共查询到20条相似文献，搜索用时 31 毫秒
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We used the VLBA(NRAO, USA) and made VLBI observations towards the compact steep spectrum sources 3C43, 3C48 and 3C454 at the central frequency 1.6 GHz, and obtained their total flux density maps and information on the structures of their components. By comparison with the previous data, we analyzed the variations of their flux densities as well as the displacements of their components. It is found that the total flux density of the source 3C43, as well as the flux densities and relative positions of its components are quite stable in 14 years. For the source 3C454, the total flux density and the flux densities of its components are also relatively stable, but two of the components moved away from the central core with superluminal velocities of 21.6c and 17.7c. Fitted to their flux densities at 4 L-band frequencies, the spectral indexes of the sources 3C43 and 3C454 were obtained to be 0.63 and 0.86, respectively, in good agreement with previous results, and consistent with the definition of α ≥0.5 for compact steep spectrum sources. 相似文献
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D. Tansley M. Birkinshaw M. J. Hardcastle D. M. Worrall 《Monthly notices of the Royal Astronomical Society》2000,317(3):623-629
We present images of infrared (IR) emission from the radio jet in 3C 66B. Data at three wavelengths (4.5, 6.75 and 14.5 μm) were obtained using the Infrared Space Observatory . The 6.75-μm image clearly shows an extension aligned with the radio structure. The jet was also detected in the 14.5-μm image, but not at 4.5 μm. The radio–infrared–optical spectrum of the jet can be interpreted as synchrotron emission from a population of electrons with a high-energy break of 4×1011 eV. We place upper limits on the IR flux from the radio counter-jet. A symmetrical, relativistically beamed twin-jet structure is consistent with our results if the jets consist of multiple components. 相似文献
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J. H. Croston M. J. Hardcastle M. Birkinshaw D. M. Worrall 《Monthly notices of the Royal Astronomical Society》2003,346(4):1041-1054
We present new XMM–Newton observations of the hot-gas environments of two low-power twin-jet radio galaxies, 3C 66B and 3C 449, showing direct evidence for the interactions between X-ray-emitting gas and radio plasma that are thought to determine the large-scale radio structure of these sources. The temperatures that we measure for the two environments are significantly higher than those predicted by standard luminosity–temperature relations for clusters and groups. We show that luminosity–temperature relations for radio-quiet and radio-loud X-ray groups differ, in the sense that radio-source heating may operate in most groups containing radio galaxies. If the radio lobes are expanding subsonically, we find minimum ages of 3 × 108 yr for 3C 66B, and 5 × 108 yr for 3C 449, older than the values obtained from spectral ageing, which would give the radio source sufficient time to heat the groups to the observed temperatures for plausible values of the jet power. The external pressures in the atmospheres of both radio galaxies are an order of magnitude higher than equipartition estimates of their radio-lobe pressures, confirming that the radio lobes either are out of equipartition or require a pressure contribution from non-radiating particles. Constraints from the level of X-ray emission we measure from the radio lobes allow us to conclude that a departure from equipartition must be in the direction of magnetic domination, and that the most plausible candidates for a particle contribution to lobe pressure are relativistic protons, an additional population of low-energy electrons, or entrained and heated thermal material. 相似文献
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P. Thomasson D. J. Saikia T. W. B. Muxlow 《Monthly notices of the Royal Astronomical Society》2006,372(4):1607-1613
Multifrequency, high-resolution radio observations of the quasar 3C 254 using the Multi-Element Radio-linked Interferometer Network (MERLIN) are presented. The quasar has a highly asymmetric radio structure, with the eastern component of the double-lobed structure being much closer to the nucleus and significantly less polarized than the western one. However, the two lobes are more symmetric in their total flux densities. The observations show the detailed structure of the hotspots which are very different on opposite sides of the radio core, reveal no radio jet and suggest that the oppositely directed jets may be intrinsically asymmetric. 相似文献
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Mark Lacy Steve Rawlings Katherine M. Blundell & Susan E. Ridgway 《Monthly notices of the Royal Astronomical Society》1998,298(4):966-976
Multiwavelength imaging and spectroscopy of the z =0.708 radio galaxy 3C 441 and a red aligned optical/infrared component are used to show that the most striking aspect of the radio–optical 'alignment effect' in this object is due to the interaction of the radio jet with a companion galaxy in the same group or cluster. The stellar population of the red aligned continuum component is predominantly old, but with a small post-starburst population superposed, and it is surrounded by a low-surface-brightness halo, possibly a face-on spiral disc. The [O iii ] 500.7/[O ii ] 372.7 emission-line ratio changes dramatically from one side of the component to the other, with the low-ionization material apparently having passed through the bow shock of the radio source and been compressed. A simple model for the interaction is used to explain the velocity shifts in the emission-line gas, and to predict that the ISM of the interacting galaxy is likely to escape once the radio source bow shock has passed through. We also discuss another, much fainter, aligned component, and the subarcsecond-scale alignment of the radio source host galaxy. Finally, we comment on the implications of our explanation of 3C 441 on theories for the alignment effect. 相似文献
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Inverse Compton X-rays from the radio galaxy 3C 219 总被引：1，自引：0，他引：1
A. Comastri G. Brunetti D. Dallacasa M. Bondi M. Pedani G. Setti 《Monthly notices of the Royal Astronomical Society》2003,340(4):L52-L56
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Dynamical models for jet deceleration in the radio galaxy 3C 31 总被引：1，自引：0，他引：1
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Anisotropic inverse Compton emission in the radio galaxy 3C 265 总被引：1，自引：0，他引：1
M. Bondi G. Brunetti A. Comastri G. Setti 《Monthly notices of the Royal Astronomical Society》2004,354(3):L43-L47
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We present deep near-infrared images, taken with the Subaru Telescope, of the region around the z =1.08 radio source 3C 356 which show it to be associated with a poor cluster of galaxies. We discuss evidence that this cluster comprises two subclusters traced by the two galaxies previously proposed as identifications for 3C 356, which both seem to harbour active galactic nuclei, and which have the disturbed morphologies expected if they underwent an interpenetrating collision at the time the radio jets were triggered. We explain the high luminosity and temperature of the diffuse X-ray emission from this system as the result of shock heating of intracluster gas by the merger of two galaxy groups. Taken together with the results on other well-studied powerful radio sources, we suggest that the key ingredient for triggering a powerful radio source, at least at epochs corresponding to z ∼1 , is a galaxy–galaxy interaction which can be orchestrated by the merger of their parent subclusters. This provides an explanation for the rapid decline in the number density of powerful radio sources since z ∼1 . We argue that attempts to use distant radio-selected clusters to trace the formation and evolution of the general cluster population must address ways in which X-ray properties can be influenced by the radio source, both directly, by mechanisms such as inverse Compton scattering, and indirectly, by the fact that the radio source may be preferentially triggered at a specific time during the formation of the cluster. 相似文献
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M. J. Hardcastle 《Monthly notices of the Royal Astronomical Society》1998,298(2):569-576
I present 1.5- and 8.4-GHz observations with all configurations of the NRAO VLA of the wide-angle tail source 3C 130. The source has a pair of relatively symmetrical, well-collimated inner jets, one of which terminates in a compact hotspot. Archival ROSAT PSPC data confirm that the environment of 3C 130 is a luminous cluster with little sign of sub-structure in the X-ray-emitting plasma. I compare the source to other wide-angle tail objects and discuss the properties of the class as a whole. None of the currently popular models is entirely satisfactory in accounting for the disruption of the jets in 3C 130. 相似文献
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Chris Simpson Steve Rawlings 《Monthly notices of the Royal Astronomical Society》2000,317(4):1023-1028
We present JHKL ' photometry of a complete sample of steep-spectrum radio-loud quasars from the revised 3CR catalogue in the redshift range 0.65 z <1.20. After correcting for contributions from emission lines and the host galaxies, we investigate their spectral energy distributions (SEDs) around 1 μm. About 75 per cent of the quasars are tightly grouped in the plane of optical spectral index, α opt , versus near-infrared spectral index, α IR , with the median value of α opt close to the canonical value, and the median α IR slightly flatter. We conclude that the fraction of moderately obscured, red quasars decreases with increasing radio power, in accordance with the 'receding torus' model which can also explain the relatively flat median near-infrared spectra of the 3CR quasars. Two of the red quasars have inverted infrared spectral indices, and we suggest that their unusual SEDs might result from a combination of dust-scattered and transmitted quasar light. 相似文献
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S.W. Allen G.B. Taylor P.E.J. Nulsen R.M. Johnstone L.P. David S. Ettori A.C. Fabian W. Forman C. Jones B. McNamara 《Monthly notices of the Royal Astronomical Society》2001,324(4):842-858
We examine the properties of the X-ray gas in the central regions of the distant ( z =0.46) , X-ray luminous cluster of galaxies surrounding the powerful radio source 3C 295, using observations made with the Chandra Observatory . Between radii of 50 and 500 kpc, the cluster gas is approximately isothermal with an emission-weighted temperature, kT ∼5 keV . Within the central 50-kpc radius this value drops to kT ∼3.7 keV . The spectral and imaging Chandra data indicate the presence of a cooling flow within the central 50-kpc radius of the cluster, with a mass deposition rate of approximately 280 M⊙ yr−1 . We estimate an age for the cooling flow of 1–2 Gyr , which is approximately 1000 times older than the central radio source. We find no evidence in the X-ray spectra or images for significant heating of the X-ray gas by the radio source. We report the detection of an edge-like absorption feature in the spectrum for the central 50-kpc region, which may be caused by oxygen-enriched dust grains. The implied mass in metals seen in absorption could have been accumulated by the cooling flow over its lifetime. Combining the results on the X-ray gas density profile with radio measurements of the Faraday rotation measure in 3C 295, we estimate the magnetic field strength in the region of the cluster core to be B ∼12 μG . 相似文献
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Lei Liu Institute of Particle Physics Huazhong Normal University Wuhan 《中国天文和天体物理学报》2006,6(6):663-668
Some nonlinear dynamical techniques, including state-space reconstruction and correlation integral, are used to analyze the light curve of 3C 273. The result is compared with a chaotic model. The similarities between them suggest there is a low-dimension chaotic attractor in the light curve of 3C 273. 相似文献