From Thin to Thick: The Impact of X‐Ray Irradiation on Accretion Disks in Active Galactic Nuclei

AbstractPhotoionized outflows in active galactic nuclei (AGNs) are thought to influence their circumnuclear and host galactic environment. However, the distance of the outflow with respect to the black hole is poorly constrained, which limits our understanding of the kinetic power by the outflow. Therefore, the impact of AGN outflows on their host galaxies is uncertain. If the density of the outflow is known, its distance can be derived. Density measurement via variability studies and density sensitive lines have been used, albeit not very effective in the X-ray band. Good measurements are rather demanding or challenging for the current generation of (grating) spectrometers. The next generation of spectrometers will certainly provide data with better quality and large quantity, leading to tight constraints on the location and the kinetic power of AGN outflows. This contribution summarizes the state-of-the-art in this field.

Download Full-text

The Scaling of Solar Flare Hard X-ray Emission to Other Flaring Objects in the Universe

Symposium - International Astronomical Union ◽

10.1017/s0074180900162862 ◽

2000 ◽

Vol 195 ◽

pp. 133-134

Author(s):

P. C. H. Martens

Keyword(s):

Active Galactic Nuclei ◽

Accretion Disks ◽

Galactic Nuclei ◽

Physical Parameters ◽

X Ray ◽

Transport Code ◽

Type Particle ◽

Fokker Planck Equations ◽

The Universe ◽

Fokker Planck

Fletcher & Martens have successfully modeled solar hard X-ray sources observed at the top and footpoints of flaring magnetic loops with a Fokker-Planck type particle transport code. I show here that there are invariances in the Fokker-Planck equations that make these results applicable to environments with vastly different physical parameters, such as hard X-ray flares in accretion disks in active galactic nuclei, and in RS CVn and ALGOL type binaries.

Download Full-text

The impact of disturbed galaxy clusters on the kinematics of active galactic nuclei

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3154 ◽

2020 ◽

Vol 499 (3) ◽

pp. 3792-3805

Author(s):

Lawrence E Bilton ◽

Kevin A Pimbblet ◽

Yjan A Gordon

Keyword(s):

Active Galactic Nuclei ◽

Galaxy Clusters ◽

Velocity Dispersion ◽

Signal To Noise Ratio ◽

Galactic Nuclei ◽

Sloan Digital Sky Survey ◽

X Ray ◽

Cluster Galaxies ◽

Sky Survey ◽

The Impact

ABSTRACT We produce a kinematic analysis of AGN-hosting cluster galaxies from a sample of 33 galaxy clusters selected using the X-ray Clusters Database (BAX) and populated with galaxies from the Sloan Digital Sky Survey Data Release 8. The 33 galaxy clusters are delimited by their relative intensity of member galaxy substructuring as a proxy to core merging to derive two smaller sub-samples of 8 dynamically active (merging) and 25 dynamically relaxed (non-merging) states. The AGN were selected for each cluster sub-sample by employing the WHAN diagram to the strict criteria of log10([N ii]/Hα) ≥ −0.32 and EWHα ≥ 6 Å, providing pools of 70 mergings and 225 non-merging AGN sub-populations. By co-adding the clusters to their respective dynamical states to improve the signal-to-noise ratio of our AGN sub-populations we find that merging galaxy clusters on average host kinematically active AGN between 0–1.5r200 as r200 → 0, where their velocity dispersion profile (VDP) presents a significant deviation from the non-AGN sub-population VDP by ≳3σ. This result is indicative that the AGN-hosting cluster galaxies have recently coalesced on to a common potential. Further analysis of the composite distributions illustrates non-merging AGN-hosting sub-populations have, on average, already been accreted and predominantly lie within backsplash regions of the projected phase-space. This suggests merging cluster dynamical states hold relatively younger AGN sub-populations kinematically compared with those found in non-merging cluster dynamical states.

Download Full-text

The role of failed accretion disk winds in active galactic nuclei

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320002628 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 82-86 ◽

Cited By ~ 1

Author(s):

Margherita Giustini ◽

Daniel Proga

Keyword(s):

Active Galactic Nuclei ◽

Accretion Disks ◽

Galactic Nuclei ◽

Broad Line ◽

X Ray ◽

Broad Line Region ◽

Line Region ◽

Gravitational Pull ◽

Theoretical Evidence

AbstractBoth observational and theoretical evidence point at outflows originating from accretion disks as fundamental ingredients of active galactic nuclei (AGN). These outflows can have more than one component, for example an unbound supersonic wind and a failed wind (FW). The latter is a prediction of the simulations of radiation-driven disk outflows which show that the former is accompanied by an inner failed component, where the flow struggles to escape from the strong gravitational pull of the supermassive black hole. This FW component could provide a physical framework to interpret various phenomenological components of AGN. Here we briefly discuss a few of them: the broad line region, the X-ray obscurer, and the X-ray corona.

Download Full-text

Hot Accretion Disks and the High Energy Background

Symposium - International Astronomical Union ◽

10.1017/s0074180900039292 ◽

1983 ◽

Vol 104 ◽

pp. 345-346

Author(s):

M. Kafatos ◽

Jean A. Eilek

Keyword(s):

Active Galactic Nuclei ◽

Accretion Disks ◽

Spectral Range ◽

Gamma Rays ◽

Gamma Ray ◽

Galactic Nuclei ◽

Seyfert Galaxies ◽

High Energy ◽

X Rays ◽

X Ray

The origin of the high energy (X-ray and gamma-ray) background may be attributed to discrete sources, which are usually thought to be active galactic nuclei (AGN) (cf. Rothschild et al. 1982, Bignami et al. 1979). At X-rays a lot of information has been obtained with HEAO-1 in the spectral range 2–165 keV. At gamma-rays the background has been estimated from the Apollo 15 and 16 (Trombka et al. 1977) and SAS-2 (Bignami et al. 1979) observations. A summary of some of the observations (Rothschild et al. 1982) is shown in Figure 1. The contribution of AGN to the diffuse high energy background is uncertain at X-rays although it is generally estimated to be in the 20–30% range (Rothschild et al. 1982). At gamma-rays, in the range 1–150 MeV, AGN (specifically Seyfert galaxies) could account for all the emission.

Download Full-text

Soft X-rays of AGN: Emission from Accretion Disks?

International Astronomical Union Colloquium ◽

10.1017/s0252921100044092 ◽

1997 ◽

Vol 163 ◽

pp. 805-806

Author(s):

R. Staubert ◽

T. Dörrer ◽

C. Müller ◽

P. Friedrich ◽

H. Brunner

Keyword(s):

Active Galactic Nuclei ◽

Accretion Disks ◽

Galactic Nuclei ◽

High Energy ◽

X Rays ◽

X Ray ◽

Sky Survey ◽

High Energy Tail ◽

Low Energies ◽

Excess Component

Soft X-ray spectra of many Active Galactic Nuclei (AGN) show structure which suggests excess emission at low energies, mostly below 1 keV. This was confirmed by the ROSAT spectra (0.1–2.4 keV) AGN in our samples which generally have steeper power law spectra than the canonical index of 0.7. The soft excess component may be the high energy tail of the big blue bump which in turn may be due to the integrated emission from an accretion disk around the central black hole.We discuss results of our spectral analysis of two different samples of AGN: 1) QSO/Seyfert-I from the ROSAT All Sky Survey (RASS) and 2) radio-quiet QSO from ROSAT Pointed Observations. The ROSAT data are combined with UV Data from IUE and hard X-ray data from various hard X-ray missions.

Download Full-text

Line Emission from Accretion Disks in Active Galactic Nuclei

Symposium - International Astronomical Union ◽

10.1017/s0074180900140975 ◽

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”).

Download Full-text

Gamma-Rays from Active Galactic Nuclei

Highlights of Astronomy ◽

10.1017/s1539299600005517 ◽

1983 ◽

Vol 6 ◽

pp. 505-510

Author(s):

M. Kafatos

Keyword(s):

Active Galactic Nuclei ◽

Accretion Disks ◽

Gamma Ray ◽

Galactic Nuclei ◽

Thermal Processes ◽

Relativistic Electrons ◽

Massive Black Holes ◽

X Ray ◽

Electrons And Positrons ◽

Γ Rays

Gamma-ray observations from active galactic nuclei (AGN) are important in trying to understand the nature of their central sources. A handful of mechanisms can give rise to γ-rays either from nonthermal or from thermal processes. Hot accretion disks around massive black holes in the centers of AGN could provide the required thermal electrons, pions and relativistic electrons and positrons to explain both the X-ray and γ-ray emission.

Download Full-text