AAS Meeting #193 - Austin, Texas, January 1999
Session 90. Ultra-Luminous IR Galaxies/AGN - The Central Regions
Oral, Friday, January 8, 1999, 2:00-3:30pm, Room 8 (A,B,C)

[Previous] | [Session 90] | [Next]

[90.04D] Speckle Imaging of the Nuclei of Six Seyfert Galaxies at Wavelengths of 2.2 \mum and 1.6 \mum

A. J. Weinberger (UCLA), G. Neugebauer, K. Matthews (Caltech)

Six Seyfert galaxies were observed with speckle imaging techniques in the near-infrared H-band (1.6 \mum) and K-band (2.2 \mum). Observations of all the sources, NGC 1068, MRK 231, NGC 3227, NGC 4151, NGC 5506, and NGC 7469, were made at the Palomar 200-inch Telescope and K-band observations of NGC 1068 were also made with the 10-m W. M. Keck Telescope. Diffraction limited or near-diffraction limited resolutions of 0.''05 - 0.''15 were obtained.

Images of the nucleus of NGC 1068 reveal an extended region of emission which accounts for nearly 50% of the nuclear flux at K-band. This region extends 10 pc on either side of an unresolved point source. Both the point source and the newly revealed extended emission are very red, with identical H-K colors. The extended region must be composed of either nuclear emission which has been reflected off an extended dusty disk or of small grains raised to transiently high temperatures by reflected UV photons.

Images of the nuclear region of the Seyfert 1.5 galaxy NGC 3227 also show an unresolved point source as well as an extended region. In H-K color, however, the nucleus is much redder than the extended source and is consistent with emission from grains in thermal equilibrium with the central luminosity source. The bluer extended source is likely to be a continuation of the known bright central stellar cluster. Extended Ls-band emission imaged at 70-250 pc from the nucleus is also likely to arise from stars.

Speckle measurements of the other four galaxies are used to place upper limits on the sizes of their unresolved cores. In each, the size of the nuclear emission is consistent with near-infrared flux emitted from grains in thermal equilibrium with the central luminosity source.

[Previous] | [Session 90] | [Next]