scholarly journals Erratum to ‘POLAMI: Polarimetric Monitoring of AGN at Millimetre Wavelengths – I. The programme, calibration, and calibrator data products’, ‘POLAMI: Polarimetric Monitoring of Active Galactic Nuclei at Millimetre Wavelengths – II. Widespread circular polarization’ and ‘POLAMI: Polarimetric Monitoring of Active Galactic Nuclei at Millimetre Wavelengths – III. Characterization of total flux density and polarization variability of relativistic jets’.

2018 ◽  
Vol 475 (4) ◽  
pp. 5108-5108
Keyword(s):  
Active Galactic Nuclei ◽  
Circular Polarization ◽  
Flux Density ◽  
Galactic Nuclei ◽  
Total Flux ◽  
Relativistic Jets ◽  
Data Products

A FRAMEWORK FOR INTERPRETING OBSERVED PHENOMENA ASSOCIATED WITH RELATIVISTIC OUTFLOWS IN AGN

2008 ◽  
Vol 17 (09) ◽  
pp. 1521-1530 ◽  
Author(s):  
D. C. GABUZDA
Keyword(s):  
Active Galactic Nuclei ◽  
Circular Polarization ◽  
Faraday Rotation ◽  
Surrounding Medium ◽  
Galactic Nuclei ◽  
High Energy ◽  
Electromagnetic Current ◽  
Relativistic Jets ◽  
Relativistic Shocks ◽  
Abundant Evidence

A growing number of jets in active galactic nuclei (AGN) show clear signs of helical magnetic (B) fields: Faraday-rotation gradients across the VLBI jets, extended regions of jet with orthogonal B fields, transverse polarization and total-intensity structures characteristic of helical fields, interknot polarization implying underlying orthogonal B fields, and a predominance of orthogonal B fields in the VLBI cores. In addition, a link has now been found between the circular polarization detected in AGN cores and the presence of helical jet B fields within these cores. This now abundant evidence compels us to take very seriously the idea that many, possibly all, AGN jets have helical B fields. As a whole, the recent observational results considered here suggest that we must look at AGN jets as fundamentally electromagnetic, current-carrying structures if we wish to fully understand their nature. This provides an overall framework for interpreting various observed phenomena associated with the relativistic jets of AGN, including high-energy phenomena. Superposed on the structure of the underlying helical B field may be the effects of relativistic shocks and interaction with the surrounding medium in some cases; these may dominate observed phenomena locally, while it is the "intrinsic" helical B field of the jet itself that determines the global observed characteristics of the jet.

scholarly journals Polarimetric Properties of Blazars Caught by the WEBT

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 42
Author(s):  
Claudia M. Raiteri ◽  
Massimo Villata
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Plasma Jets ◽  
Line Of Sight ◽  
Optical Behaviour ◽  
Relativistic Jets ◽  
Comprehensive Picture ◽  
Multi Wavelength ◽  
Extreme Variability ◽  
Continuous Range

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 relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called “blazars”. The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the γ-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies.

The GLEAM 4-Jy Sample: The brightest radio-sources in the southern sky

2019 ◽  
Vol 15 (S356) ◽  
pp. 375-375
Author(s):  
Sarah White
Keyword(s):  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Visual Inspection ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Relativistic Jets ◽  
The Galaxy ◽  
Murchison Widefield Array ◽  
Past Activity

AbstractLow-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few “radio-loud” galaxies for robust studies in terms of redshift-evolution and/or environment. Hence our use of new observations from the Murchison Widefield Array (the SKA-Low precursor), over the southern sky, to construct the GLEAM 4-Jy Sample (1,860 sources at S151MHz > 4 Jy). This sample is dominated by AGN and is 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S178MHz > 10 Jy) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way galaxies evolve, we first need to correctly identify the galaxy hosting the radio emission. This has now been completed for the GLEAM 4-Jy Sample – through repeated visual inspection and extensive checks against the literature – forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment.

Relativistic Jets in Active Galactic Nuclei

2014 ◽  
Author(s):  
Geoffrey Bicknell ◽  
Mohammad Nawaz ◽  
Alexander Wagner ◽  
Masayuki Umemura ◽  
Brian McNamara ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Relativistic Jets

scholarly journals Intrinsic physical conditions and structure of relativistic jets in active galactic nuclei

2015 ◽  
Vol 447 (3) ◽  
pp. 2726-2737 ◽  
Author(s):  
E. E. Nokhrina ◽  
V. S. Beskin ◽  
Y. Y. Kovalev ◽  
A. A. Zheltoukhov
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Relativistic Jets ◽  
Physical Conditions

scholarly journals High Resolution X-ray Spectroscopy of Active Galactic Nuclei

1990 ◽  
Vol 115 ◽  
pp. 262-273
Author(s):  
Julian H. Krolik
Keyword(s):  
High Resolution ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Light Sources ◽  
Clusters Of Galaxies ◽  
Relativistic Jets ◽  
Bl Lac Objects ◽  
X Ray ◽  
Interstellar Material ◽  
Scientific Value

AbstractHigh-resolution X-ray spectroscopy has the potential to reveal a number of interesting features of active galactic nuclei, primarily, though not exclusively, through the measurement of absorption lines. After a brief review of the principal problems of AGN research, selected potential high-resolution observations are discussed with a view toward assessing their scientific value and the degree of resolution they will require. Two classes of observations pertaining directly to AGNs are discussed: Fe Kα spectroscopy relevant to the dynamical and thermal character of the emission line zones; and measurement of resonance line absorption by highly-ionized species in BL Lac objects, which should tell us about entrainment of interstellar material by relativistic jets. A third class of potentially important observations uses AGNs as background light sources in order to directly measure the distance to clusters of galaxies.

Sign in / Sign up

Export Citation Format

Share Document