ITAL]Hubble Space Telescope[/ITAL] Imaging of the Central 1 Kiloparsec of M81

Abstract

M81 is the closest example of a galaxy that exhibits both LINER and Seyfert 1 characteristics. New, postrepair (cycle 5), Hubble Space Telescope imaging observations of the central kpc of M81 are presented, specifically, WFPC2 Hα and continuum images, a WFPC2 UV continuum (1500 A) image, and a V-band faint object camera (FOC) image. The continuum image shows a number of sinuous dust lanes that wind into the nucleus of M81. The Hα image reveals a small, ~7'' (120 pc), bright, elliptical region of emission that appears to be a nuclear disk. The center of the disklike structure is offset by less than 06 (10 pc) from the bright unresolved nucleus. The WFPC2 UV image shows that the disk is not ionized by massive stars. The highest angular resolution observations, obtained with the FOC, allow an upper limit of 004 (0.7 pc) to be placed on the size of the nucleus in the V band. The FOC image also shows that there are no stars, star clusters, or additional nuclei visible within the central 4'' × 4'' region of M81 that are brighter than the galaxy background light.