Indecent Exposure in Seyfert 2 Galaxies: A Close Look

TL;DR

This study investigates Seyfert 2 galaxies that show signs of being unobscured and lack broad emission lines, challenging the traditional AGN unification model by suggesting some are intrinsically naked active nuclei.

Contribution

It provides evidence that certain Seyfert 2 galaxies are intrinsically devoid of broad-line regions, contrary to the expectation of obscuration in the unification model.

Findings

No broad emission lines detected in optical and near-infrared spectra.

These galaxies are likely unobscured, intrinsically naked AGNs.

Challenges the standard AGN unification paradigm.

Abstract

NGC 3147, NGC 4698 and 1ES 1927+654 are active galaxies that are classified as Seyfert 2s, based on the line ratios of strong narrow emission lines in their optical spectra. However, they exhibit rapid X-ray spectral variability and/or little indication of obscuration in X-ray spectral fitting, contrary to expectation from the active galactic nucleus (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 H-alpha and direct broad Pa-beta or Br-gamma emission lines in these objects. We found no evidence for any broad emission lines from the active nucleus of these galaxies, suggesting that they are unobscured, completely "naked" AGNs that intrinsically lack broad-line regions.