High Spatial Resolution Mid-Infrared Observations of Three Seyfert Galaxies
Images at 12.5 μm of nuclei of three nearby Seyfert galaxies—NGC 1275, NGC 4151, and NGC 7469—have been obtained with the 10 m Keck Telescope. NGC 7469 is resolved and deconvolution delineates a structure (<0farcs04) × 0farcs08, or less than 13 × 26 pc at a position angle of 135°. From a comparison with structure seen at millimeter wavelengths, this structure is interpreted as a disk aligned with the molecular gas in the central few hundred parsecs of the galaxy. NGC 1275 and NGC 4151 are not resolved; limits on the sizes of these nuclei are 0farcs08 and 0farcs16, corresponding to physical spatial scales of 28 and 10 pc. The lower limits to the brightness temperatures implied by these size limits and the measured flux densities are within ~50 K of the 12–25 μm color temperatures of these systems, as inferred from IRAS observations. The angular size limits are within a factor of 2 of the sizes required to spatially resolve thermal emission from dust heated by a central luminosity source. These sizes preclude significant contributions to the nuclear infrared emission from star-forming regions.
Additional Information© 2003. The American Astronomical Society. Received 2003 January 27. Accepted 2003 April 1. We thank the staff of the Keck Observatory for their assistance in making these observations possible. The W. M. Keck Observatory is operated as a scientific partnership between the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. It was made possible by the generous financial support of the W. M. Keck Foundation. We extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, none of the observations presented herein would have been possible. We thank Carol Lonsdale for supplying the VLBI image of NGC 7469. B. T. S. and E. E. were supported by grants from the NSF and NASA. B. T. S. and L. A. are supported by the SIRTF Science Center at Caltech. SIRTF is carried out at JPL, operated by Caltech under an agreement with NASA.
Published - Soifer_2003_AJ_126_143.pdf
Accepted Version - 0304105.pdf