The Lack of Broad Line Regions in Unobscured Seyfert 2 Galaxies

NGC 3147, NGC 4698 and 1ES 1927+654 are active galaxies that are classified as Seyfert 2s, based on the line ratios and presence of strong narrow emission lines in their optical spectra. However, they exhibit rapid X-ray spectral variability and/or little indication of obscuration from Chandra spectra, contrary to expectation from the standard AGN unification model. Using optical spectropolarimetry with LRIS and near-infrared spectroscopy with NIRSPEC at the W. M. Keck Observatory, we conducted a deep search for hidden polarized broad Hα and direct broad Paβ or Brγ emission lines in these objects. We found no evidence of any broad emission lines from the active nucleus of NGC 3147, NGC 4698 or 1ES 1927+654. These results provide support to the idea that these AGNs intrinsically lack broad-line regions, and "true" Seyfert 2 galaxies may exist in nature.