Related papers: AN IMPROVED MEASURE OF QUASAR ORIENTATION
Radio maps of AGNs often show linear features, called jets, both on pc as well as kpc scales. These jets supposedly possess relativistic motion and are oriented close to the line of sight of the observer and accordingly the relativistic…
The pulsar profile is characterised by two distinct emission components, the core and the cone. The standard model of a pulsar radio emission beam originating from dipolar magnetic fields, places the core at the centre surrounded by…
We link the lack of FR I type structure among quasars to the void of radio loud quasars below a critical disk luminosity of ~10^46 erg/sec in the PG sample. We argue that the opening angle of the obscuring torus in radio loud quasars…
{This study explores the motion of massive test particles and associated quasi-periodic oscillations (QPOs) around an accelerating black hole. The acceleration factor $A$ suppresses the radial effective potential $V_{\text{eff}}$, thereby…
We present 6-GHz Very Large Array radio images of 70 gravitational lens systems at 300-mas resolution, in which the source is an optically-selected quasar, and nearly all of which have two lensed images. We find that about in half of the…
We investigate the recent claim by Qin et al. that the observed correlations (or lack thereof) between the core dominance parameter and the core and extended powers of samples of lobe- and core-dominated quasars is in contradiction with…
We present e-MERLIN and EVN observations which reveal unambiguous jet activity within radio quiet quasar HS~0810+2554. With an intrinsic flux density of 880~nJy, this is the faintest radio source ever imaged. The findings present new…
The radio properties of 11 obscured `radio-intermediate' quasars at redshifts z>~2 have been investigated using the European Very-Long-Baseline-Interferometry Network (EVN) at 1.66 GHz. A sensitivity of ~25 micro Jy per 14x17 mas2 beam was…
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…
Compact steep spectrum (CSS) sources generally show weak Doppler boosting, yet some exceptions show multi-year-scale radio flux variability and high-energy activity. Since 2022, the CSS quasar 3C 138 has been in a radio high state…
By considering a small sample of core-dominated radio-loud quasars with X-ray jets, I show, as has been argued previously by others, that the observations require bulk jet deceleration if all of the X-ray emission is to be explained using…
We discuss the optical and radio properties of 30,000 FIRST sources positionally associated with an SDSS source in 1230 deg$^2$ of sky. The majority (83%) of the FIRST sources identified with an SDSS source brighter than r=21 are optically…
In this paper, we use multi-frequency angular size measurements of 58 intermediate-luminosity quasars reaching the redshifts $z\sim 3$ and demonstrate that they can be used as standard rulers for cosmological inference. Our results indicate…
The nature of the optical--radio correlations for powerful radio galaxies is investigated using spectroscopic observations of a complete sample of southern 2Jy radio sources. In line with previous work, we find that significant correlations…
Observations have shown that UV/optical variation amplitude of quasars depend on several physi- cal parameters including luminosity, Eddington ratio, and likely also black hole mass. Identifying new factors which correlate with the…
The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet (EUV) for the radio loud component of the quasar population (RLQs), compared to the radio quiet…
Jets of compact radio sources are highly relativistic and Doppler boosted, making studies of their intrinsic properties difficult. Observed brightness temperatures can be used to study the intrinsic physical properties of the relativistic…
Relations between the observed quantities for a beamed radio jet, apparent transverse speed and apparent luminosity (beta_app,L), and the intrinsic quantities, Lorentz factor and intrinsic luminosity (gamma,L_o), are investigated. The…
Studies show that both radio jets from the active galactic nuclei (AGN) and the star formation (SF) activity in quasar host galaxies contribute to the quasar radio emission; yet their relative contributions across the population remain…
We use photometric data, from the optical to the mm for a large sample of optically selected radio-quiet quasars, at low and high redshifts, to test emission models from circum-nuclear dusty torii around them. Model parameters, such as dust…