The Stellar Distribution in the Nuclear Region of the Low-Luminosity Seyfert Galaxy M81

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Session 66 -- Spiral Galaxies
Oral presentation, Thursday, January 13, 2:15-3:45, Salon VI Room (Crystal Gateway)

[66.02] The Stellar Distribution in the Nuclear Region of the Low-Luminosity Seyfert Galaxy M81

G. A. Bower (STScI), A. S. Wilson (STScI/U Md), D. O. Richstone (U. Michigan), T. M. Heckman (STScI/JHU)

We review recent evidence consistent with the presence of a $\approx 10^7 \ M_{\odot}$ black hole in the nucleus of the nearby low-luminosity type 1 Seyfert galaxy M81. Although the nature of the nuclear activity and estimated mass of the central engine have been determined from previous ground-based observations, high resolution images from the Hubble Space Telescope reveal that M81 contains a nuclear structure with similar morphological features as M87. Lauer et al. (1992, AJ, 103, 703) demonstrated that the nuclear structure of M87, which includes a nuclear point source, the optical jet, and a power law stellar distribution, is consistent with the presence of a supermassive black hole. For M81 we compare the analysis of a FOC continuum image (Crane et al. 1993, AJ, 106, 1371) to our analysis of a PC continuum image from the HST archive. Both images show that the central 1$''$ of M81 contains a nuclear point source surrounded by a power law surface brightness profile. Since the FOC and PC images have nearly identical bandpasses, it is not possible to determine the contribution of nonstellar light to the central point source from these images alone. However, nonstellar light may be significant since published observations demonstrate that the nucleus contains an ultracompact ($\sim 1000$ AU) self-absorbed synchrotron radio source and a compact X-ray source.

Spectroscopic observations with HST after the servicing mission have been approved to use the optical absorption lines in the nuclear region to determine the significance of nonstellar light and to map the stellar dynamics.

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