Related papers: What's Emitting the Broad Emission Lines?
Massive outflows are known to exist, in the form of extended emission-line regions (EELRs), around about one-third of powerful FR II radio sources. We investigate the origin of these EELRs by studying the emission-line regions around…
We studied the spectra of six $z \sim 2.2$ quasars obtained with the X-shooter spectrograph at the Very Large Telescope. The redshift of these sources and X-shooter's spectral coverage allow us to cover the rest spectral range $\sim1200 -…
What is the Broad Line Region (BLR) made of? What determines its location? Why is it sometimes missing? What controls its properties? Some recent results and new approaches which may shed light on these issues are briefly described.
We report the results from an ASCA observation of the high-luminosity, radio-loud quasar PKS 0637-752 (redshift 0.654), covering the 0.8-15 keV band in the quasar-frame. We find the source to have a luminosity ~10^46 erg/s in the 2-10 keV…
Recently, with the Chandra X-ray Telescope we have detected several local X-ray absorption lines along lines-of-sight towards distant quasars. These absorption lines are produced by warm/hot gas located in local intergalactic space and/or…
We report a serendipitous discovery of broad absorption lines that were newly formed in the spectrum of the high-redshift, luminous radio-loud quasar TEX 1726 + 344, in a time interval of only 12 years. This is the first quasar showing a…
The origin of the particles in the highest energy end of the cosmic ray spectrum is discussed in the context of the wider problem of the origin of the whole cosmic radiation as observed at the Earth. In particular we focus our attention on…
Gas outflows appear to be a phenomenon shared by the vast majority of quasars. Observations indicate that there is wide range in outflow prominence. In this paper we review how the 4D eigenvector 1 scheme helps to organize observed…
Theoretically, bound binaries of massive black holes are expected as the natural outcome of mergers of massive galaxies. From the observational side, however, massive black hole binaries remain elusive. Velocity shifts between narrow and…
The contributions of different radiation mechanisms to the diffuse gamma-ray emission of the galactic disk are studied in a broad energy region from X-rays to very high energy gamma rays.
A method is proposed for measuring the size of the broad emission line region (BLR) in quasars using broadband photometric data. A feasibility study, based on numerical simulations, points to the advantages and pitfalls associated with this…
Broad absorption line quasars are among the objects presenting the fastest outflows. The launching mechanism itself is not completely understood. Models in which they could be launched from the accretion disk, and then curved and…
A new model is presented which explains the origin of the broad emission lines observed in the LINER/Seyfert nucleus of M81 in terms of a steady state spherically symmetric inflow, amounting to 1 x 10^-5 Msun/yr, which is sufficient to…
Some considerations of long wavelength and broadband radiation sources based on the emission of the coherent radiation by a train of short relativistic electron bunches moving in an open resonator along an arc-like or undulator trajectories…
Quasars accreting matter at very high rates (known as extreme Population A [xA]) may provide a new class of distance indicators covering cosmic epochs from present day up to less than 1 Gyr from the Big Bang. We report on the developments…
We present a correlation between the presence of luminous extended emission-line regions (EELRs) and the metallicity of the broad-line regions (BLRs) of low-redshift quasars. The result is based on ground-based [O III] 5007 narrow-band…
We show that invaluable information on the structure of quasar outflows can be obtained by considering microlensing (ML) induced variability of absorption line troughs in lensed quasars. Depending on the structure and geometry of the…
Recent multifrequency observations contribute to derive a comprehensive picture of the origin and evolution of relativistic particles in galaxy clusters. In this review I briefly discuss theoretical aspects and open problems of this…
We present a brief description of a model for the broad emission line region (BELR) in quasars, which is supported by analysis of CIV and other emission lines in the spectra of high-z SDSS quasars. Specifically we consider a two-component…
Recent observational and theoretical results on blazars are presented and discussed. We are beginning to understand the rich phenomenology of blazars, and we are finding trends which will hopefully lead us to unveil the physics of these…