相关论文: Modelling type 1 quasar colours in the era of Rubi…

Studies of the most luminous quasars at high redshift directly probe the evolution of the most massive black holes in the early Universe and their connection to massive galaxy formation. However, extremely luminous quasars at high redshift…

Quasars are variable on timescales from days to years in UV/optical, and generally appear bluer while they brighten. The physics behind the variations in fluxes and colors remains unclear. Using SDSS g and r band photometric monitoring data…

We present a method for studying the proximity effect and the density structure around redshift z=2-3 quasars. It is based on the probability distribution of Lyman-alpha pixel optical depths and its evolution with redshift. We validate the…

Bright quasar samples at high redshift are useful for investigating active galactic nuclei evolution. In this study, we describe XQz5, a sample of 83 ultraluminous quasars in the redshift range $4.5 < z < 5.3$ with optical and near-infrared…

We apply instance-based machine learning in the form of a k-nearest neighbor algorithm to the task of estimating photometric redshifts for 55,746 objects spectroscopically classified as quasars in the Fifth Data Release of the Sloan Digital…

The well-known anti-correlation between the optical/ultraviolet (UV) emission line equivalent widths of active galactic nuclei and the continuum luminosity (the so-called Baldwin effect) is a long-standing puzzle. One common hypothesis is…

We test the periodicity of quasar redshifts in the 2dF and SDSS surveys. In the overall surveys redshift peaks are already apparent in the brighter quasars. But by analyzing sample areas in detail it is shown that the redshifts fit very…

We model the optical to far-infrared SEDs of a sample of six type-1 and six type-2 quasars selected in the mid-infrared. The objects in our sample are matched in mid-IR luminosity and selected based on their Spitzer IRAC colors. We obtained…

A key goal of the Stage IV dark energy experiments Euclid, LSST and WFIRST is to measure the growth of structure with cosmic time from weak lensing analysis over large regions of the sky. Weak lensing cosmology will be challenging: in…

We use photometric data, from the optical to the mm for a large sample of optically selected radio-quiet quasars, at low and high redshifts, to test emission models from circum-nuclear dusty torii around them. Model parameters, such as dust…

We report the results of near-infrared spectroscopic observations of 37 quasars in the redshift range $6.3< z\le7.64$, including 32 quasars at $z>6.5$, forming the largest quasar near-infrared spectral sample at this redshift. The spectra,…

The addition of deep near infrared images to the database provided by the HDF-S WFPC2 is essential to monitor the SEDs of the objects on a wide baseline and address a number of key issues including the total stellar content of baryonic…

We have conducted ultra-deep optical and deep near-infrared observations of a field around the z=1.226 radio-quiet quasar 104420.8+055739 from the Clowes-Campusano LQG of 18 quasars at z~1.3 in search of associated galaxy clustering.…

We have made radio observations of 87 optically selected quasars at 5 GHz with the VLA in order to measure the radio power for these objects and hence determine how the fraction of radio-loud quasars varies with redshift and optical…

Our group has developed a technique that makes use of the observed non-linear relation between the ultraviolet and the X-ray luminosity in quasars to provide an independent measurement of their distances, thus turning quasars into…

We present a detailed analysis of our ability to determine stellar masses, ages, reddening and extinction values, and star formation rates of high-redshift galaxies by modeling broad-band SEDs with stellar population synthesis. In order to…

The observed optical colors of quasars are generally interpreted in one of two frameworks: unified models which attribute color to random orientation of the accretion disk along the line-of-sight, and evolutionary models which invoke…

We present Keck high-quality rest-frame ultraviolet (UV) through optical spectra of 21 Type Ia supernovae (SNe Ia) in the redshift range 0.11 < z < 0.37 and a mean redshift of 0.22 that were discovered during the Sloan Digital Sky Survey-II…

Using a large sample of quasar spectra from the SDSS, we examine the composite spectral trends of quasars as functions of both redshift and luminosity, independently of one another. Aside from the well known Baldwin effect (BE) -- the…

Strongly lensed quasars with time-delay measurements are well known to provide the "time-delay distances" $D_{\Delta t}=(1+z_L)D_LD_S/D_{LS}$ and the angular diameter distances to lens galaxies $D_L$. These two kinds of distances give…