scholarly journals A Study of the Continua of the Nuclei of Galaxies

1972 ◽  
Vol 44 ◽  
pp. 188-189
Author(s):  
D. Alloin ◽  
Y. Andrillat ◽  
S. Souffrin
Keyword(s):  
Continuous Spectrum ◽  
Stellar Population ◽  
Absorption Lines ◽  
Ngc 1068 ◽  
Instrumental Effect

Many people have attacked the problem of synthesizing the stellar population of the galaxies. We have performed such a synthesis, by using only the intensities of absorption lines in the nuclei of galaxies. It is then possible to obtain a synthesized continuous spectrum even if there are several possible solutions for the stellar composition, and the computed continuum does not vary much with the assumed model of stellar population.The method is to fit the equivalent widths of the absorption lines using different stellar compositions. In order to avoid any instrumental effect, we have observed different lines and bands from 3500 to 8500 å in stars of various well-known stellar types and luminosity classes, under the same conditions as the galaxies.We have applied this method to some ‘ordinary’ nuclei and to some Seyfert ones. As an example, we show the results for M81 and for NGC 1068.

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 Determination of the OB Stellar Population of IZw18 on the Basis of its Hγ and Hδ Absorption lines

1999 ◽  
Vol 194 ◽  
pp. 444-447
Author(s):  
A. Sinanyan ◽  
D. Kunth ◽  
J. Lequeux ◽  
G. Comte ◽  
A. Petrosian
Keyword(s):  
Spectral Range ◽  
Stellar Population ◽  
Dwarf Galaxy ◽  
Absorption Lines ◽  
Spectroscopic Observations ◽  
Narrow Spectral Range ◽  
Blue Compact Dwarf Galaxy

On the basis of new spectroscopic observations of the blue compact dwarf galaxy IZw18 in the narrow spectral range between 4000Å and 4500Å absorption components of Hγ and Hδ lines were discovered. Equivalent widths of Hγ and Hδ lines have been measured. From available data the OB population of IZw18 was analyzed.

scholarly journals Nuclear and extended spectra of NGC 1068 - II. Near-infrared stellar population synthesis

2010 ◽  
Vol 406 (4) ◽  
pp. 2185-2192 ◽  
Author(s):  
Lucimara P. Martins ◽  
Rogério Riffel ◽  
Alberto Rodríguez-Ardila ◽  
Ruth Gruenwald ◽  
Ronaldo de Souza
Keyword(s):  
Stellar Population ◽  
Near Infrared ◽  
Population Synthesis ◽  
Stellar Population Synthesis ◽  
Ngc 1068

scholarly journals 53. On the nature of the emission from the galaxy NGC 4486

1958 ◽  
Vol 6 ◽  
pp. 517-519
Author(s):  
I. S. Shklovsky
Keyword(s):  
Continuous Spectrum ◽  
Radio Galaxy ◽  
Absorption Lines ◽  
The Galaxy

As is known, a striking peculiarity of the radio galaxy NGC 4486 is the presence of a small and very bright ‘jet’ in its central part. As it seems to us, the key to the understanding of the nature of the radio galaxy NGC 4486 is the purely continuous spectrum of the above jet, where not even a slightest trace or emission or absorption lines is present.

scholarly journals The SLUGGS survey: globular cluster stellar population trends from weak absorption lines in stacked spectra

2014 ◽  
Vol 446 (1) ◽  
pp. 369-390 ◽  
Author(s):  
Christopher Usher ◽  
Duncan A. Forbes ◽  
Jean P. Brodie ◽  
Aaron J. Romanowsky ◽  
Jay Strader ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Stellar Population ◽  
Population Trends ◽  
Absorption Lines ◽  
Weak Absorption

scholarly journals 36. On the nature of the emission from the Galaxy NGC4486

1957 ◽  
Vol 4 ◽  
pp. 205-207 ◽  
Author(s):  
I. S. Shklovsky
Keyword(s):  
Continuous Spectrum ◽  
Radio Galaxy ◽  
Absorption Lines ◽  
The Galaxy

It is well known that the radio galaxy NGC4486 has as a striking peculiarity a small and very bright ‘jet’ in its central part. It seems to us that the key to the understanding of the nature of this radio galaxy is the purely continuous spectrum of the jet, where not even a slight trace of emission or absorption lines is present.

scholarly journals New insights on the central stellar population and gas outflow in NGC 1068 from YJH spectroscopy with SPHERE/VLT

2019 ◽  
Vol 629 ◽  
pp. A98 ◽  
Author(s):  
Pierre Vermot ◽  
Yann Clénet ◽  
Damien Gratadour
Keyword(s):  
Central Region ◽  
Stellar Population ◽  
Near Infrared ◽  
Scattered Light ◽  
Emission Lines ◽  
Continuum Emission ◽  
Central Engine ◽  
Ngc 1068 ◽  
Radial Outflow ◽  
Three Components

Aims. We characterise the properties of stars, dust, and gas and their spatial distribution in the central region of the Seyfert 2 galaxy NGC 1068. Method. Our study is based on near-infrared (YJH, 0.95−1.650 μm, R = 350) long-slit spectroscopy observations of the central region of NGC 1068 with a 0.4″ spatial resolution. We decomposed the observed continuum emission into three components: hot dust, stars, and scattered light from the central engine. We measured their contributions at various distances from the nucleus. We also measured fluxes and Doppler shifts for the emission lines in our spectrum to probe the physical conditions of the narrow line region. Results. Dust and stars are the main sources of continuum emission, but scattered light from the central engine has also been detected in the very central region. Together, these three components reproduce the observed continuum well. The dust emission is compatible with a 830 K blackbody. It has only been detected in the very central region and is not spatially resolved. The stellar content is ubiquitous. It harbours a 250 pc cusp centred around the nucleus, over-imposed on a young stellar background. The spectrum of the cusp is consistent with a 120 Myr old single stellar population. Finally, the emission lines exhibit a significant Doppler shift that is consistent with a radial outflow from the nucleus in a biconical structure. The [Fe II] behaviour strongly differs from other lines, indicating that it arises from a different structure.

scholarly journals Optical Spectra of Extragalactic Radio Sources

1968 ◽  
Vol 1 ◽  
pp. 356-360
Author(s):  
E. Margaret Burbidge
Keyword(s):  
Stellar Population ◽  
Velocity Dispersion ◽  
Absorption Lines ◽  
Radio Sources ◽  
Extragalactic Radio Sources ◽  
Band Filter ◽  
Stellar Velocity ◽  
Narrow Band Filter ◽  
Minimum Age ◽  
Filter Photometry

Extragalactic radio sources can be grouped spectroscopically into those that show absorption lines produced by a stellar population (e.g. the nearer radio galaxies, and some more distant ones, usually of D or E type) and those that show only lines (usually in emission) produced by low-density gas (e.g. QSO’s and many N-type galaxies). If absorption lines from stars are present, one can estimate a minimum age from the stellar population, and perhaps a mass for the system from the stellar velocity dispersion. If no spectroscopic evidence on the stellar population is available (and this includes evidence from narrow-band filter photometry), then we have much less hold on the problems of age and evolutionary state. Absence of stellar absorption lines does not necessarily mean that stars are absent, but simply that their light, if present, does not contribute appreciably to the overall optical spectrum.

Spektrum explodierender Drähte in verschiedenen Atmosphären. Messung des Dissoziationsgrades des umgebenden Gases und des Drucks im Plasma/Spectrum of Exploding Wires within Different Atmospheres. Measure of Dissociation Rate of Surrounding Gas and of Plasma Pressure

1976 ◽  
Vol 31 (5) ◽  
pp. 503-504
Author(s):  
C. Triché ◽  
G. Perarnau
Keyword(s):  
Continuous Spectrum ◽  
Absorption Line ◽  
Copper Wire ◽  
Plasma Pressure ◽  
Dissociation Rate ◽  
Absorption Lines ◽  
Exploding Wires ◽  
Degree Of Dissociation ◽  
Characteristic Emission ◽  
Plasma Spectrum

Abstract The explosion of a copper wire is caused by means of a discharge from a pulsed source. We observe a continuous spectrum with characteristic emission and absorption lines. The degree of dissociation of the surrounding gas and the pressure of the plasma can be determined from the width of an absorption line.

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

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