arXiv:astro-ph/0309083v1 3 Sep 2003 Astrophysical Journal Compact Nuclear Starbursts in Seyfert 2 Galaxies from the CfA and 12µm Samples Masatoshi Imanishi 1,2,3 National Astronomical Observatory, Mitaka, 2-21-1, Osawa, Tokyo 181-8588, Japan imanishi@optik.mtk.nao.ac.jp ABSTRACT We present infrared 2.8–4.1 µm slit spectra of 32 Seyfert 2 galaxies in the CfA and 12 µm samples. The 3.3 µm polycyclic aromatic hydrocarbon (PAH) emission feature was used to estimate the absolute magnitude of a compact nu- clear starburst (less than a few hundred parsecs in size) that is presumed to have occurred in the outer region of an obscuring dusty molecular torus around a central supermassive black hole. We detected 3.3 µm PAH emission in 11 of the 32 Seyfert 2 nuclei in our sample, providing evidence for the presence of compact nuclear starbursts in a significant fraction of Seyfert 2 nuclei. However, the rest-frame equivalent widths of the 3.3 µm PAH emission, and the 3.3 µm PAH-to-infrared luminosity ratios measured in this study suggest that compact nuclear starbursts generally do not contribute significantly to the observed 3–4 µm nuclear fluxes or to the infrared luminosities of Seyfert 2 galaxies. Absorption features at 3.4 µm from bare dust were clearly detected in only two of the nuclei, and features at 3.1 µm from ice-covered dust were detected in only one nucleus. If the dust properties in the direction of these Seyfert 2 nuclei do not differ signifi- cantly from the Galactic interstellar medium, then these small absorption optical 1 Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement no. NCC 5-538 with the National Aeronautics and Space Administration, Office of Space Science, Planetary Astronomy Program. 2 Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. 3 Department of Astronomy, School of Science, Graduate University for Advanced Studies, Mitaka, Tokyo 181-8588