Studies of Extragalactic Nebulae. V. Motions in the Seyfert Galaxy NGC 1068
Abstract
Spectroscopic observations in seven position angles have been obtained with the prime-focus spectro- graph and with the Lallemand electronic camera attached to the focus of the coudé spectrograph of the 120-inch reflector. These spectra reveal the presence in the nucleus of three or four discrete clouds of material with internal turbulent velocities and velocities with respect to the center of up to 600 km/sec The diameters of these clouds are of the order of 200-350 pc, their masses of the order of 10°-~10~ 9J~o, and their characteristic expansion ages of the order of 106_be years. Similar clouds are directly observable or inferred in the Seyfert galaxies NGC 4151 and NGC 7749, and in the elliptical galaxy NGC 4486. The presence of a synchrotron component in the optical-region radiation of the nucleus is suggested by the photoelectric detection of a polarization of 8.8 per cent in ultraviolet light; the polarization in yellow light is «=O.5 per cent. Measurable optical-region polarization was also detected in the nuclei of the Seyfert galaxies NGC 1275, NGC 5548, and NGC 7469, being particularly strong in NGC 1275, which is the radio source 3C 84. Analysis of the velocity curves outside the nucleus indicates that out to a radial distance of r r~~' 25" the motion is a combination of rotation and expansion, while beyond r = 30", only rotation occurs. Thus, the entire central region is disturbed, perhaps as a result of an earlier generation of the type of violent event now observed in the nucleus. Comparison is made with other galaxies showing ejection of material, and the bearing of the discrete nature of the ejection and its probable repetition at intervals of the order of 106 years (and possibly much less) on proposed explanations of the source of the large energy release in the nuclei of Seyfert galaxies and radio sources is discussed
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1968
- DOI:
- 10.1086/149420
- Bibcode:
- 1968ApJ...151...71W