Related papers: Discovery of Hidden Blazars
We present new clues to the problem of the radio loudness dichotomy arising from an extensive search for intranight optical variability in seven sets of optically luminous radio-quiet quasars and (radio-loud) BL Lacertae objects, which are…
We present Reverberation Mapping results after monitoring a sample of 17 high-z, high-luminosity quasars for more than 10 years using photometric and spectroscopic capabilities. Continuum and line emission flux variability is observed in…
We have carried out multi-colour imaging of the fields of a statistically complete sample of low-frequency selected radio loud quasars at 0.6<z<1.1, in order to determine the characteristics of their environments. The largest radio sources…
Significant clustering around the rarest luminous quasars is a feature predicted by dark matter theory combined with number density matching arguments. However, this expectation is not reflected by observations of quasars residing in a…
We present a new sample of 35 quasars selected from the FIRST radio survey and the Deeprange I-band survey (Postman et al. 1998, 2002). A comparison with the FIRST Bright Quasar survey samples reveals that this I-band selected sample is…
Recently, it was suggested that large concentrations or groups of quasars may trace sites of enhanced matter density at medium and high redshifts analogous to how galaxy clusters trace them in nearby space. We have checked existing quasar…
We present a study of a sample of 223 radio-loud quasars (up to redshift $<$0.3) in order to investigate their spectral properties. Twenty-six of these radio-loud quasars are identified as Flat Spectrum Radio Quasars (FSRQs) and fifty-four…
We examine the consistency of the unified scheme of the powerful extragalactic radio sources with the 408 MHz BRL sample from the equatorial sky region, selected at the same flux-density level as the 3CRR sample. We find that, unlike in the…
The radio properties of 11 obscured `radio-intermediate' quasars at redshifts z>~2 have been investigated using the European Very-Long-Baseline-Interferometry Network (EVN) at 1.66 GHz. A sensitivity of ~25 micro Jy per 14x17 mas2 beam was…
We present a study of the low-frequency radio properties of broad absorption line quasars (BALQSOs) from the LOFAR Two-metre Sky-Survey Data Release 1 (LDR1). The value-added LDR1 catalogue contains Pan-STARRS counterparts, which we match…
We report the first systematic search for blazars among broad-absorption-line (BAL) quasars. This is based on our intranight optical monitoring of a well-defined sample of 10 candidates selected on the criteria of a flat spectrum and an…
Broad absorption lines (BALs) found in a significant fraction of quasar spectra identify high-velocity outflows that might be present in all quasars and could be a major factor in feedback to galaxy evolution. Understanding the nature of…
Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the…
The detection of high-redshift ($z>$3) blazars enables the study of the evolution of the most luminous relativistic jets over cosmic time. More importantly, high-redshift blazars tend to host massive black holes and can be used to constrain…
Being dominated by non-thermal (synchrotron and inverse Compton) emission from a relativistic jet, blazars offer important clues to the structure and radiative processes in extragalactic jets. Crucial information is provided by blazars'…
Although radio-quiet quasars (RQQs) constitute >90% of optically-identified quasar samples their radio properties are only poorly understood. In this paper we present the results of a multi-frequency VLA study of 27 low-redshift RQQs. We…
The unification model for powerful radio galaxies and radio-loud quasars postulates that these objects are intrinsically the same but viewed along different angles. Herschel Space Observatory data permit the assessment of that model in the…
For many years some astronomers have continued to argue, using redshift periodicities and quasar-galaxy associations, that quasars may be closer than their redshifts imply. Here, for the first time using raw radio data, I re-examine this…
The rareness of blazars, combined with the previous history of relatively shallow, single-band surveys, has dramatically colored our perception of these objects. Despite a quarter-century of research, it is not at all clear whether current…
Using the 2MASS Second Incremental Data Release, we have searched for near infrared counterparts to 13214 quasars from the Veron-Cetty & Veron(2000) catalog. We have detected counterparts within 4 arcsec for 2277 of the approximately 6320…