The optical variability of the Seyfert galaxies NGC 4051 and NGC 1068

1996 ◽  
Vol 235 (2) ◽  
pp. 255-262
Author(s):  
Y. H. Zhang ◽  
G. Z. Xie ◽  
S. L. Cao ◽  
K. H. Li ◽  
J. C. Wang ◽  
...  
Keyword(s):  
Seyfert Galaxies ◽  
Optical Variability ◽  
Ngc 1068 ◽  
Ngc 4051

scholarly journals Radio Observations of Neutral Hydrogen in Four Seyfert Galaxies

1972 ◽  
Vol 44 ◽  
pp. 269-270
Author(s):  
Ronald J. Allen ◽  
Bernard F. Darchy ◽  
Robert Lauqué
Keyword(s):  
Total Mass ◽  
Large Scale ◽  
Neutral Hydrogen ◽  
Seyfert Galaxies ◽  
Optical Spectra ◽  
Optical Data ◽  
Ngc 4151 ◽  
Ngc 1068 ◽  
Ngc 4051 ◽  
Radial Outflow

The 21-cm wavelength radiation from neutral hydrogen in NGC 1068, NGC 3227, NGC 4051 and NGC 4151 has been observed with the large radio telescope at Nanĉay, France. Since the angular sizes of these galaxies are of the same order as the telescope right ascension beam-width, no information on the angular distribution of the neutral hydrogen was obtained. However the radial velocity distribution of the total hydrogen (the ‘integrated profile’) of the whole galaxy was measured for each of the four galaxies. The hydrogen masses and total masses can be calculated from these profiles using simple models of galaxy shapes and rotation curves.Optical spectra sometimes show evidence for explosive phenomena and radial outflow of gas in the central regions of Seyfert galaxies. We have examined the integrated radio profiles for indications of large-scale radial motions of neutral hydrogen in two ways. First, for all four galaxies observed, we compare the ratios of hydrogen mass to total mass with the values obtained from other galaxies (not Seyfert) of the same morphological type. Second, for these galaxies where the optical data are available, we compare the estimates of total mass obtained from the optical spectra with the estimates based on the width of the radio profile.We conclude from these comparisons that the integrated profile of NGC 1068 is unusually broad. One possible interpretation which is qualitatively consistent with the optical data is that an appreciable fraction (about ⅓) of the neutral hydrogen content of NGC 1068 is moving radially outward with velocities of about 200 km s−1 An indication of similar phenomena (although less extreme) is obtained for NGC 4051. The widths of the integrated profiles of NGC 3227 and NGC 4151 do not seem unusual.

TRGB Distances to Seyfert Galaxies NGC 1068, NGC 3227, NGC 4051, and NGC 4151

2021 ◽  
Vol 76 (3) ◽  
pp. 255-268
Author(s):  
N. A. Tikhonov ◽  
O. A. Galazutdinova
Keyword(s):  
Seyfert Galaxies ◽  
Ngc 4151 ◽  
Ngc 1068 ◽  
Ngc 4051

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 Survey of Milliarcsec Structure in Eight Seyfert Galaxies: Results on NGC 1068 and NGC 4151

1998 ◽  
Vol 164 ◽  
pp. 301-302 ◽  
Author(s):  
A. L. Roy ◽  
J. S. Ulvestad ◽  
E. J. M. Colbert ◽  
A. S. Wilson ◽  
R. P. Norris
Keyword(s):  
Spectral Index ◽  
Low Frequency ◽  
Seyfert Galaxies ◽  
Scale Structure ◽  
Scale Morphology ◽  
Ngc 4151 ◽  
Ngc 1068

AbstractWe are surveying eight nearby Seyfert galaxies (four Sy1s and four Sy2s) that have compact radio cores, using the VLBA. We are interested in parsec-scale morphology and low-frequency absorption effects, and so are observing four frequencies (1.6, 4.8, 8.4 and 15 GHz) to get spectral-index diagnostics. In this paper, we present results on two galaxies, NGC 1068 and NGC 4151. NGC 4151 shows a curved radio jet on the sub-parsec scale, with the smallest scale structure misaligned by 55° from the jet on scales of parsecs to hundreds of parsecs. NGC 1068 contains several components in the inner tens of parsecs, with those components showing a variety of absorption and resolution effects.

Photoproduction of gravitational radiation by some astrophysical objects

1976 ◽  
Vol 54 (1) ◽  
pp. 76-79 ◽  
Author(s):  
G. Papini ◽  
S.-R. Valluri
Keyword(s):  
Neutron Stars ◽  
Electromagnetic Fields ◽  
Gravitational Radiation ◽  
Galactic Center ◽  
Seyfert Galaxies ◽  
The Sun ◽  
Ngc 4151 ◽  
Astrophysical Objects ◽  
Ngc 1068

Estimates are given for the amounts of gravitational radiation produced in the interaction of photons with the static electromagnetic fields of some astrophysical objects. These are the Sun, Quasar 3C273, Seyfert galaxies NGC 1068 and NGC 4151, the Galactic Center, and neutron stars.

scholarly journals Velocity Offsets Due to Mass Outflows in Active Galaxies

2009 ◽  
Vol 5 (S267) ◽  
pp. 387-392
Author(s):  
D. M. Crenshaw ◽  
S. B. Kraemer ◽  
H. R. Schmitt ◽  
R. F. Mushotzky ◽  
J. P. Dunn
Keyword(s):  
Seyfert Galaxies ◽  
Emission Lines ◽  
Host Galaxy ◽  
Host Galaxies ◽  
Ionized Gas ◽  
Ngc 4151 ◽  
Spatially Resolved ◽  
Mass Outflow ◽  
Ngc 1068 ◽  
Narrow Emission

AbstractWe present a study of the radial velocity offsets between AGN-related narrow emission lines and host-galaxy emission and absorption lines in Seyfert galaxies with observed redshifts less than 0.043. We find that 35% of the Seyferts in the sample show [O iii] emission lines with blueshifts with respect to their host galaxies exceeding 50 km s−1, whereas only 6% show redshifts this large, in qualitative agreement with most previous studies. We also find that a greater percentage of Seyfert 1 galaxies show blueshifts than Seyfert 2 galaxies. Using HST/STIS spatially-resolved spectra of the Seyfert 2 galaxy NGC 1068 and the Seyfert 1 galaxy NGC 4151, we generate geometric models of their narrow-line regions (NLRs) and inner galactic disks and show how these models can explain the blueshifted [O iii] emission lines in collapsed STIS spectra of these two Seyferts. We conclude that the combination of mass outflow of ionized gas in the NLR and extinction by dust in the inner disk (primarily in the form of dust spirals) is primarily responsible for the velocity offsets in Seyfert galaxies.

scholarly journals Optical Variability of the Nuclei of Seyfert Galaxies

1975 ◽  
Vol 67 ◽  
pp. 591-604
Author(s):  
V. M. Lyuty ◽  
V. I. Pronik
Keyword(s):  
Seyfert Galaxies ◽  
Emission Lines ◽  
Optical Variability ◽  
Central Source ◽  
The Continuum

The continuum variability (UBV observations), the variations in the emission lines, and the properties of the central source in the nuclei of Seyfert galaxies are discussed. There is the quasi-periodicity in the light variations of the nuclei. The emission lines show the variations both in the intensity and the profiles. All data lead to the conclusion, that both continuum and emission-lines intensity variations are due to the variability of the central nonthermal source.

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.

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