1,220 datasets found

We use mid-infrared (MIR) spectroscopy of unobscured active galactic nuclei (AGNs) to reveal their native dusty environments. We concentrate on Seyfert 1 galaxies, observing a...

We examine the ultraviolet and X-ray properties of 256 radio-quiet Sloan Digital Sky Survey quasars (QSOs) observed in X-rays with Chandra and/or XMM-Newton in order to study...

We present Chandra observations of nine high-redshift quasars (z=2.7-5.9) discovered by the Sloan Digital Sky Survey with weak or undetectable high-ionization emission lines in...

We present the clustering of Deep Extragalactic Evolutionary Probe 2 (DEEP2) galaxies at 0.7<z<1.4 around quasars identified using both the Sloan Digital Sky Survey (SDSS)...

With close pairs of quasars at different redshifts, a background quasar sight line can be used to study a foreground quasar's environment in absorption. We search 149...

We present a measurement of the D/H abundance ratio in a metal-poor damped Ly{alpha}(DLA) system along the sight line of QSO SDSS 1558-0031.

We present abundance measurements for two super-Lyman limit systems (SLLSs; quasar absorption-line systems with 10^19^cm^-2^<N_HI_<10^20.3^cm^-2^) selected from a set of...

We examine the variability of the high-ionization CIV {lambda}1549 line in a sample of 105 quasars observed at multiple epochs by the Sloan Digital Sky Survey. We find a strong...

We study the properties of infrared-selected QSOs (IR QSOs), optically selected Palomar-Green QSOs (PG QSOs), and narrow-line Seyfert 1 galaxies (NLS1s). We compare their...

Using an empirical relation between the broad-line region size and optical continuum luminosity, we estimated the black hole mass and accretion rate for 135 active galactic...

We discuss the statistics of projection on the sky of a simple model for radio sources. The model has a core and two hot spots at unequal distance with an overall structure...

The Snapshot Survey was a search for cases of gravitational lensing among intrinsically-luminous, high-redshift quasars using the Hubble Space Telescope (HST) Planetary Camera...

We present and make publicly available the third data release (DR3) of the Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) survey. KODIAQ DR3 consists of...

We present and make publicly available the first data release (DR1) of the Keck Observatory Database of Ionized Absorption toward Quasars (KODIAQ) survey. The KODIAQ survey is...

From the measurement on the Digitized Sky Survey of the optical position of 153 QSOs with an accurate VLBI position, we have determined that the r.m.s. uncertainties of these...

In this work, we assess the combined use of Gaia photometry and astrometry with infrared data from CatWISE in improving the identification of extragalactic sources compared to...

We report periodic oscillations in the 15-year-long optical light curve of the gravitationally lensed quasar J0158-4325 at z_s_=1.29. The signal is enhanced during a high...

We present six new time-delay measurements obtained from Rc-band monitoring data acquired at the MPIA 2.2m telescope at La Silla observatory between October 2016 and February...

We present the first results of a project called SAGAN, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the Universe, called giant...

We present a new catalogue of ~2400 optically selected quasars with spectroscopic redshifts and X-ray observations from either Chandra or XMM-Newton. The sample can be used to...