We show that the observational data of extragalactic radio sources tend to support the theoretical relationship between the jet precession period and the optical luminosity of the sources, as predicted by the model in which an accretion disk causes the central black hole to precess. Subject headings: accretion, accretion disks — black hole physics — galaxies: active — galaxies: jets

We report the discovery of a new gravitationally lensed radio source. Radio maps of MG 0751+2716 show four lensed images, which, at higher resolution, are resolved into long arcs of emission. A group of galaxies is present in optical images, including the principal lensing galaxy, with a much brighter galaxy just a few arcseconds away. We have measured the redshift of this brighter galaxy. No o...

We derive an X-ray luminosity function for active galactic nuclei (AGN) that accounts for the X-ray source counts in the 0.5–2.0 and 2–10 keV energy ranges, the redshift distribution of AGNs in the ROSAT Deep Survey (RDS), as well as the X-ray background (XRB) from 1–10 keV. We emphasize the role of X-ray absorption, which has a large effect on the faint end of the 2– 10 keV source counts, as w...

VLBI observations of relativistic outflows (jets) in galactic nuclei, complemented with detailed studies made in other spectral domains, have become an effective tool for investigating the physics of nuclear regions in galaxies. High-resolution radio observations access directly the regions where the jets are formed, and trace their evolution and interaction with the nuclear environment. The em...

I briefly mention a few possible applications of very high spectral resolution spectroscopy with CRIRES to the study of nearby galaxies. This includes the fields of AGN, dynamically cold systems, super stellar and emission line clusters, and a more speculative program on the measurement of gravitational redshifts.

Feedback from quasars and AGNs is being invoked frequently in several cosmological settings. Currently, order of magnitude, or more, uncertainties in the structure of both the wind and the ’obscuring torus’ make predictions highly uncertain. To make testable models of this ’cosmological feedback’ it is essential to understand the detailed structure of AGNs sufficiently well to predict their pro...

I discuss the possibility of production of high energy cosmic neutrinos (E ≥ 10 GeV) in cores of active galactic nuclei and study some of the effects of neutrino mixing on their subsequent propagation. I also discuss the prospects for observations of these high energy cosmic neutrinos in new km surface area underwater/ice neutrino telescopes.

We review the basic observed and inferred properties of the broad emission-line region in AGNs, as well as the basics of the reverberation-mapping technique that can be used to determine the size and structure of the region. We argue that the current best evidence points to a multi-component line-emitting region, with a disk-like structure, possibly an extension of the accretion disk itself, an...

MAGIC currently is the largest imaging atmospheric Cerenkov telescope world-wide. Since 2004, γ-ray emission from several active galactic nuclei in the GeV/TeV energy range has been detected, some of which were newly discovered as very-high energy γ-ray sources. The γ-rays are assumed to originate from particle acceleration processes in the AGN jets. We give an overview of the AGN observed and ...