Related papers: Why Do Compact Active Galactic Nuclei at High Reds…

The study of the dominant population of high redshift IR-luminous galaxies (10^11 - 10^12 Lsun at 1<z<3), requires observation of sources at the ~0.1 mJy level in the mid-IR. We present the deepest spectra taken to date with the Infrared…

We constrain the number density and evolution of Compton-thick Active Galactic Nuclei (AGN). In the local Universe we use the wide area surveys from the Swift and INTEGRAL satellites, while for high redshifts we explore candidate selections…

The quasar 0917+624 has been one of the best studied intraday variable (IDV) radio sources. However, debate continues as to whether the underlying cause is intrinsic or extrinsic. Much previous work has assumed the IDV to be intrinsic and…

The study of Active Galactic Nuclei (AGNs) is vital in order to understand their respective nuclei bounded activity primarily triggered by the accretion disk and the associated corona. The hard X-ray emission characterised by the spectral…

We take advantage of the rich multi-wavelength data available in the Chandra Deep Field South (CDF-S), including the 4 Msec Chandra observations (the deepest X-ray data to date), in order to search for heavily-obscured low-luminosity AGN…

Active galactic nuclei (AGN) are thought to play a critical role in shaping galaxies, but their effect on the circumgalactic medium (CGM) is not well studied. We present results from the COS-AGN survey: 19 quasar sightlines that probe the…

We describe a search for molecular absorption at millimetre wavelengths associated with dusty molecular tori in active galactic nuclei (AGN). The sample observed consists of 11 flat-spectrum radio sources known to have red optical to…

Powerful extended radio galaxies in the 3CR survey are observed out to redshifts of about 2. For redshifts greater than about 0.3, the average lobe-lobe size of the sources decreases monotonically with redshift for all reasonable…

We perform long-term ($\approx 15$ yr, observed-frame) X-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6 Ms $Chandra$ Deep Field-South (CDF-S) survey; the majority are in the redshift range of…

We have carried out model calculations of the photoionized intergalactic medium (IGM) to determine the effects on the predicted ionic column densities due to uncertainties in the published dielectronic recombination (DR) rate coefficients.…

We investigate the fraction of z ~ 0.3 Lyman alpha emitting galaxies (LAEs) which host active galactic nucleus activity, which is typically from 1 - 5% at 2 < z < 6. Using optical spectroscopy of 23 LAEs at 0.2 < z < 0.45 selected with…

The maximum number density of Active Galactic Nuclei (AGNs), as deduced from X-ray studies, occurs at z<~1, with lower luminosity objects peaking at smaller redshifts. Optical studies lead to a different evolutionary behaviour, with a…

The properties of the host galaxies of a well-defined sample of 2215 radio-loud AGN with redshifts 0.03 < z < 0.3, defined from the SDSS, are investigated. These are predominantly low radio luminosity sources, with 1.4GHz luminosities of…

We describe the Carnegie-Spitzer-IMACS (CSI) Survey, a wide-field, near-IR selected spectrophotometric redshift survey with the Inamori Magellan Areal Camera and Spectrograph (IMACS) on Magellan-Baade. By defining a flux-limited sample of…

We present detailed observations of photoionization conditions and galaxy kinematics in eleven z$=1.39-2.59$ radio-loud quasar host galaxies. Data was taken with OSIRIS integral field spectrograph (IFS) and the adaptive optics system at the…

We report a sizable class of type 1 active galactic nuclei (AGNs) with unusually weak near-infrared (1-3{\mu}m) emission in the XMM-COSMOS type 1 AGN sample. The fraction of these "hot-dust-poor" AGNs increases with redshift from 6% at…

Previous surveys for HI 21-cm absorption in z > 0.1 radio galaxies and quasars yield a 40% detection rate, which is attributed to unified schemes of active galactic nuclei (AGN). In this paradigm absorption is only witnessed in (close to)…

Obscured AGN represent a significant fraction of the entire AGN population, especially at high redshift (~70% at z=3--5). They are often characterized by the presence of large gas and dust reservoirs that are thought to sustain and possibly…

We present spectroscopic observations for 64 radio galaxies having ultra steep radio spectra. Twenty-nine objects have redshifts $z>2$, the largest redshifts being almost 4. Our ultra steep spectrum (USS) criterion ($\alpha < -1$) has…

Dark matter haloes in which galaxies reside are likely to have a significant impact on their evolution. We investigate the link between dark matter haloes and their constituent galaxies by measuring the angular two-point correlation…