Infrared spectroscopy of Seyfert 2 galaxies: A look through the obscuring torus .2.

High-resolution J-band and K-band spectra of a sample of 33 Seyfert 2 galaxies are presented. Two of these galaxies were also observed in the L band. These data are used to look for broad Pa beta, Br gamma, and Br alpha lines, in search of broad-line regions (BLRs) that are hidden by dust at optical wavelengths. Obscured BLRs are confirmed for three previously reported discoveries, and the new data suggest possible BLR detections in as many as six additional Seyfert 2's. Our results are consistent with the standard torus model if the transition zone located between the optically thin ''throat'' of the torus and the optically thick core is rather extended. The dusty wind model of Konigl & Kartje can also explain the data. Comparisons of the broad-line and narrow-line extinctions indicate that the BLRs are considerably more obscured than the narrow-line regions (NLRs). This result agrees with the predictions of both the torus and dusty wind models, where the dust is located between the NLR and the BLR. Comparisons of the column depths to the BLRs with the column depths determined from X-ray data show a general tendency for the objects with detected broad recombination lines to have lower X-ray columns. A large scatter exists between the infrared and X-ray columns depths, however. Fluctuations in the properties of the nuclear gas (e.g., metallicity or gas-to-dust ratio) or differences in the distributions of the ionized and neutral gas components can easily account for this scatter. The widths of broad Pa beta and Br gamma lie on the narrow end of the distribution for Seyfert 1 galaxies. The dereddened broad H beta luminosities predicted from the broad infrared lines are similar to the broad H beta luminosities of normal Seyfert l's, and so are the ratios of the hard X-ray flux to the predicted broad H alpha flux. In objects with a BLR detected through both infrared spectroscopy and spectropolarimetry, the broad infrared lines often are an order of magnitude stronger than the values expected from the scattered flux. The infrared spectra were also used to assess the origin of the [Fe II] and H-2 emission in Seyfert 2 galaxies. The present data rule out the possibility that the [Fe II] emission is produced solely from a circumnuclear starburst. Shocks associated with nuclear outflows are a likely source of both [Fe II] and H-2, although photoionization by the nuclear continuum may also contribute to the [Fe II] emission, and X-ray heating may play a role in producing the H-2 emission.