相关论文: Particle acceleration and dynamics of double-doubl…
Radio galaxies are episodic in nature. In our recent work, our study of jet properties and their dynamics in different episodes of activity has revealed various hitherto unknown aspects of the extragalactic jets. We discover that the…
We point out that the remarkable linearity of the ultra-steep radio spectra of high redshift radio galaxies reflects a previously reported general trend for powerful radio galaxies, according to which the spectral curvature is lesser for…
We have carried out numerical hydrodynamic simulations of radio jets from active galactic nuclei using the PLUTO simulation code, with the aim of investigating the effect of different environments and intermittency of energy injection on…
Non-radiating protons in the radio lobes have an essential role to form the jet morphology which is shown by recent radio and X-ray observations. However, since protons and electrons are not always in energy equilibrium due to weak Coulomb…
One of the striking examples of episodic activity in active galactic nuclei are the double-double radio galaxies (DDRGs) with two pairs of oppositely-directed radio lobes from two different cycles of activity. We illustrate, using the DDRG…
We present four Mpc-sized radio galaxies which consist of a pair of double-lobed radio sources, aligned along the same axis, and with a coinciding radio core. We have called these peculiar radio sources `double-double' radio galaxies (DDRG)…
We present Chandra observations of a small sample of nearby classical double radio galaxies which have more than one radio hotspot in at least one of their lobes. The X-ray emission from the hotspots of these comparatively low-power objects…
The spectral evolution of powerful double radio galaxies (FR II's) is thought to be determined by the acceleration of electrons at the termination shock of the jet, their transport through the bright head region into the lobes and the…
Taking a clue from their sharp-edged (strip-like) morphology observed in several cases, a new mechanism is proposed for the formation of the emission gaps seen between the radio lobes of many powerful extragalactic double radio sources.…
The formation mechanism of the enigmatic subclass of radio galaxies, called 'X-shaped radio galaxies' (XRGs), or 'winged' radio galaxies, which account for $\sim 10\%$ of the radio galaxy population, can be effectively constrained using the…
Relativistic and magnetised plasma ejected by radio loud AGNs through jets form the diffuse lobes of radio galaxies. The radiating particles (electron/electron-positron) in lobes emit in radio via the synchrotron process and X-ray via…
In order to understand the possible mechanisms of recurrent jet activity in radio galaxies and quasars, which are still unclear, we have identified such sources with a large range of linear sizes (220 $-$ 917 kpc), and hence time scales of…
We present results from two suites of simulations of powerful radio galaxies in poor cluster environments, with a focus on the formation and evolution of the radio lobes. One suite of models uses relativistic hydrodynamics and the other…
We investigate the correlations between spectral index, jet side and extent of the radio lobes for a sample of nearby FRII radio galaxies. In Dennett-Thorpe et al. (1997) we studied a sample of quasars and found that the high surface…
We have carried out two-dimensional, axisymmetric, hydrodynamic numerical modelling of the evolution of radio galaxy lobes. The emphasis of our work is on including realistic hot-gas environments in the simulations and on establishing what…
Double-double radio galaxies (DDRGs) offer a unique opportunity for us to study multiple episodes of jet activity in large-scale radio sources. We use radio data from the Very Large Array and the literature to model two DDRGs, B1450+333 and…
We present a model for the inverted radio spectra of active active galactic nuclei as well as the central regions of normal galaxies. The model is based on the unified scenario for active galaxies, stating that the central engines of active…
The synchrotron-radiating particles and magnetic fields in low-power radio galaxies (including most nearby cluster-centre sources), if at equipartition, can provide only a small fraction of the total internal energy density of the radio…
Using a large set of optically detected hotspots in powerful extragalactic double radio sources, we examine the basic question of whether the detection of optical synchrotron radiation requires in-situ acceleration of relativistic electrons…
In previous papers we have discussed high-resolution observations of a large sample of powerful radio galaxies with z<0.3. Jets are detected in up to 80 per cent of the sample, and radio cores in nearly all the objects; in addition, we are…