scholarly journals ROSAT Studies of Extragalactic Radio Sources

1996 ◽  
Vol 175 ◽  
pp. 259-262 ◽  
Author(s):  
W. Brinkmann ◽  
J. Siebert ◽  
W. Yuan
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Optical Data ◽  
Radio Sources ◽  
Complementary Information ◽  
X Ray ◽  
Physical Conditions ◽  
Γ Ray

Complementary information over a large energy range appears to be the best way to study the class properties of Active Galactic Nuclei (AGN). While radio data provide superior spatial resolution required for the analysis of source structures and their morphology, optical data are a necessary ingredient for the classification of the objects and for the determination of their redshifts. Finally, X-ray (and more recently γ-ray) observations give vital information about the energetics of the central engines and on the physical conditions of the ‘heart of the machine’.

scholarly journals Fine Classification of QSOs and Seyferts for Activity Types Based on SDSS Spectroscopy

2021 ◽  
Vol 7 ◽  
Author(s):  
A. M. Mickaelian ◽  
H. V. Abrahamyan ◽  
G. M. Paronyan ◽  
G. A. Mikayelyan
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Spectral Classification ◽  
X Ray ◽  
Activity Types ◽  
Larger Sample ◽  
Variable Radio ◽  
Fine Classification

Using the SDSS spectroscopy, we have carried out fine optical spectral classification for activity types for 710 AGN candidates. These objects come from a larger sample of some 2,500 candidate AGN using pre-selection by various samples; bright objects of the Catalog of Quasars and Active Galactic Nuclei, AGN candidates among X-ray sources, optically variable radio sources, IRAS extragalactic objects, etc. A number of papers have been published with the results of this spectral classification. More than 800 QSOs have been identified and classified, including 710 QSOs, Seyferts and Composites. The fine classification shows that many QSOs show the same features as Seyferts, i.e., subtypes between S1 and S2 (S1.2, S1.5, S1.8 and S1.9). We have introduced subtypes for the QSOs: QSO1.2, QSO1.5, QSO1.8, QSO1.9, though the last subtype does not appear in SDSS wavelength range due to mostly highly redshifted Hα (the main line for identification of the 1.9 subtype). Thus, independent of the luminosity (which serves as a separator between QSOs and Seyferts), AGN show the same features. We also have classified many objects as Composites, spectra having composite characteristics between Sy and LINERs, Sy and HII or LINERs and HII; in some cases all three characteristics appear together resulting as Sy/LINER/HII subtype. The QSOs subtypes together with Seyfert ones allow to follow AGN properties along larger redshift range expanding our knowledge on the evolution of AGN to more distant Universe represented by QSOs.

scholarly journals Steps toward Determination of the Size and Structure of the Broad‐Line Region in Active Galactic Nuclei. X. Variability of Fairall 9 from Optical Data

1997 ◽  
Vol 112 (2) ◽  
pp. 271-283 ◽  
Author(s):  
M. Santos‐Lleo ◽  
E. Chatzichristou ◽  
C. Mendes de Oliveira ◽  
C. Winge ◽  
D. Alloin ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Optical Data ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region ◽  
Size And Structure

scholarly journals Examining the physical conditions of a warm corona in active galactic nuclei accretion discs

2019 ◽  
Vol 491 (3) ◽  
pp. 3553-3561 ◽  
Author(s):  
D R Ballantyne
Keyword(s):  
Active Galactic Nuclei ◽  
Power Law ◽  
Galactic Nuclei ◽  
Accretion Discs ◽  
Internal Heating ◽  
One Dimensional ◽  
X Ray ◽  
Physical Conditions ◽  
Gas Layer ◽  
Hot Corona

ABSTRACT A warm corona at the surface of an accretion disc has been proposed as a potential location for producing the soft excess commonly observed in the X-ray spectra of active galactic nuclei (AGNs). In order to fit the observed data, the gas must be at temperatures of ∼1 keV and have an optical depth of τT ≈ 10–20. We present one-dimensional calculations of the physical conditions and emitted spectra of a τT = 10 or 20 gas layer subject to illumination from an X-ray power law (from above), a blackbody (from below), and a variable amount of internal heating. The models show that a warm corona with kT ∼ 1 keV can develop, producing a strong Comptonized soft excess, but only if the internal heating flux is within a relatively narrow range. Similarly, if the gas density of the layer is too large then efficient cooling will stop a warm corona from forming. The radiation from the hard X-ray power law is crucial in producing a warm corona, indicating that a warm and hot corona may coexist in AGN accretion discs, and their combined effect leads to the observed soft excess. Intense heating of a warm corona leads to steep X-ray spectra with ionized Fe K α lines, similar to those seen in some narrow-line Seyfert 1 galaxies.

scholarly journals The XXL Survey

2018 ◽  
Vol 620 ◽  
pp. A6 ◽  
Author(s):  
O. Melnyk ◽  
A. Elyiv ◽  
V. Smolčić ◽  
M. Plionis ◽  
E. Koulouridis ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galaxy Clusters ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Small Scale ◽  
Radio Sources ◽  
Large Area ◽  
Distance Method ◽  
X Ray ◽  
Structure Information

Context. This work is part of a series of studies focusing on the environment and the properties of the X-ray selected active galactic nuclei (AGN) population from the XXL survey. The present survey, given its large area, continuity, extensive multiwavelength coverage, and large-scale structure information, is ideal for this kind of study. Here, we focus on the XXL-South (XXL-S) field. Aims. Our main aim is to study the environment of the various types of X-ray selected AGN and investigate its possible role in AGN triggering and evolution. Methods. We studied the large-scale (>1 Mpc) environment up to redshift z = 1 using the nearest neighbour distance method to compare various pairs of AGN types. We also investigated the small-scale environment (<0.4 Mpc) by calculating the local overdensities of optical galaxies. In addition, we built a catalogue of AGN concentrations with two or more members using the hierarchical clustering method and we correlated them with the X-ray galaxy clusters detected in the XXL survey. Results. It is found that radio detected X-ray sources are more obscured than non-radio ones, though not all radio sources are obscured AGN. We did not find any significant differences in the large-scale clustering between luminous and faint X-ray AGN, or between obscured and unobscured ones, or between radio and non-radio sources. At local scales (<0.4 Mpc), AGN typically reside in overdense regions, compared to non-AGN; however, no differences were found between the various types of AGN. A majority of AGN concentrations with two or more members are found in the neighbourhood of X-ray galaxy clusters within <25–45 Mpc. Our results suggest that X-ray AGN are typically located in supercluster filaments, but they are also found in over- and underdense regions.

scholarly journals Line Emission from Accretion Disks in Active Galactic Nuclei

1989 ◽  
Vol 134 ◽  
pp. 255-256
Author(s):  
S. Collin-Souffrin ◽  
A.M. Dumont
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disks ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
X Rays ◽  
X Ray ◽  
Outer Disk ◽  
Inverse Compton ◽  
Inner Region

If accretion disks are present in AGN and extend to large radii they should contribute substantially to the Broad Line emission. The outer regions of the disk are indeed illuminated by a small amount of ionizing radiation. X-rays are emitted by the central inner region near the black hole, and they are either received directly by the outer disk, owing to its “flaring” shape (Cunningham, 1976), or partly reflected towards the disk by a hot Compton thin medium (Begelmann and McKee, 1983). X-ray photons are also produced through the Inverse Compton mechanism in compact radio sources located above the disk(“jet model”).

scholarly journals Swift monitoring and Suzaku spectroscopy of the γ-ray detected narrow-line Seyfert 1 galaxy 1H 0323+342

2014 ◽  
Vol 10 (S312) ◽  
pp. 66-67
Author(s):  
S. Yao ◽  
W. Yuan ◽  
S. Komossa ◽  
D. Grupe ◽  
L. Fuhrmann ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Broad Band ◽  
Galactic Nuclei ◽  
Optical Monitoring ◽  
Narrow Line ◽  
Black Hole Mass ◽  
X Ray ◽  
Small Black Hole ◽  
Special Subset ◽  
Γ Ray

Abstract1H 0323+342 is one of the rare γ-ray detected narrow-line Seyfert 1 galaxies (NLS1s), a special subset of active galactic nuclei (AGN) owing to their hybrid behavior of both NLS1s and blazars. The rarity of such kind of sources makes their properties far from being understood. We analyze simultaneous X-ray and UV/optical monitoring observations of 1H 0323+342 performed by Swift over ~7 years. The UV/X-ray correlation and the broad band SED reveal that the X-ray band is dominated by the disk/corona emission during the observations. The large normalized excess variance of the X-ray variability detected with Suzaku suggests a relatively small black hole mass of the order of 107M⊙, consistent with the estimation based on the broad Hβ line in the optical band.

scholarly journals Kiloparsec-scale jet-driven feedback in AGN probed by highly ionized gas: A MUSE/VLT perspective

2019 ◽  
Vol 15 (S359) ◽  
pp. 221-225
Author(s):  
A. Rodríguez-Ardila ◽  
M. A. Fonseca-Faria
Keyword(s):  
Low Power ◽  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Field Of View ◽  
Coronal Line ◽  
Ionized Gas ◽  
X Ray ◽  
Physical Conditions ◽  
Radio Jets

AbstractWe employ optical spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) combined with X-ray and radio data to study the highly-ionized gas (HIG) phase of the feedback in a sample of five local nearby Active Galactic Nuclei (AGN). Thanks to the superb field of view and sensitivity of MUSE, we found that the HIG, traced by the coronal line [Fe vii] λ6089, extends to scales not seen before, from 700 pc in Circinus and up to ∼2 kpc in NGC 5728 and NGC 3393. The gas morphology is complex, following closely the radio jet and the X-ray emission. Emission line ratios suggest gas excitation by shocks produced by the passage of the radio jet. This scenario is further supported by the physical conditions derived for the HIG, stressing the importance of the mechanical feedback in AGN with low-power radio jets.

scholarly journals Physical Conditions in Active Galactic Nuclei

1989 ◽  
Vol 134 ◽  
pp. 535-536
Author(s):  
V. S. Artyukh
Keyword(s):  
Magnetic Field ◽  
Synchrotron Radiation ◽  
Active Galactic Nuclei ◽  
Relativistic Electron ◽  
Angular Resolution ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Electron Number ◽  
Physical Conditions

Self-absorption of synchrotron radiation in compact radio sources gives rise to a low-frequency cutoff in their spectra. To study this effect it is necessary to observe the radio sources at meter wavelengths with angular resolution < 1″. Such observations of compact radio sources located in active galactic nuclei lead to estimates of magnetic field strengths and relativistic electron number densities in the AGNs.

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