Excitation of the Optical Emission Lines in Quasi-Stellar Radio Sources

1966 ◽  
Vol 143 ◽  
pp. 268 ◽  
Author(s):  
Donald E. Osterbrock ◽  
Robert A. R. Parker
Keyword(s):  
Optical Emission ◽  
Emission Lines ◽  
Radio Sources

scholarly journals The Impact of the Early Stages of Radio Source Evolution on the ISM of the Host Galaxies

2003 ◽  
Vol 20 (1) ◽  
pp. 129-133 ◽  
Author(s):  
R. Morganti ◽  
C. N. Tadhunter ◽  
T. A. Oosterloo ◽  
J. Holt ◽  
A. Tzioumis ◽  
...  
Keyword(s):  
Radio Source ◽  
Radio Galaxy ◽  
Optical Emission ◽  
The Other ◽  
Emission Lines ◽  
Radio Sources ◽  
Host Galaxies ◽  
Cygnus A ◽  
Intermediate Size ◽  
The Impact

AbstractThe study of both neutral and ionised gas in young radio sources is providing key information on the effect the radio plasma has on the ISM of these objects. We present results obtained for the compact radio sources PKS 1549–79, 4C 12.50 and PKS 1814–63 and for the intermediate-size radio galaxy 3C 459. At least in the first two, low ionisation optical emission lines and HI absorption appear to be associated with the extended, but relatively quiescent, dusty cocoon surrounding the nucleus. The [OIII] lines are, on the other hand, mostly associated with the region of interaction between the radio plasma and the ISM, indicating a fast outflow from the centre. A case of fast outflow (up to ∼1000 km s-1) is also observed in HI in the radio source 4C 12.50. As the radio source evolves, any obscuring material along the radio axis is swept aside until, eventually, cavities (of the same kind as observed e.g. in Cygnus A) are hollowed out on either side of the nucleus. We may witness this phase in the evolution of a radio source in the radio galaxy 3C 459.

scholarly journals Compact Radio Sources in the Nuclei of Elliptical Galaxies

1972 ◽  
Vol 44 ◽  
pp. 222-223 ◽  
Author(s):  
R. D. Ekers
Keyword(s):  
Radio Emission ◽  
Angular Size ◽  
Optical Emission ◽  
Elliptical Galaxies ◽  
Emission Lines ◽  
Radio Sources ◽  
Radio Luminosity ◽  
Compact Source ◽  
Extended Radio

Ten percent of the intrinsically bright elliptical galaxies contain compact radio sources (angular size < 3 arc sec) with radio luminosity ∼ 1040 erg s−1. The presence of a compact source is correlated with the presence of extended radio emission and with the presence of optical emission lines.

scholarly journals Low-Luminosity Active Nuclei in Elliptical Galaxies

1987 ◽  
Vol 121 ◽  
pp. 443-450
Author(s):  
Elaine M. Sadler
Keyword(s):  
Optical Emission ◽  
Radio Galaxies ◽  
Elliptical Galaxies ◽  
Emission Lines ◽  
Gas Content ◽  
Radio Sources ◽  
Simple Relationship ◽  
Early Type ◽  
Optical Emission Spectrum ◽  
Radio Power

The results of a sensitive radio and optical survey of nearby early-type galaxies show that most (perhaps all) bright ellipticals have ‘active’ nuclei. These are characterized by a central non-thermal radio source and a weak LINER-like optical emission spectrum. There appears to be a smooth continuity in optical and radio properties from the weakest nearby sources to strong radio galaxies. Galaxies with radio sources usually show optical emission lines, but there is no simple relationship between gas content and radio power.

scholarly journals Infrared Observations of Radio Galaxies

1982 ◽  
Vol 97 ◽  
pp. 239-246
Author(s):  
George H. Rieke
Keyword(s):  
Thermal Emission ◽  
Optical Emission ◽  
Seyfert Galaxies ◽  
Radio Sources ◽  
Extragalactic Radio Source ◽  
Extragalactic Source ◽  
Infrared Observations ◽  
Infrared Studies ◽  
Complete Identification ◽  
Ultraviolet Photons

For technical reasons, infrared studies of active galaxies have lagged far behind optical and radio ones. This is unfortunate, since entirely new aspects of these sources are often revealed in the infrared. The extreme efficiency of dust at degrading ultraviolet photons into cool thermal emission frequently makes the luminosity of an extragalactic source inaccessible to optical and radio astronomers. At the same time, the effects of dust on optical emission line ratios and continuum shapes can be profound. The complete identification of samples of radio sources will require infrared observations to supplement the optical techniques now generally employed, and the extreme properties of the sources bright in the infrared can provide new insights to conditions in extragalactic nonthermal sources. To illustrate these points, I will discuss three cases: 1.) galaxies undergoing a powerful burst of star formation, 2.) intermediate type Seyfert galaxies, and 3.) an extreme infrared identification of an extragalactic radio source.

scholarly journals Molecular gas around the Wolf-Rayet star WR 18 (WN4)

2003 ◽  
Vol 212 ◽  
pp. 732-733
Author(s):  
Anthony P. Marston
Keyword(s):  
Mass Loss ◽  
Optical Emission ◽  
Emission Lines ◽  
Molecular Gas ◽  
Evolved Stars ◽  
Ring Nebula ◽  
History Of ◽  
Optical Ring ◽  
Ring Nebulae ◽  
Rayet Star

Optically observed ring nebulae and H i cavities around Wolf-Rayet stars have enabled us to obtain information on the history of mass-loss associated with these massive evolved stars. However, such studies have left a number of unanswered questions regarding the amount of mass-loss and the conditions of the stars during a sequence of mass-loss phases. Here we discuss the molecular gas environments of the WR star WR 18, which has an associated optical ring nebula NGC 3199. Our observations show that significant amounts of molecular gas appear close to and associated with the star. Mapping of molecular CO near the star shows that molecular materials appear to substantially avoid areas of optical emission and, instead, form a distorted clumpy shell interior to NGC 3199. Molecular emission lines are broader than lines seen in the interstellar medium and suggest the shell is composed of ejecta. This is further corroborated by the enhanced abundances of molecules containing C, N and O. Implications of the observations for the evolution of WR 18 are discussed.

scholarly journals Filtered CCD images of southern Herbig-Haro objects

1987 ◽  
Vol 122 ◽  
pp. 189-190
Author(s):  
B. Whitmore ◽  
D.H.M. Cameron ◽  
R.F. Warren-Smith
Keyword(s):  
High Velocity ◽  
Optical Emission ◽  
Emission Lines ◽  
Ccd Cameras ◽  
Hh Objects

It is currently believed that Herbig-Haro (HH) objects are a consequence of a high-velocity (up to at least 200 km s−1) outflow of material from a young embedded star. These flows can often be detected by deep observations of optical emission lines using CCD cameras.

scholarly journals Colliding Stellar Winds in O-type Close Binary Systems

1992 ◽  
Vol 135 ◽  
pp. 146-148
Author(s):  
D.R. Gies ◽  
M.S. Wiggs
Keyword(s):  
Binary Systems ◽  
Optical Emission ◽  
Emission Lines ◽  
Optical Observations ◽  
Close Binary ◽  
High Dispersion ◽  
Stellar Winds ◽  
Close Binary Systems ◽  
Circumstellar Gas ◽  
The Individual

In close binary systems of O-type stars, the individual stellar winds will collide between the stars to form shock fronts (Stevens et al. 1992). Binaries with equally luminous stars will have winds of comparable strength, and the shock will occur near the mid-plane between the stars, but in binaries of unequal luminosity, the interaction will occur along a bow shock wrapped around the star with the weaker wind. The presence of the shock region can be detected through excess X-ray emission (Chlebowski & Garmany 1990), and orbital phase-related variations in the UV P Cygni lines (Shore & Brown 1988) and optical emission lines (formed in high density regions of circumstellar gas).We have begun a search for colliding winds through a study of the optical emission lines and UV P Cygni lines in four massive binaries, AO Cas (Gies & Wiggs 1991), Plaskett’s star = HD 47129 (Wiggs & Gies 1992), 29 UW CMa and ι Ori. The optical observations consist of high S/N spectra of the Hα and He I λ6678 region obtained with the University of Texas McDonald Observatory 2.1-m telescope and coudé Reticon system. The UV observations were culled from archival IUE high dispersion spectra of several P Cygni features (N V λ1240, Si IV λ1400, C IV λ1550).

scholarly journals Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas

2020 ◽  
Vol 6 (27) ◽  
pp. eaay9711 ◽  
Author(s):  
D. Krishnarao ◽  
R. A. Benjamin ◽  
L. M. Haffner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Hydrogen Gas ◽  
Emission Lines ◽  
Neutral Gas ◽  
Optical Line ◽  
Tilted Disk

Optical emission lines are used to categorize galaxies into three groups according to their dominant central radiation source: active galactic nuclei, star formation, or low-ionization (nuclear) emission regions [LI(N)ERs] that may trace ionizing radiation from older stellar populations. Using the Wisconsin H-Alpha Mapper, we detect optical line emission in low-extinction windows within eight degrees of Galactic Center. The emission is associated with the 1.5-kiloparsec-radius “Tilted Disk” of neutral gas. We modify a model of this disk and find that the hydrogen gas observed is at least 48% ionized. The ratio [NII] λ6584 angstroms/Hα λ6563 angstroms increases from 0.3 to 2.5 with Galactocentric radius; [OIII] λ5007 angstroms and Hβ λ4861 angstroms are also sometimes detected. The line ratios for most Tilted Disk sightlines are characteristic of LI(N)ER galaxies.

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