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101.
Saikia D. J. Shastri P. Cornwell T. J. Junor W. Muxlow T. W. B. 《Journal of Astrophysics and Astronomy》1989,10(2):203-235
As part of our study to understand the nature of extragalactic radio sources which are very asymmetric in the surface brightness
of the two lobes, often with radio emission on only one side of the nucleus, we have observed a large number of them with
high angular resolution and good surface brightness sensitivity at radio frequencies. In this paper we present VLA and MERLIN
observations of 15 such sources. We discuss their observed structures and spectra, and possible explanations for their morphologies.
We report evidence of a possible correlation between the hot-spot brightness ratio and the degree of core prominence, used
as a Statistical measure of source orientation, suggesting that relativistic beaming of the hot-spot emission does play a
significant role in the observed brightness asymmetry. To explain the apparently one-sided sources within the relativistic
beaming framework, the velocities required are in the range of 0.2 to 0.8c. We discuss the possibility that the lobe which is seen to the south of the jet in 3C273 is the counter-lobe seen in projection.
We also draw-attention to a number of one-sided sources with very weak cores, and discuss their possible nature. 相似文献
102.
103.
在浙西北双溪坞群和上墅组火山岩系获得较可靠的Sm-Nd同位素年龄的基础上,本文进一步做了Nd、Sr同位素地球化学研究。∈Nd(T)和∈Sr(T)示踪判别了该区前震旦纪火山岩浆源区特征及其物质来源。同时,Nd同位素模式年龄为该区存在更古老基底提供了重要的地质年代信息。 相似文献
104.
Zhi-qiang Shen Tong-shan Wan Xiao-yu Hong Dong-rong Jiang Shi-guang Liang 《Chinese Astronomy and Astrophysics》1996,20(4):415-425
This paper describes a 5 GHz VLBI survey in the southern hemisphere. The first observation of 23 extragalactic radio sources was conducted in November 1992. Twenty VLBI images were obtained, of which 15 sources show core-jet structure, one has a two-sided jet, and three sources are unresolved. No compact double source was found. Eleven of the 16 sources with core-jet (including a two-aided jet) show evidence of jet bending. In addition, four sources appear to be superluminal, of which three sources are new. 相似文献
105.
K. A. Postnov 《Astronomy Letters》2003,29(6):372-373
The empirically found universal power-law form of the X-ray luminosity function for a population of high-mass X-ray binaries in galaxies can be explained by the fundamental mass-luminosity and mass-radius relations for massive stars. 相似文献
106.
We have reinvestigated the reported tendency for the extended radio structures associated with bright elliptical galaxies
to be oriented preferentially along the optical minor axes. It is found that such a tendency exists only for those galaxies
in which the compact radio cores coincident with their nuclei are quite prominent. If the galaxies are divided into two groups
according to whether their cores account for less than or greater than 10 per cent of the total flux density at 2.7 GHz, the
angle Φ (between the radio axis and the optical minor axis) appears to be uniformly distributed between 0‡ and 90‡ for the
former, but is nearly always < 30‡ for the latter group. One possible explanation is that the radio emission from compact
cores suffers thermal absorption by ionized gas that is distributed differently in the two groups. 相似文献
107.
F. Mantovani M. Nanni C. J. Salter P. Tomasi 《Journal of Astrophysics and Astronomy》1982,3(3):335-350
New observations of six fields from the low galactic latitude BG survey are presented. The radio sources within each of these
fields appear to be of a predominantly extragalactic nature. However, one object is in close positional proximity to the pulsar
1922 + 20 and the possibility of their association is considered. The extended source BGE 0323 + 65 is shown to be unlikely
to exist. 相似文献
108.
LIU Feng HU Fei & ZHU Jiang . College of Environmental Sciences Peking University Beijing China . LAPC Institute of Atmospheric Physics Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2005,48(8):1270-1279
The deterioration of air quality is threatening the life and health of people. Scientists in China and other countries have done a great deal of research work on the details of air pollution and the methods of preven-tion and control during the past decades. Up to now, most of the achievements are concentrated on the techniques of controlling pollutant sources and the programs of reduction, which focus on the improve-ment of air quality and the restoration of environment. The techniques of con… 相似文献
109.
Having analyzed high-resolution observations of extragalactic compact radio sources with modern systems of radio telescopes, we obtained an estimate of the upper limit for the photon electric charge, eγ ? 3×10?33 of the elementary charge (assuming the photon charge to be energy independent). This is three orders of magnitude better than the limit obtained from radio pulsar timing. We also set a limit on the charge of a gamma-ray (energy ~0.1 MeV) photon. In the future, the estimate based on extragalactic sources can be improved significantly. 相似文献
110.
Using a large sample of 78 well-observed double quasars, we have investigated several consequences of the relativistic beaming
model. In this model the ratio of the strengths of the central component and outer lobes of a double source depends on whether
the jet axis lies close to or away from the line of sight, If this is the actual situation, the fraction of emission from
the core,f
c, may be used as a statistical measure of the orientation of the source and should be correlated with other source parameters
which also depend on the inclination of the jet axis to the line of sight.
We findf
c to be anticorrelated with the overall projected linear size of the extended emission but to exhibit a positive correlation
with both the observed degree of misalignment from a collinear double structure, and the ratio of separations of the outer
hotspots from the central component. As might be expected from these relationships, we also find sources of smaller projected
linear sizes to appear more misaligned and the degree of misalignment to be correlated with the ratio of separations of the
outer hotspots. All these correlations are consistent with the predictions of the relativistic beaming model. 相似文献