Neutron Star Motion in the Disk Galaxy

The neutron star motions are based on the undisturbed finitely thick galactic disk gravitational potential model. Two initial conditions, i.e. the locations and velocities, are considered. The Monte Carlo method is employed to separate rich diversities of the orbits of neutron stars into several sorts. The Poineare section has the potential to play an important role in the diagnosis of the neutron star motion. It has been observed that the increasing ratio of the motion range vertical to the galactic plane to that parallel to the galactic plane results in the irregularity of neutron star motion.     

Long-Time Behavior for the Two-Dimensional Motion of a Disk in a Viscous Fluid

In this article, we study the long-time behavior of solutions of the two-dimensional fluid-rigid disk problem. The motion of the fluid is modeled by the two-dimensional Navier–Stokes equations, and the disk moves under the influence of the forces exerted by the viscous fluid. We first derive L ^p ?L ^q decay estimates for the linearized equations and compute the first term in the asymptotic expansion of the solutions of the linearized equations. We then apply these computations to derive time-decay estimates for the solutions to the full Navier–Stokes fluid-rigid disk system.     

Dark-matter annihilation in the Galaxy

The possibility of amplification of the annihilation signal from dark matter in the Galaxy halo due to its clusterization into small-mass clumps (about the Moon’s or Earth’s mass) is discussed. Formation of dark-matter clumps is considered within the conventional cosmological model taking into account their hierarchical clustering and tidal destruction. It is shown that the amplification factor of γ rays from dark-matter annihilation due to small-mass clumps in the Galaxy may range from 10 to 1000.     

Cosmic-ray propagation in the Galaxy

Summary More than 95 contributed papers on cosmic-ray transport and acceleration in the Galaxy were presented at the XXIV International Cosmic-Ray Conference. The present summary covers part of the rapporteur talk and reflects a personal view of the subject. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Dark matter annihilation in the Galaxy

The awaited dark matter (DM) neutralino annihilation signal from the galactic halo crucially depends on the presence of small-scale clumps. A mass function of the DM small-scale clumps is calculated in the standard cosmological scenario. The final distribution of clumps in the Galaxy is influenced by their tidal destruction. The basic sources of clump destruction are (i) clumps of larger scales, (ii) the gravitational field of the galactic disk, (iii) the stars in the galactic bulge, and (iv) the stars in the galactic halo. The destruction of clumps due to their mutual tidal interactions is important at earl stages of hierarchical clustering and the galactic halo formation. The clumps surviving through the hierarchical clustering are continuously destroyed by interactions with the galactic disk and stars. It is shown that, among the Moon or Earth mass DM clumps surviving through the hierarchical clustering, only 20% will further survive near the Sun’s position mainly because of the tidal destruction by the galactic disk. This reduction of DM clump density significantly diminishes the expected DM annihilation signal from the galactic halo. The text was submitted by the authors in English.     

Destruction of axion miniclusters in the Galaxy

Previously, it has been established that axion dark matter (DM) is clustered to form clumps (axion miniclusters) with masses M ≈ 10^–12 M _⊙. The passages of such clumps through the Earth are very rare events occurring once in 10⁵ years. It has also been shown that the Earth’s passage through DM streams, which are the remnants of clumps destroyed by tidal gravitational forces from Galactic stars, is a much more probable event occurring once in several years. In this paper, we have performed detailed calculations of the destruction of miniclusters by taking into account their distribution in orbits in the Galactic halo. We have investigated two DM halo models, the Navarro–Frenk–White and isothermal density profiles. Apart from the Galactic disk stars, we have also taken into account the halo and bulge stars. We show that about 2–5% of the axion miniclusters are destroyed when passing near stars and transform into axion streams, while the clump destruction efficiency depends on the DM halo model. The expected detection rate of streams with an overdensity exceeding an order of magnitude is 1–2 in 20 years. The possibility of detecting streams by their tidal gravitational effect on gravitational-wave interferometers is also considered.     

Neutrino Burst Monitoring in Our Galaxy

Journal of Experimental and Theoretical Physics - Baksan underground scintillation telescope (BUST) operates under the program of neutrino burst search since the middle of 1980. We report the...     

About Cosmic Ray Sources in Galaxy

Physics of Atomic Nuclei - In the last two decades the new experimental data on cosmic rays concerning energy spectra in a wide energy range up to 10 $${}^{14}$$ eV, isotropy, ratio of positron...     

Fractional models of cosmic ray acceleration in the Galaxy

Possible formulations of the problem of the acceleration of cosmic rays in the interstellar galactic medium with fractional differential equations have been considered. The applied technique has been physically justified. A Fermi result has been generalized to the case of the acceleration of particles in shock waves in the supernovae remnants fractally distributed in the Galaxy.     

关于"太阳在银河系中所受引力与到银心距离r的关系"的讨论

讨论了银道面内的引力场强分布和太阳在银河系中所受引力与到银心距离r的关系，指出引力场强g并不是与r的平方成反比，这是由于银河系的大小和形状不能忽略造成的．强调了万有引力定律的适用条件．     

Galactic emissions: seeing through the Galaxy

The diffuse matter in our Galaxy is certainly to be damned by the cosmologist because it pollutes the CMB sky with the various emissions from its components: dust, ionised gas (free–free) and energetic particles (synchrotron). We detail here our knowledge, but also the unknowns, regarding these radiation sources. As we are not in a position to be able to physically escape our Galaxy, the better knowledge of these foreground components is our only hope to build a consistent model which will at least allow us a virtual escape. However, the detailed understanding of the physics of the different emissions and of the large scale distribution of the various emitters is a delight for many of us. We will show here some aspects, with a peculiar emphasis on a possible emission from tiny rotating grains. To cite this article: M. Giard, G. Lagache, C. R. Physique 4 (2003).     

Galaxy formation just after the recombination period

A scenario of galaxy formation is outlined which is based essentially on the fact that the cosmic matter about 10⁶yr after the end of the recombination period is a general relativistic Boltzmann gas very close to equilibrium. In this scenario the observed very small inhomogeneities of the background radiation lead to very sharply edged gas clouds in the centres of the inhomogeneities. The universe between the clouds is completely swept clean of matter. If one assumes the centres of the inhomogeneities to be axially symmetric, the mass spectrum of the clouds extends from the smallest globular clusters withM 10⁵ M as the lower limit (spherical symmetry) up to the big spiral galaxies withM 10¹¹ M as the upper limit (maximal flattening). The upper limit masses are extremely thin pancakes which contract within a time interval of about 2 · 10⁹ years to the proportions of an ordinary spiral galaxy of today.     

The spatial distribution of old neutron stars in the Galaxy

The spatial distributions of old neutron stars (NSs) with ages 109 to 1010 yr in our Galaxy are investigated by Monte Carlo simulation under two different initial random velocity models.It is found that the scale heights of the distribution increase with the Galactic radial distance.The location of the peak of the NS distribution is closer to the Galactic center than that of their progenitors.The results from our detailed numerical analysis reveal that there is resemblance between the simulated old NS distribution and the structure of the observed HI disk.     

Grand-scale low-mass star formation in our Galaxy

Summary We present the first results of an observational programme to identify star forming regions and to provide the near-infrared energy distributions of embedded objects selected by their IRAS colours. Based on data collected at the European Southern Observatory, La Silla, Chile.     

Unstable and Stable Galaxy Models

To determine the stability and instability of a given steady galaxy configuration is one of the fundamental problems in the Vlasov theory for galaxy dynamics. In this article, we study the stability of isotropic spherical symmetric galaxy models f ₀(E), for which the distribution function f ₀ depends on the particle energy E only. In the first part of the article, we derive the first sufficient criterion for linear instability of f ₀(E) : f ₀(E) is linearly unstable if the second-order operator

星敏感器恒星检测若干问题研究

介绍了星敏感器的基本组成及工作过程。对恒星检测所涉及的一些问题,如视场内可探测恒星平均数、星图处理、恒星像点位置确定等问题进行了研究和实际验证。     

Simultaneity on the Rotating Disk

The disk that rotates in an inertial frame in special relativity has long been analysed by assuming a Lorentz contraction of its peripheral elements in that frame, which has produced widely varying views in the literature. We show that this assumption is unnecessary for a disk that corresponds to the simplest form of rotation in special relativity. After constructing such a disk and showing that observers at rest on it do not constitute a true rotating frame, we choose a “master” observer and calculate a set of disk coordinates and spacetime metric pertinent to that observer. We use this formalism to resolve the “circular twin paradox”, then calculate the speed of light sent around the periphery as measured by the master observer, to show that this speed is a function of sent-direction and disk angle traversed. This result is consistent with the Sagnac Effect, but constitutes a finer analysis of that effect, which is normally expressed using an average speed for a full trip of the periphery. We also use the formalism to give a resolution of “Selleri’s paradox”.     

非旋转银河系的重力不稳定性

银河系中星体分布的重力不稳定性在天文物理是个熟知的问题.尝试以加速器物理的方法初步分析了这个现象, 得到非旋转银河系在它的大小超过某阈值时会呈现不稳定现象的结论,而此阈值与银河系的质量密度有关.     

On the Distribution of Radio Pulsars Above the Galaxy Plane

A mechanism of pulsar accumulation over the galaxy plane, caused by deceleration in the gravitational field and stopping at a certain distance of z from the plane is proposed. For pulsars with velocities close to the average observed velocity of about 300 km/s, the consideration of kinematics of such motion estimates the age of stopped pulsars of the order of ten millions years and the average distance from the galaxy plane of about 2 kpc. The consistency in the pulsar longitude distribution at |z| = 0.45–4.5 kpc and the distribution of the formation regions of massive stars in the galaxy disk was found.     

星模拟器星点能量中心修正方法的研究

对星模光学系统中各种像差对几何中心位置的影响及像差对显示星点能量中心位置造成的偏差进行了分析与综合评估.分析结果表明,视场位置越大的星点产生的像点能量越不均匀,重心偏移越明显,系统中慧差和畸变对于星点能量中心影响较大.根据球面镜组成的共轴光学系统性质可知,能量中心的偏移发生在星点所在极半径方向上,因此提出了一种基于极坐标的星点位置修正方法,只需在星点所在方向对极半径进行修正.该方法简化了基于二维坐标轴分区修正的过程,减少了数据计算量.利用极坐标修正方法对星模拟器修正前后的单星位置误差进行了测试,实验结果表明极坐标修正过程较以往修正方法简单快捷,且修正结果更加准确.