Related papers: Active Galactic Nuclei

We present the discovery of a large gradual apparent fading event in optical and near-infrared wavelengths in a quasar at z=1.767 by a factor of 20-30 (in optical) over a period of ~20 years in the observed frame. This pronounced fading…

We measure long (2200-4000 ang) and short (1450-2200 ang) wavelength spectral slopes \alpha (F_\nu proportional to \nu^\alpha) for quasar spectra from the Sloan Digital Sky Survey. The long and short wavelength slopes are computed from 3646…

Active galactic nuclei (AGNs) are known to exhibit optical/UV variability and most of them can be well modeled by the damped random walks. Physical processes that are not related to the accretion disk, such as tidal disruption events (TDE)…

We combine data from the MGC, SDSS and UKIDSS LAS surveys to produce ugrizYJHK luminosity functions and densities from within a common, low redshift volume (z<0.1, ~71,000 h_1^-3 Mpc^3 for L* systems) with 100 per cent spectroscopic…

We present the construction of a deep multi-wavelength PSF-matched photometric catalog in the UDS field following the final UKIDSS UDS DR11 release. The catalog includes photometry in 24 filters, from the MegaCam-uS (0.38 microns) band to…

The recently-finished Edinburgh UVX quasar survey at B < 18 is used together with other complete samples to estimate the shape and evolution of the optical luminosity function in the redshift range 0.3 < z < 2.2. There is a significantly…

High-redshift quasars are important tracers of structure and evolution in the early universe. However, they are very rare and difficult to find when using color selection because of contamination from late-type dwarfs. High-redshift quasar…

Using the public data from the Herschel wide field surveys, we study the far-infrared properties of optical-selected quasars from the Sloan Digital Sky Survey. Within the common area of $\sim 172~deg^2$, we have identified the far-infrared…

Recently, Carnall et al. discovered two bright high redshift quasars using the combination of the VST ATLAS and WISE surveys. The technique involved using the 3-D colour plane i-z:z-W1:W1-W2 with the WISE W1 (3.4 micron) and W2 (4.5 micron)…

We present preliminary results of the quasar survey in Large Sky Area Multi- Object Fiber Spectroscopic Telescope (LAMOST) first data release (DR1), which includes pilot survey and the first year regular survey. There are 3921 quasars…

This is the second paper in a series aimed at finding high-redshift quasars from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this paper, we…

Motivated by the idea of using quasars as standardizable candles for cosmology, we examine the relation between X-ray (at 2 keV, $L_{\rm 2keV}$) and ultraviolet (at 2500 Angstrom, $L_{\rm 2500}$) monochromatic luminosities of quasars using…

We present a catalog of nearby (z $\leq$ 0.5) quasars with significant features of post-starburst stellar populations in their optical spectra, so-called post-starburst quasars, or PSQs. After carefully decomposing spectra from the Sloan…

We show that using mid-IR color selection to find active galactic nuclei (AGN) is as effective in dense stellar fields such as the Magellanic Clouds as it is in extragalactic fields with low stellar densities using comparisons between the…

We present a measurement of the two-point autocorrelation function of photometrically-selected, high-$z$ quasars over $\sim$ 100 deg$^2$ on the Sloan Digitial Sky Survey Stripe 82 field. Selection is performed using three machine-learning…

We report initial results from a large Gemini program to observe z>~5.7 quasars with GNIRS near-IR spectroscopy. Our sample includes 50 quasars with simultaneous ~0.85-2.5 micron spectra covering the rest-frame ultraviolet and major broad…

We investigate the relationship between quasars and close companion galaxies using photometry and spectroscopy from the large data set of the SDSS DR16 survey. From the SDSS-QSO catalog of quasars, we selected objects with 0.1 < z < 0.35…

We investigate colour selection techniques for high redshift galaxies in the UKIDSS Ultra Deep Survey Early Data Release (UDS EDR). Combined with very deep Subaru optical photometry, the depth (K_AB = 22.5) and area (0.62 deg^2) of the UDS…

This paper presents a comprehensive study of quasar photometric classification and redshift estimation using machine learning techniques. We cross-matched photometric data from the Dark Energy Survey Data Release 2 (DES DR2) with…

We present a near-infrared photometric search for unresolved substellar companions and debris disks around white dwarfs in the UKIRT Infrared Deep Sky Survey Large Area Survey. We cross-correlate the SDSS DR4 and McCook & Sion catalogues of…