Active Galactic Nuclei in the Extreme Ultraviolet

EUV observations could provide valuable and unique information about the nature of active galactic nuclei. I discuss their potential usefulness and review some of the main results obtained so far with the ROSAT WFC and the EUVE instruments. About three dozen sources, mostly Seyfert galaxies and BL Lacertae objects, have already been identified, and spectroscopic measurements of several of them have yielded a number of surprises. However, more observations are clearly needed to confirm some of the reported spectral features and to validate their interpretation.

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Understanding the origin of radio outflows in Seyfert galaxies using radio polarimetry

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003014 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 247-251

Author(s):

Biny Sebastian ◽

Preeti Kharb ◽

Christopher P. O’ Dea ◽

Jack F. Gallimore ◽

Stefi A. Baum ◽

...

Keyword(s):

Magnetic Fields ◽

Radio Emission ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Seyfert Galaxy ◽

Seyfert Galaxies ◽

Starburst Galaxies ◽

Galactic Magnetic Fields ◽

5 Ghz

AbstractThe role of starburst winds versus active galactic nuclei (AGN) jets/winds in the formation of the kiloparsec scale radio emission seen in Seyferts is not yet well understood. In order to be able to disentangle the role of various components, we have observed a sample of Seyfert galaxies exhibiting kpc-scale radio emission suggesting outflows, along with a comparison sample of starburst galaxies, with the EVLA B-array in polarimetric mode at 1.4 GHz and 5 GHz. The Seyfert galaxy NGC 2639, shows highly polarized secondary radio lobes, not observed before, which are aligned perpendicular to the known pair of radio lobes. The additional pair of lobes represent an older epoch of emission. A multi-epoch multi-frequency study of the starburst-Seyfert composite galaxy NGC 3079, reveals that the jet together with the starburst superwind and the galactic magnetic fields might be responsible for the well-known 8-shaped radio lobes observed in this galaxy. We find that many of the Seyfert galaxies in our sample show bubble-shaped lobes, which are absent in the starburst galaxies that do not host an AGN.

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Chemical abundances in Seyfert galaxies – V. The discovery of shocked emission outside the AGN ionization axis

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa194 ◽

2020 ◽

Vol 501 (1) ◽

pp. L54-L59

Author(s):

R A Riffel ◽

O L Dors ◽

M Armah ◽

T Storchi-Bergmann ◽

A Feltre ◽

...

Keyword(s):

Electron Temperature ◽

Active Galactic Nuclei ◽

Direct Evidence ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Chemical Abundances ◽

Temperature Distributions ◽

Field Unit ◽

Dusty Torus ◽

Integral Field

ABSTRACT We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to $\gtrsim 30\, 000\,$K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle.

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Compton-Thick AGN in the NuSTAR ERA VII. A joint NuSTAR, Chandra, and XMM-Newton Analysis of Two Nearby, Heavily Obscured Sources

The Astrophysical Journal ◽

10.3847/1538-4357/ac1fee ◽

2021 ◽

Vol 922 (2) ◽

pp. 159

Author(s):

A. Traina ◽

S. Marchesi ◽

C. Vignali ◽

N. Torres-Albà ◽

M. Ajello ◽

...

Keyword(s):

Spectral Analysis ◽

Energy Range ◽

Active Galactic Nuclei ◽

Column Density ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Line Of Sight ◽

Broad Energy Range ◽

Larger Sample ◽

Broad Energy

Abstract We present the joint Chandra, XMM-Newton, and NuSTAR analysis of two nearby Seyfert galaxies, NGC 3081 and ESO 565-G019. These are the only two having Chandra data in a larger sample of 10 low-redshift (z ≤ 0.05), candidates Compton-thick (CT) Active Galactic Nuclei selected in the 15–150 keV band with Swift-BAT that were still lacking NuSTAR data. Our spectral analysis, performed using physically motivated models, provides an estimate of both the line-of-sight (l.o.s.) and average (N H,S ) column densities of the two torii. NGC 3081 has a Compton-thin l.o.s. column density N H,z = [0.58–0.62] × 1024 cm−2, but the N H,S , beyond the CT threshold (N H,S = [1.41–1.78] × 1024 cm−2), suggests a “patchy” scenario for the distribution of the circumnuclear matter. ESO 565-G019 has both CT l.o.s. and N H,S column densities (N H,z > 2.31 × 1024 cm−2 and N H,S > 2.57 × 1024 cm−2, respectively). The use of physically motivated models, coupled with the broad energy range covered by the data (0.6–70 keV and 0.6–40 keV, for NGC 3081 and ESO 565-G019, respectively) allows us to constrain the covering factor of the obscuring material, which is C TOR = [0.63–0.82] for NGC 3081, and C TOR = [0.39–0.65] for ESO 565-G019.

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Spectral Variability in Seyfert Galaxies

Symposium - International Astronomical Union ◽

10.1017/s007418090015507x ◽

1987 ◽

Vol 121 ◽

pp. 161-167

Author(s):

B.M. Peterson

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Broad Line ◽

Spectral Variability ◽

Broad Line Region ◽

Broad Emission ◽

Line Region ◽

Order Of Magnitude ◽

Optical Continuum

Recent observations of spectral variability in active galactic nuclei have established the connection between the broad emission-line and optical continuum flux changes. The inferred size of the broad-line region is at least an order of magnitude smaller than conventional estimates based on photoionization models, which leads to new conclusions about the nature of the broad-line region.

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Study of the Galactic Center with a High Resolution Gamma Ray Telescope

Symposium - International Astronomical Union ◽

10.1017/s0074180900187145 ◽

1989 ◽

Vol 136 ◽

pp. 639-643

Author(s):

Ervin J. Fenyves ◽

Stephen N. Balog ◽

David B. Cline ◽

M. Atac

Keyword(s):

Black Holes ◽

Active Galactic Nuclei ◽

Gamma Ray ◽

Galactic Center ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

Hole Formation ◽

Massive Black Holes ◽

General Outcome ◽

Enormous Amount

It is generally accepted that massive black holes are the most likely source for the energy radiated from active galactic nuclei, and may explain the enormous amount of energy emitted by quasars, radio galaxies, Seyfert galaxies, and BL Lacertid objects. Although the detailed mechanisms of the black hole formation in galactic nuclei are not clear at present, it seems to be quite possible that the formation of massive black holes is a general outcome of the evolution of galactic nuclei.

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The Compact Magnetic Field Structures of AGN from Space VLBI Polarization Observations

Symposium - International Astronomical Union ◽

10.1017/s007418090022072x ◽

2001 ◽

Vol 205 ◽

pp. 134-135

Author(s):

D.C. Gabuzda ◽

J.L. Gómez

Keyword(s):

Magnetic Field ◽

Active Galactic Nuclei ◽

Linear Polarization ◽

Line Emission ◽

Galactic Nuclei ◽

Emission Mechanism ◽

Bl Lac Objects ◽

Bl Lacertae ◽

Bl Lac ◽

Optical Line

BL Lacertae objects are active galactic nuclei with weak, sometimes undetectable, optical line emission and strong variability in total intensity and linear polarization over a broad range of wavelengths from ultraviolet to radio. It is believed that synchrotron radiation is the dominant emission mechanism virtually throughout the spectrum. Their strong linear polarization makes BL Lac objects prime targets for space VLBI polarization observations.

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