决于星系的盘面和星系运行轨道面的夹角。如果夹角不等于零,盘星系的相互作用是可能形成椭圆星系的,否则还是盘星系。 相似文献
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介绍了我们对极亮红外星系研究的系列工作。这些工作包括对星系并合激发星暴和星系核活动并最终形成椭球星系的演化过程。特别介绍了星系多重并合的观测证据和IRQSO与窄线Seyfert 1(NLS1)、低电离宽吸收线类星体之间可能的演化关系 相似文献
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星暴星系是一类内部正在发生极为剧烈恒星形成的天体。介绍了星暴星系的研究历史及星暴星系的定义。综述了从射电波段到X射线波段星暴星系的光度光谱观察特征及其研究的最新进展。列出了星暴星系研究中存在的一些热点问题,包括星暴的触发机制,星暴时标,星族组分,恒星形成率,内红化以及星暴星系与活动星系核之间的关系等。最后,简述了可能有助于解决这些问题的观测手和理论方法。 相似文献
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盘星系的内禀扁度对计算星系的空间倾角非常重要.对从LEDA数据库中选取的14988个盘星系进行内禀扁度的统计分析.研究表明,盘星系的内禀扁度与星系的形态密切相关.整体上说,透镜星系和不规则星系的内禀扁度qo大于旋涡星系,早型旋涡星系的内禀扁度qo大于晚型旋涡星系,其中Scd星系的内禀扁度qo最小.利用所得的qo-T关系,还对16个已知倾角的亮星系进行了倾角计算,发现与其他方法估计的空间倾角符合得较好. 相似文献
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Yu. A. Rylov 《Astrophysics and Space Science》1985,117(1):5-34
The self-consistent balanced pulsar magnetosphere of a magnetic neutron star with aligned magnetic and rotational axes is considered. It is shown that the magnetosphere consists of electron polar caps separated by empty space from a positron equatorial belt. The shape of the cold polar caps at a large distance from the star is calculated. It is shown that the cap shape at a large distance is independent of the magnetospheric structure near the neutron star. The shape of the equatorial belt is calculated. It is shown that a part of the equatorial belt rotates differentially, and its angular velocity is larger than that of the star (superrotation). It is shown that under certain conditions the space charge density of the belt can be very large. In principle, the formation of a surface charge placed in vacuum on a magnetic surface is possible. Magnetospheric vibrations are considered. A connection is established between drifting subpulses and the equatorial belt superrotation and also between drifting subpulses and cap vibrations. The characteristic frequency of vibrations and the angular velocity of superrotation are estimated. 相似文献
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E. A. Belbruno 《Celestial Mechanics and Dynamical Astronomy》1981,25(4):397-415
A new regularizing transformation for the three-dimensional restricted three-body problem is constructed. It is explicitly derived and is equivalent to a simple rational map. Geometrically it is equivalent to a rotation of the 3-sphere. Unlike the KS map it is dimension preserving and is valid inn dimensions. This regularizing map is applied to the restricted problem in order to prove the existence of a family of periodic orbits which continue from a family of collision orbits. 相似文献
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Henning Knutsen 《Astrophysics and Space Science》1988,140(2):385-401
An exact solution of Einstein's field equations for an isentropic fluid sphere is examined. It turns out that the crucial factor for the physical properties and the stability of this model is the degree of incompressibility. Necessary and sufficient conditions are given for the weak and the strong energy conditions to be fulfilled and for the speed of sound to be less than the speed of light. The speed of sound always has a minimum at the center of the fluid sphere. But two possibilities exist: either the speed of sound is increasing all the way outwards to the surface of the sphere, or the speed of sound is first increasing, then reaching a maximum when still inside the fluid sphere, and thereafter decreasing outwards to the surface. The adiabatic index is investigated and is found to be increasing outwards for the actual degrees of compressibility. This adiabatic index is always greater than unity, and the temperature is thus decreasing throughout the sphere. The necessary and sufficient condition for the adiabatic index to be greater than 4/3 is also given. (This is a necessary condition for the fluid sphere to be stable.) Chandrasekhar's pulsation equation with boundary conditions is investigated, and the fluid sphere is found to bestable if and only if the degree of incompressibility is greater than a certain value.Dedicated to the memory of the late Bronislaw Kuchowicz. 相似文献
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对中国古代彗星记录的研究状况进行了全面论述,讨论了古代彗星名称、记录和轨道的确定,以事实说明,据这些彗星记录不可能得垤精确的轨道;回顾了古代彗星证认的历史发展,着重分析进行短周期彗得证认时可能出现的问题和解决方法;总结了古代彗星证认的意义:一是有助于短周期彗星长期演化的研究,二是有助于历史年代的确定。 相似文献
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Propagation of torsional waves along isothermal and initially-untwisted magnetic-flux tubes embedded in the solar atmosphere
is studied analytically. Conditions for wave propagation along thin and wide magnetic-flux tubes are determined, and it is
shown that the propagation along thin tubes is cutoff free; however, for wide tubes the propagation is affected by a cutoff
frequency. A method to determine the cutoff frequency is presented and applied to a specific model of solar magnetic flux
tubes. An interesting result is that the cutoff frequency is a local quantity in the model and that its value at a given height
determines the frequency that torsional tube waves must have to propagate at this height. 相似文献
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Ding-Qiang Su Xiang-Qun Cui National Astronomical Observatories/NIAOT Chinese Academy of Sciences Nanjing Department of Astronomy Nanjing University Nanjing 《中国天文和天体物理学报》2004,4(1):1-9
Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is one of the major national projects under construction in China. Active optics is one of the most important technologies for new large telescopes. It is used for correcting telescope errors generated by gravitational and thermal changes. Here, however, we use this technology to realize the configuration of LAMOST, -a task that cannot be done in the traditional way. A comprehensive and intensive research on the active optics used in LAMOST is also reported, including an open-loop control method and an auxiliary closed-loop control method. Another important development is in our pre-calibration method of open-loop control, which is with some new features: simultaneous calculation of the forces and displacements of force actuators and displacement actuators; the profile of mirror can be arbitrary; the mirror surface shape is not expressed by a fitting polynomial, but is derived from the mirror surface shape formula which is highly accurat 相似文献
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We present new differential, four-color photoelectric photometry for the eclipsing binary TV Cet. UBVR light curves and radial velocities published previously are solved simultaneously using the Wilson–Devinney computer program. Our solutions indicate that TV Cet includes a third light contribution with 2.3% in U, 1.9% in B, 1.3% in V and 1.6% in R. The masses of the component stars are and , while the radii are and for the primary and secondary components, respectively. Using new absolute properties and our previous results from period analysis, we calculated the observational and theoretical internal structure constants to be and , respectively. Taking into account the third light contribution from the Wilson–Devinney solution and properties of the third body orbit from period analysis, the mass of the third body is obtained as , corresponding to the inclination value . Evolutionary status of the component stars is also studied. We present the position of the stars in an H–R diagram for solar compositions. 相似文献
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Ballistic capture of spacecraft and celestial bodies by planets of the solar system is studied considering the elliptic restricted
three body model. A preferential region, due to the eccentricity of the planet and the Sun-gravity-gradient effect is found
for the capture phenomenon. An analytical formula is derived which determines the limiting value of the satellite capture
eccentricity ec as a function of the pericenter distance xp and planet’s true anomaly. The analytic values ec are tested by a numerical propagator, which makes use of planetary ephemeris, and only a small difference with respect to
numerical integration is found. It turns out that lower values of ec occur when the planet anomaly is close to zero; that is, capture is easier when the planet is at its perihelion. This fact
is confirmed by the capture of celestial bodies. It is shown that Jupiter comets are generally captured when Jupiter is in
its perihelion region. Ballistic capture is also important in interplanetary missions. The propellant saved using the minimum
ballistic capture eccentricity is evaluated for different missions and compared with respect to the case in which the insertion
orbit is a parabola: a significant saving can be accomplished. 相似文献