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Session 78 - Seyfert Galaxies.
Display session, Friday, January 09
Exhibit Hall,
Although the host galaxies of active galactic nuclei(AGN) contain enough interstellar medium to act as the fuel for the AGN, it is not clear how this gas can lose enough angular momentum to be transported down to the central engine. One possibility is that either nested gaseous bars or central bars torque the gas depriving it of angular momentum and thus driving it inward. If so, these central gaseous bars could provide the necessary torque to deprive the ISM of its angular momentum. Until the advent of NICMOS on the HST the lack of resolution and the high amounts of dust in the central regions of the host galaxies prevented these theories from being tested. We present HST NICMOS observations of the central regions of a sample of Seyfert and control galaxies. By combining the 1.6\micron NICMOS images with WFPC2 images we are able to make color maps that probe the dust morphology of the central regions of Seyfert galaxies at unprecedented resolution. The Seyfert galaxies do not show signs of gaseous bars but a large fraction do show an inner spiral structure. Rather than a grand-design two-armed pattern, this spiral structure is, in general, multi-armed or flocculent. These observations show that bars are unlikely to be the method by which gas loses angular momentum but that spiral structure and/or density waves need to be investigated as possible methods for driving gas into the central regions of galaxies.
