scholarly journals Structure

1968 ◽  
Vol 34 ◽  
pp. 456-462 ◽  
Author(s):  
R. Minkowski
Keyword(s):  
Near Infrared ◽  
Planetary Nebulae ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Brightness Distribution ◽  
Line Intensities ◽  
Near Ultraviolet ◽  
Ngc 7027 ◽  
Expansion Pattern ◽  
Ngc 1068

My first task is to give summaries of the sessions on observations of the spectra of planetary nebulae and on the spectra of the central stars.About the spectra of planetary nebulae there is little more to say than that the observations of line intensities in the range from the near ultraviolet to the near infrared have made impressive progress. Most important is the extension of the observations into the infrared which has led to the discovery by Gillet, Low and Stein of unexpectedly high intensities in the continuous spectrum of NGC 7027 between 4μ and 14μ (75 to 22 THz). In this respect NGC 7027 and the Seyfert galaxy NGC 1068 resemble each other. Similarity of the compositions of the emission-line spectra of these two objects has been noted long ago; some lines of low ionization – [O II], [S II] –, however, are stronger in the Seyfert galaxies. The physical significance of the similarity of the infrared continua is not clear at this time, but I see no reason to reject the classification of NGC 7027 as a planetary nebula. It has a very irregular brightness distribution with much structure, but an outline which is roughly elliptical and the usual expansion pattern with a velocity of expansion of 21 km/sec.

A Study of the Seyfert Galaxy NGC 4151

1967 ◽  
Vol 1 (1) ◽  
pp. 7-7 ◽  
Author(s):  
J. B. Oke ◽  
Wallace L. W. Sargent
Keyword(s):  
Continuous Spectrum ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Radio Galaxies ◽  
Emission Lines ◽  
Ngc 4151 ◽  
Broad Emission ◽  
Ngc 1068 ◽  
Stellar Sources ◽  
No Absorption

The small group of known Seyfert galaxies (Seyfert 1943) is of interest because it is clear that some violent activity is occurring in the nucleus, and some of the properties suggest a relationship with quasi-stellar sources. The spectrum of a Seyfert galaxy consists of strong, often very broad, emission lines superposed on a continuous spectrum which in some cases shows no absorption-line features. Two of the galaxies, NGC 1068 and 1275, are radio galaxies and the latter is known to be variable at radio frequencies (Dent 1966).

scholarly journals Planetary Nebulae and Seyfert Galaxies - Similarities and Differences

1983 ◽  
Vol 103 ◽  
pp. 473-486 ◽  
Author(s):  
Donald E. Osterbrock
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Planetary Nebulae ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Broad Line ◽  
Tentative Model ◽  
Input Spectrum ◽  
Similarities And Differences ◽  
Galaxy Nucleus

Knowledge gained in the study of planetary nebulae has been, and can be further, transferred to understanding active galactic nuclei. Photoionization is the main energy-input mechanism in the narrow-line regions, and probably although by no means certainly in the broad-line regions as well. There are many detailed differences because of the much “harder” input spectrum in active galactic nuclei, compared with planetary nebulae. A tentative model of the structure of the gas distribution in a Seyfert-galaxy nucleus is presented.

scholarly journals Near Infrared Emission of Neutral Carbon from Photon-Dominated Regions

1992 ◽  
Vol 150 ◽  
pp. 333-334
Author(s):  
V. Escalante ◽  
A. Sternberg ◽  
A. Dalgarno
Keyword(s):  
Field Intensity ◽  
Radiative Recombination ◽  
Near Infrared ◽  
Planetary Nebulae ◽  
Infrared Emission ◽  
Emission Lines ◽  
Radiation Fields ◽  
Ngc 7027 ◽  
Near Infrared Emission ◽  
Intense Radiation

Detailed calculations are reported of the intensities of the near infrared forbidden lines of neutral carbon atoms at λ 985.0 nm, 982.3 nm and 872.7 nm emitted from dense clouds subjected to intense radiation fields. The metastable levels that produce the lines are excited by radiative recombination of the C+ ions produced by photoionization. Impacts of electrons with C atoms in the heated edge zones of the clouds contribute an insignificant part to the excitation. The lines observed in M42 and NGC 2024 can be interpreted as arising in gas with densities in excess of 105 cm−3 and radiation fields with intensities between 103 and 106 times the average interstellar field intensity. Radiative recombination of C+ ions may also be an important source of the emission lines detected in the planetary nebulae NGC 6270 and NGC 7027.

High-density gas in bipolar outflow sources and active galactic nuclei

1986 ◽  
Vol 64 (4) ◽  
pp. 421-425 ◽  
Author(s):  
S. E. Persson
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Near Infrared ◽  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Detailed Comparison ◽  
Seyfert Galaxies ◽  
High Density ◽  
Young Stellar Objects ◽  
Molecular Outflow

The highest density regions near the base of the outflow in young stellar objects with bipolar molecular outflows are discussed. Bright emission lines of Ca II and O I characterize the spectra and lead to estimates of n ~ 1010 cm−3, temperatures of a few thousand Kelvins, and mass motions of several hundred kilometres per second. Typically the rate of momentum transfer within this region fails by more than an order of magnitude to provide the force necessary to drive the molecular outflow on the parsec scale. The overall near-infrared spectra of these young stars are similar to those of certain active galactic nuclei having strong Fe II emission.A comparison is made between the Ca II and O I lines in the infrared core source of the bipolar H II region S106 and in the Seyfert galaxy Mrk 42. The spectra are shown to be scaled versions of each other, and we conclude that the physical conditions are broadly similar in the high-density emission-line regions of these two objects. The Ca II lines appear self-reversed in both objects, but possible Ca II absorption in the underlying galaxy in Mrk 42 compromises the detailed comparison of line shapes. Nevertheless, it is likely that the geometries and velocity fields are also analogous. Derived parameters of the emission-line regions in S106 and the Seyfert galaxies I Zw 1 and Mrk 42 are compared.

scholarly journals Mid-Infrared Forbidden Lines of NGC 1068, NGC 4151, and NGC 5506

1997 ◽  
Vol 159 ◽  
pp. 308-309
Author(s):  
M.A. Greenhouse ◽  
T.L. Hayward ◽  
S. Satyapal ◽  
D.H. Wooden ◽  
J.W. Miles ◽  
...  
Keyword(s):  
Near Infrared ◽  
Seyfert Galaxies ◽  
Line Profiles ◽  
Mid Infrared ◽  
Ngc 4151 ◽  
Faint Object ◽  
Excitation Potential ◽  
Ngc 1068 ◽  
Infrared Array ◽  
Faint Object Spectrograph

We report near-infrared spectroscopy of three Seyfert galaxies. Velocity resolved spectra covering low excitation-potential transitions of [Ar III] 8.991 µm, [S IV] 10.514 µm, and [Ne II] 12.813 µm were obtained using the facility mid-infrared array spectrometer (SpectroCam) of the Palomar Observatory Hale 5-m Telescope, and low-resolution spectra covering [Mg V] 5.608 µm, [Ar II] 6.985 µm, and [Ne VI] 7.642 µm were obtained using the faint-object spectrograph (HIFOGS) of the Kuiper Airborne Observatory (KAO).We find high contrast [Ar III] and [S IV] in each galaxy, and [Ne II] in NGC 1068 and NGC 4151 (12.8 µm data were not obtained on NGC 5506). The line profiles are well resolved. In NGC 1068 and NGC 4151, they are fit by singlecomponent Gaussians. However, in NGC 5506, evidence for a broad pedestal is seen in the [Ar III] and [S IV] spectra, similar to the broad Paβ component reported by Blanco et al. (1990) and Rix et al. (1990).

scholarly journals Obscuring and Feeding Supermassive Black Holes with Evolving Nuclear Star Clusters

2009 ◽  
Vol 5 (S267) ◽  
pp. 307-312
Author(s):  
M. Schartmann ◽  
A. Burkert ◽  
M. Krause ◽  
M. Camenzind ◽  
K. Meisenheimer ◽  
...  
Keyword(s):  
High Resolution ◽  
Adaptive Optics ◽  
Large Scale ◽  
Near Infrared ◽  
Star Clusters ◽  
Seyfert Galaxies ◽  
Disk Model ◽  
Ngc 1068 ◽  
Hydrodynamical Simulations ◽  
Integral Field Spectrograph

AbstractRecently, high-resolution observations made with the help of the near-infrared adaptive optics integral field spectrograph SINFONI at the VLT proved the existence of massive and young nuclear star clusters in the centers of a sample of Seyfert galaxies. With the help of high-resolution hydrodynamical simulations with the pluto code, we follow the evolution of such clusters, especially focusing on mass and energy feedback from young stars. This leads to a filamentary inflow of gas on large scales (tens of parsecs), whereas a turbulent and very dense disk builds up on the parsec scale. Here we concentrate on the long-term evolution of the nuclear disk in NGC 1068 with the help of an effective viscous disk model, using the mass input from the large-scale simulations and accounting for star formation in the disk. This two-stage modeling enables us to connect the tens-of-parsecs scale region (observable with SINFONI) with the parsec-scale environment (MIDI observations). At the current age of the nuclear star cluster, our simulations predict disk sizes of the order 0.8 to 0.9 pc, gas masses of order 106M⊙, and mass transfer rates through the inner boundary of order 0.025 M⊙yr−1, in good agreement with values derived from observations.

scholarly journals Collisional Excitation of the 10830 He I Line and the Population of the 23S He I State in Gaseous Nebulae

1989 ◽  
Vol 131 ◽  
pp. 212-212
Author(s):  
M. Peimbert ◽  
S. Torres-Peimbert
Keyword(s):  
Optical Depth ◽  
Planetary Nebulae ◽  
H Ii Regions ◽  
Type I ◽  
Line Intensities ◽  
Gaseous Nebulae ◽  
Radiative Transitions ◽  
Ngc 7027 ◽  
Ngc 7662 ◽  
Dust Absorption

From the study of the λλ5876, 7065 and 10830 He I line intensities in NGC 6572, NGC 6803, NGC 7009, NGC 7027, NGC 7662 and IC 418, it is found that the I(10830)/I(5876) ratio is weaker than expected. By considering estimates of the optical depth at λ10830 due to dust absorption and by determining the optical depth at λ10830 due to atomic absorption, it is argued that dust absorption of λ(10830) photons is not the cause for the low I(10830)/I(5876) ratios. By assuming that the 23S He0 state is depopulated only by radiative transitions to the 11S state and by triplet-singlet exchange collisions, it is found that its population is about a factor of two smaller than expected. This result is in agreement with a previous study of the λ3889, 4472, 5876, 6678 and 7065 line intensities in a group of thirteen Type I planetary nebulae. One of the main implications of the underpopulation of the 23S level is that the collisional effects in the N(He)/N(H) abundance ratios of planetary nebulae and 0-poor extragalactic H II regions are smaller than previously thought.

scholarly journals High-energy Neutrinos from Magnetized Coronae of Active Galactic Nuclei and Prospects for Identification of Seyfert Galaxies and Quasars in Neutrino Telescopes

2021 ◽  
Vol 922 (1) ◽  
pp. 45
Author(s):  
Ali Kheirandish ◽  
Kohta Murase ◽  
Shigeo S. Kimura
Keyword(s):  
Galactic Nuclei ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
High Energy ◽  
X Rays ◽  
Neutrino Telescopes ◽  
Neutrino Detectors ◽  
Ngc 1068 ◽  
High Energy Neutrinos ◽  
Promising Source

Abstract Particles may be accelerated in magnetized coronae via magnetic reconnections and/or plasma turbulence, leading to high-energy neutrinos and soft γ-rays. We evaluate the detectability of neutrinos from nearby bright Seyfert galaxies identified by X-ray measurements. In the disk-corona model, we find that NGC 1068 is the most promising Seyfert galaxy in the Northern sky, where IceCube is the most sensitive, and show prospects for the identification of aggregated neutrino signals from Seyfert galaxies bright in X-rays. Moreover, we demonstrate that nearby Seyfert galaxies are promising targets for the next generation of neutrino telescopes such as KM3NeT and IceCube-Gen2. For KM3NeT, Cen A can be the most promising source in the Southern sky if a significant fraction of the observed X-rays come from the corona, and it could be identified in few years of KM3NeT operation. Our results reinforce the idea that hidden cores of supermassive black holes are the dominant sources of the high-energy neutrino emission and underlines the necessity of better sensitivity to medium-energy ranges in future neutrino detectors for identifying the origin of high-energy cosmic neutrinos.

An Infrared Microscope for Use on a Focused Ion Beam for Circuit Edit and Backside Edit Applications

2015 ◽  
Author(s):  
Alexander Richards ◽  
Matthew Weschler ◽  
Michael Durller
Keyword(s):  
Focused Ion Beam ◽  
Near Infrared ◽  
Ion Beam ◽  
Visible Spectrum ◽  
Camera System ◽  
Buried Structures ◽  
Ir Camera ◽  
Area Of Interest ◽  
Near Ultraviolet ◽  
Infrared Microscope

Abstract To help solve the navigational problem, i.e., being able to successfully locate a circuit for probing or editing without destroying chip functionality, a near-infrared (NIR), near-ultraviolet (NUV), and visible spectrum camera system was developed that attaches to most focused ion beam (FIB) or scanning electron microscope vacuum chambers. This paper reviews the details of the design and implementation of the NIR/NUV camera system, as instantiated upon the FEI FIB 200, with a particular focus on its use for the visualization of buried structures, and also for non-destructive real time area of interest location and end point detection. It specifically considers the use of the micro-optical camera system for its benefit in assisting with frontside and backside circuit edit, as well as other typical FIB milling activities. The quality of the image obtained by the IR camera rivals or exceeds traditional optical based imaging microscopy techniques.

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