scholarly journals 3.28. Three-dimensional distribution of the nuclear mirrors in NGC 1068

1998 ◽  
Vol 184 ◽  
pp. 145-146
Author(s):  
Makoto Kishimoto
Keyword(s):  
Active Galactic Nuclei ◽  
Three Dimensional ◽  
Galactic Nuclei ◽  
Unified Model ◽  
Uv Imaging ◽  
Dimensional Distribution ◽  
Imaging Polarimetry ◽  
Ngc 1068

Recently, the HST imaging observations have revealed that the central arc second region in NGC 1068 has a clumpy structure (Macchetto et al., 1994) and the HST UV imaging polarimetry has revealed the centrosymmetric pattern of the position angles of polarization (Capetti et al., 1995), which indicates that the medium in this region is actually scattering the radiation from a small source, in accordance with the unified model of active galactic nuclei (Antonucci & Miller, 1985).

scholarly journals HST Observations of Active Galactic Nuclei

1999 ◽  
Vol 194 ◽  
pp. 12-24
Author(s):  
F. Duccio Macchetto
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Unified Model ◽  
Ngc 1068 ◽  
Major Progress

The HST has made many contributions to all areas of research in the field of AGN, and I have selected three topics where major progress in our understanding has been made over the last two years. The study of the NLR is key to understanding to what extent the unified model for AGN is applicable. In particular, understanding how the NLR is ionized and how its morphology is defined makes an important contribution to clarify the differences between Seyfert 1 and Seyfert 2. Work by Macchetto et al., Capetti et al., Axon et al., and Wilson et al. has helped clarify the picture. Our work on NGC 1068, Mrk 3, Mrk 7, Mrk 348, Mrk 6, and Mrk 573 has shown the following important properties: a) all AGN with a linear radio jet show emission-line morphology ([O III], [O II], Hα) which is aligned along the jet in a surrounding cocoon; b) those AGN with radio lobes show emission-line morphology which is filamentary and coincident with the position of the lobes; and c) in NGC 1068 and in Mrk 3 we have measured transverse velocities to the radio-jet as large as 1700 km s−1. These velocities measured at different positions across the radio-jet show an almost perfect velocity ellipsoid, indicating that the cocoon around the jet is expanding, compresses the ISM and shocks and ionizes the region.

scholarly journals Gamma-Ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 36
Author(s):  
Yoshiyuki Inoue ◽  
Dmitry Khangulyan ◽  
Akihiro Doi
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Thermal Activity ◽  
X Ray ◽  
Cascade Models ◽  
Coronal Activity ◽  
Ngc 1068 ◽  
High Energy Particles

To explain the X-ray spectra of active galactic nuclei (AGN), non-thermal activity in AGN coronae such as pair cascade models has been extensively discussed in the past literature. Although X-ray and gamma-ray observations in the 1990s disfavored such pair cascade models, recent millimeter-wave observations of nearby Seyferts have established the existence of weak non-thermal coronal activity. In addition, the IceCube collaboration reported NGC 1068, a nearby Seyfert, as the hottest spot in their 10 yr survey. These pieces of evidence are enough to investigate the non-thermal perspective of AGN coronae in depth again. This article summarizes our current observational understanding of AGN coronae and describes how AGN coronae generate high-energy particles. We also provide ways to test the AGN corona model with radio, X-ray, MeV gamma ray, and high-energy neutrino observations.

scholarly journals Exploring the inner parsecs of active galactic nuclei using near-infrared high resolution polarimetric simulations with MontAGN

2018 ◽  
Vol 612 ◽  
pp. A69 ◽  
Author(s):  
L. Grosset ◽  
D. Rouan ◽  
D. Gratadour ◽  
D. Pelat ◽  
J. Orkisz ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Optical Depth ◽  
Near Infrared ◽  
Galactic Nuclei ◽  
Constant Density ◽  
Characteristic Model ◽  
Infrared Observations ◽  
Current Estimation ◽  
Direct Light ◽  
Ngc 1068

Aims. In this paper we aim to constrain the properties of dust structures in the central first parsecs of active galactic nuclei (AGN). Our goal is to study the required optical depth and composition of different dusty and ionised structures. Methods. We developed a radiative transfer code called Monte Carlo for Active Galactic Nuclei (MontAGN), which is optimised for polarimetric observations in the infrared. With both this code and STOKES, designed to be relevant from the hard X-ray band to near-infrared wavelengths, we investigate the polarisation emerging from a characteristic model of the AGN environment. For this purpose, we compare predictions of our models with previous infrared observations of NGC 1068, and try to reproduce several key polarisation patterns revealed by polarisation mapping. Results. We constrain the required dust structures and their densities. More precisely, we find that the electron density inside the ionisation cone is about 2.0 × 109 m−3. With structures constituted of spherical grains of constant density, we also highlight that the torus should be thicker than 20 in term of K-band optical depth to block direct light from the centre. It should also have a stratification in density: a less dense outer rim with an optical depth at 2.2 μm typically between 0.8 and 4 for observing the double scattering effect previously proposed. Conclusions. We bring constraints on the dust structures in the inner parsecs of an AGN model supposed to describe NGC 1068. When compared to observations, this leads to an optical depth of at least 20 in the Ks band for the torus of NGC 1068, corresponding to τV ≈ 170, which is within the range of current estimation based on observations. In the future, we will improve our study by including non-uniform dust structures and aligned elongated grains to constrain other possible interpretations of the observations.

Imaging Polarimetry of Eta Carinae with the Hubble Space Telescope

1999 ◽  
Vol 169 ◽  
pp. 255-259
Author(s):  
Regina E. Schulte-Ladbeck ◽  
Anna Pasquali ◽  
Mark Clampin ◽  
Antonella Nota ◽  
John Hillier ◽  
...  
Keyword(s):  
Hubble Space Telescope ◽  
Three Dimensional ◽  
Position Angle ◽  
Small Scale ◽  
Eta Carinae ◽  
V Band ◽  
Dimensional Distribution ◽  
Imaging Polarimetry ◽  
Insight Into ◽  
Size Scales

AbstractWe have taken advantage of the high spatial resolution attainable with the HST to map the linear polarization in the V band across the nebulosity surrounding Eta Car. There are several new results related to polarization variations on different size scales. First, we present a two-dimensional map of the amount and position angle of the polarization across the Homunculus. Second, we provide measurements of the polarization within prominent features such as the “jet”, the “paddle”, the “skirt”, and the “spot” in the south-eastern lobe. Third, we comment on polarization variations associated with the small-scale structure that can be seen in HST images (and which gives the lobes their cauliflower-like appearance). The new data provide insight into the three-dimensional distribution of dust about Eta Car.

scholarly journals Radiation pressure confinement – V. The predicted free–free absorption and emission in active galactic nuclei

2021 ◽  
Vol 508 (1) ◽  
pp. 680-697
Author(s):  
Alexei Baskin ◽  
Ari Laor
Keyword(s):  
Active Galactic Nuclei ◽  
Radiation Pressure ◽  
Galactic Nuclei ◽  
Radio Continuum ◽  
Absorption Frequency ◽  
Absorption And Emission ◽  
Scale Free ◽  
Spatially Resolved ◽  
Ngc 1068 ◽  
5 Ghz

ABSTRACT The effect of radiation pressure compression (RPC) on ionized gas in active galactic nuclei (AGNs) likely sets the photoionized gas density structure. The photoionized gas free–free absorption and emission are therefore uniquely set by the incident ionizing flux. We use the photoionization code cloudy RPC model results to derive the expected relations between the free–free emission and absorption properties and the distance from the AGN centre, for a given AGN luminosity. The free–free absorption frequency of RPC gas is predicted to increase from ∼100 MHz on the kpc scale to ∼100 GHz on the sub-pc scale, consistent with observations of spatially resolved free–free absorption. The free–free emission at 5 GHz is predicted to yield a radio loudness (R) of ∼0.03, below the typical observed values of R ∼ 0.1–1 in radio-quiet AGNs. However, the flat free–free radio continuum may become dominant above 100 GHz. The suggested detection of optically thin free–free emission in NGC 1068, on the sub-pc torus scale, is excluded as the brightness temperature is too high for optically thin free–free emission. However, excess emission observed with Atacama Large Millimeter/submillimeter Array (ALMA) above 150 GHz in NGC 1068 is consistent with the predicted free–free emission from gas just outside the broad-line region, a region that overlaps the hot dust disc resolved with GRAVITY. Extended ∼100 pc-scale free–free emission is also likely present in NGC 1068. Future sub-mm observation of radio-quiet AGNs with ALMA may allow to image the free–free emission of warm photoionized gas in AGNs down to the 30 mas scale, including highly absorbed AGNs.

scholarly journals Estimating supermassive black hole masses in active galactic nuclei using polarization of broad Mg ii, H α, and H β lines

2020 ◽  
Vol 497 (3) ◽  
pp. 3047-3054
Author(s):  
Đorđe Savić ◽  
L Č Popović ◽  
E Shablovinskaya ◽  
V L Afanasiev
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Three Dimensional ◽  
Polarization Plane ◽  
Galactic Nuclei ◽  
Position Angle ◽  
Broad Line ◽  
Keplerian Motion ◽  
Supermassive Black Hole ◽  
Polarization Mechanism

ABSTRACT For type-1 active galactic nuclei (AGNs) for which the equatorial scattering is the dominant broad-line polarization mechanism, it is possible to measure the supermassive black hole (SMBH) mass by tracing the Keplerian motion across the polarization plane position angle φ. So far, this method has been used for 30 objects but only for H α emission line. We explore the possibilities of this method for determining SMBH masses using polarization in broad emission lines by applying it for the first time to Mg ii λ2798 Å spectral line. We use three-dimensional (3-D) Monte Carlo radiative transfer code stokes for simultaneous modelling of equatorial scattering of H α, H β, and Mg ii lines. We included vertical inflows and outflows in the Mg ii broad-line region (BLR). We find that polarization states of H α and H β lines are almost identical and SMBH-mass estimates differ by 7 per cent. For Mg ii line, we find that φ exhibits an additional ‘plateau’ with a constant φ, which deviates than the profiles expected for pure Keplerian motion. SMBH-mass estimates using Mg ii line are higher by up to 35 per cent than those obtained from H α and H β lines. Our model shows that for vertical inflows and outflows in the BLR that are higher or comparable to the Keplerian velocity, this method can be applied as a first approximation for obtaining SMBH mass.

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