Related papers: Narrow [O III] emission lines as a potential proxy…

Moderate-resolution spectra of the H$\beta$--[O III] $\lambda$5007 region have been obtained for 41 radio-loud quasars in order to investigate relationships among their broad- and narrow-line profiles, radio structures, and X-ray…

Insight into quasar ages may be obtained from the proximity effect, but so far only in a limited number of bright quasars. Based on ~2600 SDSS quasar spectra at 2.5 <= z <= 3.5, a search for spectral voids between Ly-alpha forest lines…

We conduct kinematic analysis of the SDSS spectra of 568 obscured luminous quasars, with the emphasis on the kinematic structure of the [OIII]5007 emission line. [OIII] emission tends to show blueshifts and blue excess, which indicates that…

We report on 293 quasars with strong NIV] lambda 1486 or NIII] lambda 1750 emission lines (rest-frame equivalent width > 3 \AA) at 1.7 < z < 4.0 selected from the Sloan Digital Sky Survey (SDSS) Fifth Data Release. These nitrogen-rich…

In active galactic nuclei, jet-driven feedback plays a significant role in influencing the properties of gas within their host galaxy and the circumgalactic medium. By combining observations from the Very Large Array Sky Survey, the Faint…

We recently proposed the equivalent width (EW) of the narrow [OIII]5007{\AA} emission line as an orientation indicator for active galactic nuclei. We tested this method on about $12,300$ optically selected broad line quasars from the SDSS…

Nearly 300 quasars have now been found at $z >$ 6, including nine at $z >$ 7. They are thought to form from the collapse of supermassive primordial stars to 10$^4$ - 10$^5$ M$_{\odot}$ black holes at $z \sim$ 20 - 25, which then rapidly…

We undertake a quantitative investigation, using Monte Carlo simulations, of the amount by which quasars are expected to exceed radio galaxies in optical luminosity in the context of the `receding torus' model. We compare these simulations…

We present near-infrared spectra of seven radio-loud quasars with a median redshift of 2.1, five of which were previously known to have Ly alpha nebulae. Extended [OIII]5007 and H alpha emission are evident around six objects, at the level…

In this work, we revisit the relationship between [O III] line width $w_{\rm 90}$ (as the indicator of AGN outflow velocity) and the radio emission in RQQs by employing a large sample of Type I quasars ($\sim 37,000$) selected from the…

We present new spectroscopic observations of the southern radio galaxy PKS1549-79 (z =0.152).Despite the flat spectrum character of the radio emission from this source, our optical spectra show no sign of the broad permitted lines and…

We investigate the [O II] emission line properties of 18,508 quasars at z<1.6 drawn from the Sloan Digital Sky Survey (SDSS) quasar sample. The quasar sample has been separated into 1,692 radio-loud and 16,816 radio-quiet quasars (RLQs and…

(Abridged) With the largest homogeneous quasar sample with optical spectra and robust radio morphology classifications assembled to date, we investigate quasar radio and optical properties with unprecedented statistical power. The data…

We have obtained near-infrared spectroscopy of a small sample of powerful Compact Steep-Spectrum (CSS) radio sources mainly, but not exclusively, from the 3CR sample. We find no differences between the distributions in the equivalent width…

The [O III] $\lambda\lambda\ 4960,5008$ emission lines in the optical spectra of galaxies and quasars have been widely used to investigate the possible variation of the fine-structure constant $\alpha$ over cosmic time. In this work, we…

We present a study of a sample of 223 radio-loud quasars (up to redshift $<$0.3) in order to investigate their spectral properties. Twenty-six of these radio-loud quasars are identified as Flat Spectrum Radio Quasars (FSRQs) and fifty-four…

We use archival WISE and Spitzer photometry to derive optical line fluxes for a sample of distant quasars at z ~6. We find evidence for exceptionally high equivalent width [OIII] emission (rest-frame EW ~400 {\AA}) similar to that inferred…

Weak emission-line quasars (WLQs) are a subset of Type 1 quasars that exhibit extremely weak Ly$\alpha +$N V $\lambda$1240 and/or C IV $\lambda$1549 emission lines. We investigate the relationship between emission-line properties and…

We present the low-frequency radio spectra of 9 high-redshift quasars at $5.6 \leq z \leq 6.6$ using the Giant Metre Radio Telescope band-3, -4, and -5 observations ($\sim$300-1200 MHz), archival Low Frequency Array (LOFAR; 144 MHz), and…

Deep optical images have been gathered for a nearly complete sample of radio galaxies from the Revised 3rd Cambridge (3CR) Catalog in the redshift range 0.15 < z < 0.65. Total and nuclear magnitudes and colors have been extracted. The…