Spectral Indices of Core and Extended Components of Extragalactic Radio Sources

We use observed peak and total flux densities at 6cm and 20cm to determine the spectral indices separately for the core and extended components of QSOs and galaxies, as well as their core-dominance parameters. Our results indicate that 1) Nine QSOs show both greater than 1.0 core-dominance parameters (those objects should be blazars) and greater than 0.5 spectral indices. The average core spectral index is αCore = 0.85±0.21 for the nine blazars, which implies that it is not reliable to use αradio = 0.0 for blazars. For the different subclasses, the core and extended spectral indices are as follows: for the blazars, αCore = 0.22±0.06 and αExt =0.77±0.12; the galaxies,αCore = 1.01±0.13 and αExt =0.83±0.21, and for the QSOs, αCore = 0.28±0.10 and αExt =0.68±0.08. 2) The core spectral index and core dominance parameter (R) show an anti-correlation, αC = (-1.28±0.26) log R+ (0.65 ± 0.11); 3) R is approximately linearly correlated with redshift (z).     

An X-Ray Study of Lobe-Dominated Radio-Loud Quasars with XMM-Newton

We report on our results of X-ray spectral analysis for a sample of radio-loud quasars covering a wide range of the radio core-dominance parameter, R, from core-dominated to lobe-dominated objects, using data obtained mostly with the XMM-Newton Observatory. We find that the spectral shape of the underlying power-law continuum is flat even for the lobe-dominated objects (average photon index ～ 1.5), indistinguishable from that of core-dominated quasars. For lobe-dominated objects, contribution of X-rays from the jets is expected to be very small based on previous unification schemes, more than one order of magnitude lower than the observed X-ray luminosities. Assuming that radio-loud quasars follow the same X-ray-UV/optical luminosity relation for the disk-corona emission as found for radio-quiet quasars, we estimate the X-ray flux contributed by the disk-corona component from the optical/UV continuum. We find that neither the luminosity, nor the spectral shape, of the disk-corona X-ray emission can account for the bulk of the observed X-ray properties. Thus in lobe-dominated quasars, either the disk-corona X-ray emission is much enhanced in strength and flatter in spectral shape (photon index～1.5) compared to normal radio-quiet quasars, or their jet X-ray emission is much enhanced compared to their weak radio core-jet emission. If the latter is the case, our result may imply that the jet emission in X-rays is less Doppler beamed than that in the radio. As a demonstrating example, we test this hypothesis by using a specific model in which the X-ray jet has a larger opening angle than the radio jet.     

河外射电源变化的观测研究

在本文中评述河外射电源变化的观测进展。首先对几个射电变源的一些专门术语和定义作介绍。然后叙述在整个频谱上各种变化测量的结果，包括流量、频谱和偏振的变化。讨论了ＶＬＢＩ对变化研究的重要影响。简要地触及短时标变化引发的逆康普顿灾变的理论问题，最后，强调指出了多波段同时观测河外射电源在深入了解活动星系核方面的重要作用。     

Correlation between the Directions of the Magnetic Fields and Major Axes of Extragalactic Radio Sources

The distribution of relative position angles between the integrated intrinsic polarization (perpendicular to the direction of the intrinsic magnetic field) and the major axis of an extragalactic radio source were studied for different types of radio sources. Data for 280 extragalactic radio sources were used and it was found that there are large differences in the relative orientation of different types of radio sources. The directions of the intrinsic integrated magnetic fields correlate with the major radio axes of more elongated radio sources (K > 2.5, where K is the ratio of lengths of the major and minor axes of the radio images) and for radio sources of type FR II, whereas for less elongated objects (K < 2.5) and for radio sources of type FR I the magnetic fields do not correlate at all with the radio axes. An alternative mechanism for the formation of a radio galaxy from relativistic plasma ejected from the central part of an optical galaxy and moving in its large-scale, dipole magnetic field may be a theoretical basis for classification with respect to the elongation parameter K of the radio image.     

Broad Iron Lines in AGN and X-Ray Binaries

Several AGN and black hole X-ray binaries show a clear very broad iron line, which is strong evidence that the black holes are rapidly spinning. Detailed analysis of these objects shows that the emission line is not significantly affected by absorption and that the source variability is principally due to variation in amplitude of a power-law. Underlying this is a much less variable, relativistically-smeared, reflection-dominated, component which carries the imprint of strong gravity at a few gravitational radii. The strong gravitational light bending in these regions then explains the power-law variability as due to changes in height of the primary X-ray source above the disc. The reflection component, in particular its variability and the profile of the iron line, enables us to study the innermost regions around an accreting, spinning, black hole.     

ISS of Polarized Compact Extragalactic Radio Sources

It is shown that the detailed inter-relations of the 8.6 GHz IDV in Stokes' parameters I, Q and U of the quasar 0405–385, as quantified by their auto and cross correlations, can be successfully modelled by interstellar scintillation (ISS) of a double source with two components separated by about 10 micro-arcseconds. Though this is not a unique source model it confirms that ISS can explain quantitatively the rapid variations in both flux and linear polarization. Thus there is no evidence in support of an intrinsic component in the IDV. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the Asymmetries in Powerful Extragalactic Radio Sources

We have investigated the correlations between the asymmetries in depolarization and spectral index in a bright source sample. We find a significant correlation between these asymmetries which can be understood in terms of the relativistic beaming hypothesis in which the counter jet side is steeper and more polarized than the jet side due to the presence of a halo of hot gas surrounding the source and contribution from the beamed jet and hot spot emission to the observed lobe emission. This simple interpretation is however complicated by the presence of a stronger correlation between these parameters and extended luminosity which is expected to be aspect-invariant; suggesting that the observed spectral index – depolarization correlation is an artefact of their being separately correlated with radio luminosity. This revised version was published online in July 2006 with corrections to the Cover Date.     

An Infrared Photometric Study of Galaxies with Extragalactic H2O Maser Sources

All galaxies with extragalactic H_2O maser sources observed so far are collected. With the 2MASS and the IRAS photometric data an infrared study is performed on those galaxies.By a comparison between the H_2O maser detected sources and non-detected sources in the infrared it is indicated that infrared properties in the IRAS 12-25μm and 60-100μm are important for producing H_2O masers in galaxies.It is also found that the H_2O maser galaxies with different nuclear activity types have rather different infrared properties mainly in the IRAS 12-60μm region.     

Annual Modulation in Intraday Variability Timescales of Extragalactic Radio Sources

Annual modulations in timescales of intraday variability (IDY here-after) are discussed for six extragalactic sources:0716 714,0917 624,0954 65,1749 70,1803 78 and 2007 77.The timescales calculated from scintillation the-ory are compared with the observational data.It is emphasized that systematic observations are required to identify the phenomenon and to determine the motion of the interstellar medium with respect to the Local Standard of Rest.In addi-tion,significant deviations from the annual modulation could be due to intrinsic variations.     

三颗河外射电源第一历元的VLBI图像

本文给出利用上海、乌鲁木齐、意大利ＮＯＴＯ和南非ＨａｒｔＲＡＯ射电望远镜,对三颗河外射电源（１５３２＋０１６,２３２００２０,２３５１１５４）,在５ＧＨｚ频率上的第一历元ＶＬＢＩ观测成图结果     

高频VLBI观测射电源的结构

高频VLBI观测揭示出河外射电源在pc或者亚pc尺度上大都有核-喷流的内部结构。尤其是对平谱致密射电源中毫角秒尺度的子源，能以相当高的概率观测到它的视超光速现象。多频观测可监测到一些新喷流子源的出现，特别在射电激变源中这些新喷流子源的出现与宽带内(从光学到γ射线)的爆发相关。且得到的一些源的核区谱指数分布，为确认源的VLBI核提供了支持。     

河外H2O超脉泽源及与其相关的分子谱线的观测和研究

自从在活动星系核NGC4945的视线方向上发现第一个河外H2O超脉泽源以来，迄今为止已发现了19个河外H2O超脉泽源，对与活动星系核成协和河外H2O超脉泽源及分子谱线的观测和研究是探测和研究活动星系核核区中央源，拱核气体和尘埃环性质的非常有效的工具，主要评述对河外H2O超脉泽源及与其相关分子谱线的搜索，观测和理论研究现状。     

Spectral Monitoring of AGN at the 6 Meter Telescope

Spectral monitoring of NGC 3516, NGC 4151, NGC 5548 and NGC 7469 has been carried out in 1986-1996 on time scales of days-months-years. In 1986-1995, the observations were made on the SAO 6-m telescope using a TV scanner with SNR about 20 in the range 4000-5200 Å (about 500 spectra). In 1996, virtually all spectra were obtained using a CCD camera with 2D and 3D spectrographs in the range 4000-7000 Å with SNR 50-100 (270 spectra). The Seyfert galaxies NGC 7469, NGC 5548, and 3C390.3 were observed in the international "AGN Watch" program by about 40 observatories around the world at optical wavelengths and by the IUE and HST in the UV. Our observations in this program demonstrated that there are no significant radial motions inside the broad line regions in NGC 4151, 3C390.3 and, possibly, in NGC 5548; that the BLR dimensions are about half those previously assumed; and that there is stratification of the BLR. The SAO 6-m observations suggest the existence of narrow satellites of the H lines during the low state of NGC 4151 in 1986-1987; new data on the narrow line region indicates the existence of an intermediate-velocity OIII component (about 2000 km/s).     

Similarities between Circular Polarization in Galactic Jet Sources and AGN

We compare the observational properties of the circular polarization in Galactic jet sources with that observed in AGN, and outline the constraints they place on the mechanism responsible for the circular polarization. We also discuss the implications of the time scale of polarization variations on the mechanism responsible for the circular polarization.     

Theoretical Models for Producing Circularly Polarized Radiation in Extragalactic Radio Sources

We discuss the production of circular polarization in compact radio sources both by the intrinsic mechanism and by Faraday conversion. We pay particular attention to the magnetic field structure, considering partially ordered fields and Laing sheets, and distinguishing between uniform and unidirectional fields. (The latter can be constrained by flux conservation arguments.) In most cases, Faraday conversion is the more important mechanism. Conversion operates on Stokes U, which can be generated by internal Faraday rotation, or by magnetic field fluctuations, which can therefore produce circular polarization even in a pure pair plasma. We also show that the spectrum of circular polarization in an inhomogeneous jet can be quite different from that in a uniform source, being flat or even inverted.     

南天区20个河外射电源的VLBI研究

本文报道南天区5GHzVLBI普查式观测结果．首次观测是在1992年11月期间进行的，共观测了23个河外射电源，获得了20个河外射电源的VLBI高分辨率的射电图象．有15个射电源呈现核喷流结构，1个有双向喷流，3个未分解，末发现有致密观源．在16个核喷流（包括一个双向喷流源）源中有11个呈现弯曲喷流现象．此外还首次发现有3个源中可能有超光速运动现象．     

An Examination of Candidate AGN Counterparts to Unidentified EGRET Sources

Radio observations of candidate active galactic nucleus counterparts to eight EGRET sources with |b| > 9^∘ are examined, and several new identifications suggested. Preference is given to the use of all-sky, flux-density limited surveys in searching for counterparts and attention is drawn to the importance of not relying exclusively on spectral indices inferred from single-dish observations.     

Ellipticity of Nearby Elliptical Galaxies Identified with Extended Extragalactic Radio Sources

The dependence of the ellipticity of nearby optical galaxies associated with extragalactic radio sources on the type of radio galaxy is considered. It is shown that elliptical galaxies identified with radio galaxies of the FRI type and with radio sources having a radio image with a small elongation have a smaller ellipticity, on the average, than those associated with radio galaxies of the FRII type and with radio sources with greater elongation. As one possible explanation for this phenomenon, one can assume that the optical galaxies associated with radio galaxies of type FRI and with radio sources of small elongation are oriented in space so that they are observed edge-on relatively rarely.     

Circular Polarization Variability in Extragalactic Sources on Time Scales of Months to Decades

We present previously unpublished circular polarization (cp) measurements at 4.8 and 8.0 GHz made with the University of Michigan 26-meter prime focus telescope during 1978–1984 and results of a new observational program during the past two years. Based on the preliminary analysis of our recent data, eight sources were detected at 4.8 GHz with average degrees of cp ranging from ≤ 0.1% to ≥ 1%.The results are compared with observations at other frequencies and with linear polarization and total flux density variability in the sources. The behavior of the cp variability observed to date is consistent with stochastic variations produced by mode conversion in transient, opaque emitting regions in the sources. The observed sign changes observed between different epochs and different frequencies are not consistent with the hypothesis that sources maintain a fixed handedness of cp.