Related papers: X-ray Absorption of High Redshift Quasars

Outflows of photoionized gas are commonly detected in the X-ray spectra of Seyfert 1 galaxies. However, the evidence for this phenomenon in broad line radio galaxies, which are analogous to Seyfert 1 galaxies in the radio-loud regime, has…

We explore the connection between absorption by neutral gas and extinction by dust in mid-infrared (IR) selected luminous quasars. We use a sample of 33 quasars at redshifts 0.7 < z < 3 in the 9 deg^2 Bo\"otes multiwavelength survey field…

Using a hydrodynamic simulation of a LCDM universe, we investigate the "X-ray forest" absorption imprinted on the spectra of background quasars by the intervening intergalactic medium (IGM). In agreement with previous studies, we find that…

We present MeerKAT observations searching for HI absorption in a sample of 17 powerful ($L_{\rm 1.4GHz}> 10^{27}$ W Hz$^{-1}$) radio sources at intermediate redshifts ($0.25<z<0.7$). The sample is well characterised at radio and optical…

Enhanced ionizing radiation in close proximity to redshift $z\gtrsim 6$ quasars creates short windows of intergalactic Ly$\alpha$ transmission blueward of the quasar Ly$\alpha$ emission lines. The majority of these Ly$\alpha$ near-zones are…

We have obtained low resolution (~20 Angstrom FWHM) slit spectra of 10 quasar candidates located within one degree of the z = 2.181 quasar Q0122-380 with the objective of searching for signs of large scale structure matching the intervening…

We report the first comparative study of strong MgII absorbers seen towards radio-loud quasars of core-dominated (CDQs) and lobe-dominated (LDQs) types and normal QSOs. The MgII associated absorption systems having a velocity offset v <…

Luminous $z\ge7$ quasars provide direct probes of the evolution of supermassive black holes (SMBHs) and the intergalactic medium (IGM) during the epoch of reionization (EoR). The Ly$\alpha$ damping wing absorption imprinted by neutral…

We present a catalog of 792 DR5 SDSS quasars with optical spectra that have been observed serendipitously in the X-rays with the \emph{XMM-Newton}. These quasars cover a redshift range of z = 0.11 - 5.41 and a magnitude range of i =…

We examine the kinematics of the gas in the environments of galaxies hosting quasars at $z\sim2$. We employ 148 projected quasar pairs to study the circumgalactic gas of the foreground quasars in absorption. The sample selects foreground…

We present mid-infrared observations of 18 sources from a sample of 21 z~2 radio-intermediate obscured quasars. The mid-infrared spectra of the sources are continuum dominated, and 12 sources show deep silicate absorption with tau_9.7~1-2.…

We report spectral, imaging, and variability results from four new XMM-Newton observations and two new Chandra observations of high-redshift (z > 4) radio-loud quasars (RLQs). Our targets span lower, and more representative, values of radio…

Luminous distant quasars are unique probes of the high redshift intergalactic medium (IGM) and of the growth of massive galaxies and black holes in the early universe. Absorption due to neutral Hydrogen in the IGM makes quasars beyond a…

We present 0.5-8.0 keV Chandra observations of six bright quasars that represent extrema in quasar emission-line properties -- three quasars each with small and large blueshifts of the CIV emission line with respect to the systemic redshift…

We calculate the absorption of 10-500 GeV gamma-rays at high redshifts. This calculation requires the determination of the high-redshift evolution of the intergalactic starlight photon field, including its IR-UV spectral energy…

We present the results of an investigation into the X-ray properties of radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). We combine large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with archival…

We present initial results from the first systematic survey for MgII quasar absorption lines at z > 2.5. Using infrared spectra of 46 high-redshift quasars, we discovered 111 MgII systems over a path covering 1.9 < z < 6.3. Five systems…

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…

We report on Chandra and XMM-Newton observations of a sample of 13 quasars at z~4.7-5.4 mostly taken from the Sloan Digital Sky Survey (SDSS). The present sample complements previous X-ray studies of z>4 quasars, in which the majority of…

Abundances of galaxies at redshifts z > 4 are difficult to obtain from damped Ly {\alpha} (DLA) systems in the sightlines of quasars (QSOs) due to the Ly {\alpha} forest blanketing and the low number of high-redshift quasars detected.…