scholarly journals A complete disclosure of the hidden type-1 AGN in NGC 1068 thanks to 52 yr of broad-band polarimetric observation

2018 ◽  
Vol 479 (3) ◽  
pp. 3142-3154 ◽  
Author(s):  
F Marin
Keyword(s):  
Broad Band ◽  
Polarimetric Observation ◽  
Ngc 1068

scholarly journals High angular resolution polarimetric imaging of the nucleus of NGC 1068

2021 ◽  
Vol 648 ◽  
pp. A42
Author(s):  
L. Grosset ◽  
D. Rouan ◽  
F. Marin ◽  
D. Gratadour ◽  
E. Lagadec ◽  
...  
Keyword(s):  
Near Infrared ◽  
Angular Resolution ◽  
Broad Band ◽  
Wavelength Dependence ◽  
Single Scattering ◽  
High Angular Resolution ◽  
Monte Carlo Code ◽  
Data Set ◽  
Ngc 1068 ◽  
Inner Region

Context. Polarisation is a decisive method to study the inner region of active galactic nuclei (AGNs) since, unlike classical imaging, it is not affected by contrast issues. When coupled with high angular resolution (HAR), polarisation can help to disentangle the location of the different polarising mechanisms and then give insight into the physics taking place in the core of AGNs. Aims. We obtained a new data set of HAR polarimetric images of the archetypal Seyfert 2 nucleus of NGC 1068 observed with SPHERE/VLT. We aim in this paper to present the polarisation maps and to spatially separate the location of the polarising mechanisms, thereby deriving constraints on the organisation of the dust material in the inner region of this AGN. Methods. With four new narrow-band images between the visible and the near-infrared combined with older broad-band observations, we studied the wavelength dependence of the polarisation properties from 0.7 to 2.2 μm of three selected regions within the inner 2″ surrounding the central engine. We then compared these measurements to radiative transfer simulations of scattering and dichroic absorption processes, using the Monte Carlo code MontAGN. Results. We establish a detailed table of the relative importance of the polarising mechanism as a function of aperture and wavelength. We are able to separate the dominant polarising mechanisms in the three regions of the ionisation cone, the extended envelope of the torus, and the very central bright source of the AGN. Thus, we estimate the contribution of the different polarisation mechanisms to the observed polarisation flux in these regions. Dichroic absorption is estimated to be responsible for about 99% of the polarised flux coming from the photo-centre. However, this contribution would only be restricted to this location because the double-scattering process would be the most important contributor to polarisation in the equatorial plane of the AGN and single scattering is dominant in the polar outflow bi-cone. Conclusions. Even though results are in good agreement with larger apertures measurements, the variety of situations with different mechanisms at play highlights the importance of spatial resolution for the interpretation of polarisation measurements. We also refine the estimation of the integrated optical depth in the visible of the obscuring structure to a range of 20−100, constraining the geometry of the inner region of this AGN.

scholarly journals SkyMapper colours of Seyfert galaxies and Changing-Look AGN

2020 ◽  
Vol 499 (1) ◽  
pp. 1005-1022
Author(s):  
Christian Wolf ◽  
Jacob Golding ◽  
Wei Jeat Hon ◽  
Christopher A Onken
Keyword(s):  
Active Galactic Nuclei ◽  
Power Law ◽  
Stellar Population ◽  
Broad Band ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Host Galaxy ◽  
Normal Galaxies ◽  
Mixing Sequences

ABSTRACT We study the utility of broad-band colours in the SkyMapper Southern Survey for selecting Seyfert galaxies at low luminosity. We find that the u − v index, built from the ultraviolet u and violet v filters, separates normal galaxies, starburst galaxies, and type-1 active galactic nuclei (AGNs). This u − v index is not sensitive to age or metallicity in a stellar population but is instead a quenching-and-bursting indicator in galaxies and detects power-law continua in type-1 AGNs. Using over 25 000 galaxies at z < 0.1 from 6dFGS, we find a selection cut based on u − v and central u band brightness that identifies type-1 AGNs. By eyeballing 6dFGS spectra we classify new Seyfert galaxies of type 1 to 1.8. Our sample includes eight known Changing-Look AGNs (CLAGNs), two of which show such strong variability that they move across the selection cut during the 5 yr of SkyMapper observations in DR3, along mixing sequences of nuclear and host galaxy light. We identify 46 CLAGN candidates in our sample, one of which has been reported as a Type IIn supernova. We show that this transient persists for at least 5 yr and marks a flare in a Seyfert-1 period of a new CLAGN.

scholarly journals A broad-band spectral analysis of eight radio-loud type 1 active galactic nuclei selected in the hard X-ray band

2008 ◽  
Vol 390 (3) ◽  
pp. 1217-1228 ◽  
Author(s):  
M. Molina ◽  
L. Bassani ◽  
A. Malizia ◽  
A. J. Bird ◽  
A. J. Dean ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Active Galactic Nuclei ◽  
Broad Band ◽  
Galactic Nuclei ◽  
X Ray

scholarly journals Infrared Emission from Spiral Galaxy Nuclei

1980 ◽  
Vol 5 ◽  
pp. 173-175
Author(s):  
C. G. Wynn-Williams
Keyword(s):  
Spiral Galaxies ◽  
Broad Band ◽  
Seyfert Galaxy ◽  
Infrared Emission ◽  
Strong Emission ◽  
Physical Size ◽  
Normal Galaxies ◽  
Broad Band Emission ◽  
Band Emission ◽  
Ngc 1068

At the present time we do not know with any certainty what the infrared properties of “normal” galaxies are, although we do know that substantial broad-band emission at 10μm is fairly common in spiral galaxies; Rieke and Lebofsky (1978), for example, were able to detect the nuclei of 16 out of 39 bright spiral galaxies above a level of about 50 mJy. Only one of these, NGC 1068, is a Seyfert Galaxy.With the exception of M31, whose 10μm emission can be accounted for entirely by stellar photospheric emission, all the spiral galaxies detected in Rieke and Lebofsky’s survey show strong emission from heated dust grains. Airborne observations at longer wavelengths (e.g., Telesco and Harper 1980) of a few of these galaxies show a peak in the energy distribution at around 80μm, corresponding to dust temperatures of order 30-60K, while spatial scans, and multi-aperture photometry at 10μm (Rieke 1976; Becklin, Fomalont, and Neugebauer 1973; Becklin et al. 1980) indicate a physical size for the emitting region of a few hundred parsecs diameter.

Crystalloid Inclusions in Hepatocyte Mitochondria and Their Similarity to Cytoplasmic Crystalloids

1974 ◽  
Vol 32 ◽  
pp. 198-199
Author(s):  
Odell T. Minick ◽  
Hidejiro Yokoo
Keyword(s):  
Liver Disease ◽  
Alcoholic Liver Disease ◽  
Special Interest ◽  
Structural Variations ◽  
Mitochondrial Alterations ◽  
The Matrix ◽  
Crystalloid Inclusions ◽  
Liver Biopsies

Mitochondrial alterations were studied in 25 liver biopsies from patients with alcoholic liver disease. Of special interest were the morphologic resemblance of certain fine structural variations in mitochondria and crystalloid inclusions. Four types of alterations within mitochondria were found that seemed to relate to cytoplasmic crystalloids.Type 1 alteration consisted of localized groups of cristae, usually oriented in the long direction of the organelle (Fig. 1A). In this plane they appeared serrated at the periphery with blind endings in the matrix. Other sections revealed a system of equally-spaced diagonal lines lengthwise in the mitochondrion with cristae protruding from both ends (Fig. 1B). Profiles of this inclusion were not unlike tangential cuts of a crystalloid structure frequently seen in enlarged mitochondria described below.

Chronic Laser Exposure Effects on Rabbit Retina

1972 ◽  
Vol 30 ◽  
pp. 54-55
Author(s):  
Burton B. Silver ◽  
Theodore Lawwill
Keyword(s):  
Laser Irradiation ◽  
Laser Light ◽  
Broad Band ◽  
Argon Laser ◽  
Atropine Sulfate ◽  
Ultrastructural Changes ◽  
Laser Exposure ◽  
Rabbit Retina ◽  
Histological Changes ◽  
Threshold Doses

Dutch-belted 1 to 2.5 kg anesthetized rabbits were exposed to either xenon or argon laser light administered in a broad band, designed to cover large areas of the retina. For laser exposure, the pupil was dilated with atropine sulfate 1% and pheny lephrine 10%. All of the laser generated power was within a band centered at 5145.0 Anstroms. Established threshold for 4 hour exposures to laser irradiation are in the order of 25-35 microwatts/cm2. Animals examined for ultrastructural changes received 4 hour threshold doses. These animals exhibited ERG, opthalmascopic, and histological changes consistent with threshold damage.One month following exposure the rabbits were killed with pentobarbitol. The eyes were immediately enucleated and dissected while bathed in 3% phosphate buffered gluteraldehyde.

Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

1978 ◽  
Vol 36 (1) ◽  
pp. 658-659
Author(s):  
G.J.C. Carpenter
Keyword(s):  
Elevated Temperature ◽  
Strain Field ◽  
Zirconium Hydride ◽  
Zirconium Atom ◽  
Atom Diffusion ◽  
Solvus Temperature ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

Direct structure images of 30° partial dislocation cores in silicon

1987 ◽  
Vol 45 ◽  
pp. 242-243
Author(s):  
J. C. Barry ◽  
H. Alexander
Keyword(s):  
Dislocation Core ◽  
Preparation Technique ◽  
Burgers Vector ◽  
Vector Type ◽  
Sample Preparation Technique ◽  
Lattice Images ◽  
Dislocation Core Structure ◽  
Type Lattice ◽  
Direct Inspection

Dislocations in silicon produced by plastic deformation are generally dissociated into partials. 60° dislocations (Burgers vector type 1/2[101]) are dissociated into 30°(Burgers vector type 1/6[211]) and 90°(Burgers vector type 1/6[112]) dislocations. The 30° partials may be either of “glide” or “shuffle” type. Lattice images of the 30° dislocation have been obtained with a JEM 100B, and with a JEM 200Cx. In the aforementioned experiments a reasonable but imperfect match was obtained with calculated images for the “glide” model. In the present experiment direct structure images of 30° dislocation cores have been obtained with a JEOL 4000EX. It is possible to deduce the 30° dislocation core structure by direct inspection of the images. Dislocations were produced by compression of single crystal Si (sample preparation technique described in Alexander et al.).

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