1,220 datasets found

Propagation of the radio waves from distant compact radio sources through turbulent interstellar plasma in our Galaxy leads to twinkling of these sources, a phenomenon called...

Strong gravitational lensing distorts our view of sources at cosmological distances but brings invaluable constraints on the mass content of foreground objects and on the...

Detailed studies of relativistic jets in active galactic nuclei (AGN) require high-fidelity imaging at the highest possible resolution. This can be achieved using very long...

We select a sample of 90 obscured (type 2) AGN with 1.45<z<3.05 from the zCOSMOS-deep galaxy sample by 5 sigma-detection of the high-ionization CIV {lambda}1549 narrow...

The advent of the Fermi gamma-ray space telescope with its superb sensitivity, energy range, and unprecedented capability to monitor the entire 4{pi} sky within less than 2-3 h,...

Quasi-stellar object (QSO) spectral templates are important both to QSO physics and for investigations that use QSOs as probes of intervening gas and dust. However, combinations...

A tiny fraction of the quasar population shows remarkably weak emission lines. Several hypotheses have been developed, but the weak line quasar (WLQ) phenomenon still remains...

Although the variability in the ultraviolet and optical domain is one of the major characteristics of quasars, the dominant underlying mechanisms are still poorly understood....

The number and spatial distribution of confirmed quasi-stellar objects (QSOs) behind the Magellanic system is limited. This undermines their use as astrometric reference objects...

We present a new catalogue of blazars based on multifrequency surveys and on an extensive review of the literature. Blazars are classified as BL Lacertae objects, as flat...

The very large and increasing number of quasars reckoned from various sky surveys leads to a large quantity of data which brings various and inhomogeneous information in the...

Although Blazars are a small fraction of the overall AGN population they are expected to be the dominant population of extragalactic sources in the hard X-ray and gamma-ray...

We present Chandra and Spitzer data for the 186, extragalactic, hard 2-10keV X-ray selected sources, which lie in the central part of the Chandra Deep Field South (CDFS). For...

We present the broad band, radio - to - X-ray, properties of a large sample of mostly previously optically unidentified radio-loud X-ray sources from the correlation of a ROSAT...

LBQS 0302-0019 is a blue quasar (QSO) at z~3.3 that hosts powerful outflows and resides in a complex environment consisting of an obscured active galactic nucleus (AGN)...

We explore the extinction/reddening of ~35000 uniformly selected quasars with 0<z{<=}5.3 in order to better understand their intrinsic optical/ultraviolet (UV) spectral...

This is the third 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...

Using the 2MASS Second Incremental Data Release (Cat. ), we have searched for near-infrared counterparts to 13214 quasars from the Veron-Cetty & Veron (Cat. ) catalog. We...

We present a new sample of quarter-Jansky flat-spectrum radio sources selected to search for high-redshift quasars and to study the evolution of the flat-spectrum quasar...

We present a systematic study of weak intervening CaII absorbers at low redshift (z<0.5), based on the analysis of archival high-resolution (R>=45000) optical spectra of...