射电类星体的演化与宇宙学红移

收集了142个射电类星体(28个射电宁静类星体、114个射电噪类星体)、43个核占优型射电类星体、82个瓣占优型射电类星体和80个Seyfert星系的样本,基于Logistic非线性回归分析的方法对红移和热光度、黑洞质量、5 GHz射电光度、爱丁顿吸积率、核主导参数R的关系进行研究,拟合出相应的演化曲线,得到如下结论:(1)射电类星体的演化是从射电噪类星体(RLQ)演化到射电宁静类星体(RQQ),当演化到一定阶段射电类星体过渡到Seyfert星系;(2)核占优型射电类星体(CDQ)和瓣占优型射电类星体(LDQ)之间并没有明显的随红移演化.     

8个ROSAT X射线源和5G射电源被证认为类星体

１９９５年５月，使用２．１６ｍ望远镜对ＲＯＳＡＴＸ射线源进行光学证认期间，发现８个ＲＯＳＡＴＸ射线源和５Ｇ射电源的光学对应体是以前未发现的类星体，其红移范围从０．３３３至１．０９１。本文给出了这些类星体的多波段特性。     

Application of principal component analysis to radio properties of Quasars

The principal component analysis method has been applied to two samples of nearby and distant quasars with well known radio data. Relationships between physical parameters pertinent to radio morphology has been searched and the significant number of dimensions of the manifold has been found to be two. The results of this analysis confirm the existence of a redshift luminosity correlation for a subset of 36 nearby, but to a lesser extent for 43 distant, quasars. An anticorrelation seems to exist between luminosity and linear sizes for the last sample. On the other hand, application of this analysis to the above samples indicates no correlation between the viewing angle and the other physical parameters.     

Measuring the Probabilistic Photometric Redshifts of X-ray Quasars Based on the Quantile Regression of Ensembles of Decision Trees

We present empirical machine learning algorithms for measuring the probabilistic photometric redshifts (photo-z) of X-ray quasars based on the quantile regression of ensembles of decision trees. Relying on the data of present-day photometric sky surveys (e.g., SDSS, GALEX, WISE, UKIDSS, 2MASS, FIRST), the proposed methods allow one to make high-quality photo-z point predictions for extragalactic objects, to estimate the confidence intervals, and to reconstruct the full probability distribution functions for all predictions. The quality of photo-z predictions has been tested on samples of X-ray quasars from the 1RASS and 3XMM DR7 surveys, which have spectroscopic redshift measurements in the SDSS DR14Q catalog. The proposed approaches have shown the following accuracy (the metrics are the normalized median absolute deviation σNMAD and the percentage of outliers n_>0.15): σ_NMAD, n_>0.15 = 0.043, 12% (SDSS + WISE), 0.037, 8% (SDSS + WISE + GALEX) and 0.032, 8.6% (SDSS + WISE + GALEX + UKIDSS) on the RASS sample; σ_NMAD, n_>0.15 = 0.054, 13% (SDSS + WISE), 0.045, 7.6% (SDSS + WISE + GALEX), and 0.037, 6.6% (SDSS + WISE + GALEX + UKIDSS) on the 3XMM sample. The presented photo-z algorithms will become an important tool for analyzing the multi-wavelength data on X-ray quasars in the forthcoming Spectrum–Roentgen–Gamma sky survey.     

Optical Spectroscopy of Quasars Discovered by SRG/eROSITA with a 2.5-m Telescope at the Caucasus Mountain Observatory of SAI MSU

Astronomy Letters - Based on observations with the transient double-beam spectrograph (TDS) at the 2.5-m telescope of the Caucasus Mountain Observatory of SAI MSU, we have determined the redshifts...     

Dynamics of a Cosmological Model with a Conformally-Coupled Scalar Field

Astrophysics - Cosmological evolution is examined in a model with a conformally-coupled scalar field and with a cosmological constant. Models of this type arise in two types of gravitational...     

Cosmological dynamics of a quintom field on the warped DGP brane

As a generalization of the Brans-Dicke type scalar-tensor gravity in a braneworld context, we study cosmological phase space of a braneworld model with induced gravity in the presence of a scalar field on the brane. We consider a quintom field minimally or non-minimally coupled to induced gravity on the warped DGP brane and we present a detailed analysis of the critical points, their stability and late-time cosmological viability of the solutions within a phase space approach. In particular, de Sitter solutions, different from the famous self-accelerated branch of the DGP model are found and the phase-space analysis for checking their attractor properties is performed. We analyze also the possibility of crossing of the phantom divide by the effective equation of state parameter of the model. We also focus on the classical stability of the solutions in w–w′ phase plane.     

Cosmological dynamics of a bulk scalar field in the DGP setup

We reconsider the issue of cosmological dynamics in a DGP setup with a bulk scalar field. The ghost-free, normal branch of this DGP-inspired braneworld scenario has the potential to realize a self-consistent phantom-like behavior. The roles played by the bulk canonical scalar field on this phantom-like dynamics are explored. Within a dynamical system approach, the effective phantom nature of the scenario is investigated with details. This analysis shows that there is a stable, late-time de Sitter phase.     

非零宇宙常数Global Monopole的引力场

本文讨论了膨涨宇宙处于宇宙常数不为零时ＧｌｏｂａｌＭｏｎｏｐｏｌｅ存在的可能性、稳定性及求其引力场的解。最后分析了ＧｌｏｂａｌＭｏｎｏｐｏｌｅ的宇宙演化。     

Prospects of the Multi-channel Photometric Survey Telescope in the Cosmological Application of Type Ia Supernovae

The Multi-channel Photometric Survey Telescope(Mephisto) is a real-time, three-color photometric system designed to capture the color evolution of stars and transients accurately. This telescope system can be crucial in cosmological distance measurements of low-redshift(low-z, z ■ 0.1) Type Ia supernovae(SNe Ia). To optimize the capabilities of this instrument, we perform a comprehensive simulation study before its official operation is scheduled to start. By considering the impact of atmospheri...     

低纬子午环光轴变化的内涵和测定方法

叙述了子午环观测中测定和修正光轴变化或镜筒弯曲的必要性，简述了传统子午环的测定和修正方法，论述了低纬子午环引起光轴变化的因素和实时测定光轴变化的方法，讨论了在光轴变化测定值中的误差来源。     

Cosmological dynamics of EDGP model with a tachyon field on the brane

We consider the cosmological dynamics of a tachyon field localized on the extended DGP braneworld scenario. We present a detailed analysis of the critical points in the phase space of the model, their stability and late-time cosmological viability of the solutions. We study the luminosity distance behavior of this ?EDGP model and compare it with ΛCDM model. Also we show that the EDGP solutions in the presence of tachyon field can explain late time acceleration of the universe.     

On Some Bianchi Type Cosmological Models in a Bimetric Theory of Gravitation

Spatially-homogeneous and anisotropic Bianchi type-III, V, VI₀ cosmological models in Rosen's (1973) bimetric theory of gravitation are considered. It is shown that, in each case, when the soure of the gravitation field is a perfect fluid distribution Bianchi type cosmological models do not exist. Hence vacuum models are presented and studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cosmological dynamics of a non-minimally coupled bulk scalar field in DGP setup

We consider cosmological dynamics of a canonical bulk scalar field, which is coupled non-minimally to 5-dimensional Ricci scalar in a DGP setup. We show that presence of this non-minimally coupled bulk scalar field affects the jump conditions of the original DGP model significantly. Within a superpotential approach, we perform some numerical analysis of the model parameter space and consider bulk-brane energy exchange in this setup. Also we show that the normal, ghost-free branch of the DGP solutions in this case has the potential to realize a self-consistent phantom-like behavior and therefore explains late time acceleration of the universe in a consistent way.     

定天镜的伺服驱动原理

主要介绍恒星光干涉仪实验系统的定天镜伺服驱动原理．采用电细分和逐级升、降速的方法来减小定天镜在转动时的振动，提高定位、跟踪精度．由于应用了４００的电细分和１０００倍的传速比，步进电机的步距角达到０．００６４８°．     

Toward a model of a two-component solar cycle

In a two-component cycle, the generation of the dipole field by a separate mechanism as well as the strong link occurring, with a 5–6-yr delay, between the sunspot cycle and the preceding dipole cycle, sets in new terms the problem of the mechanisms at the origin of the solar cycle. In this paper, from various series of synoptic solar data, we identify some of the mechanisms to incorporate in a model of a two-component solar cycle. The first one concerns the dipole field which is not a surface phenomenon. We establish the cyclic behaviour and the various properties of the dipole-field sources which are deep-seated in the solar interior and have a rigid rotation of about 27 days. We identify two cyclic phenomena which, in each hemisphere, link with a 5–6-yr delay, the dipole field generation which occurs at high latitudes, to the bipolar field emergence occurring at sunspot latitudes. They are the signatures of a coupling mechanism taking place deep in the solar interior. Then we study the constraints imposed on the mechanisms of the sunspot field generation both by a two-component cycle and by new observational results. These last ones concern the links occurring between the birth of new sunspot groups and the occurrence of pre-existing features of the photospheric field and of pivot-points in rigid rotation at 27.3 days.Our final discussion is devoted to a first sketch of the distribution of the relevant mechanisms among separate regions of the convective zone. Unfortunately neither the helioseismology, nor our data analysis has yet supplied us with appropriate pieces of information for building a physical model of this two-component cycle.     

Cosmological bang as a consequence of a sudden change in the quantum statistics of nuclear matter

An heuristic hypothesis is advanced about dominant Bose statistics during the transition from the radiation era to the matter era in the early universe. It is shown that large scale Bose condensation of matter from baryon-antibaryon pairs is possible, as a result of which a colossal amount of mass may accumulate in a volume of cosmic scale. At a threshold density of matter, the structural bosons decay into the fermions of which they are composed, so that a sudden change in the symmetry of the wave functions of the particles causes a jump from Bose-Einstein to Fermi-Dirac statistics. This involves a large scale phase transition with an enormous pressure jump which may show up as a cosmological bang at the beginning of the matter era. __________ Translated from Astrofizika, Vol. 51, No. 1, pp. 161–172 (February 2008).