paper

Adaptive optics imaging of the nuclei of Seyfert 2 galaxies: An unexpectedly high incidence of nuclear stellar rings

arXiv:2607.13739 · doi:10.1051/0004-6361/202558474

Abstract

High-resolution imaging of active galactic nuclei (AGNs) on subkiloparsec scales is essential for investigating their fueling. Observations in the near-infrared (NIR) are especially valuable as they minimize the absorption by dust. However, the inferred nuclear morphology may depend on the method used to analyze the images. We assess whether ground-based adaptive-optics observations of the cores of Seyfert 2 galaxies in the Ks band provide advantages over HST observations at shorter wavelengths (V and H bands). We also investigate whether a dedicated 2D analysis is preferable to a 1D approach. A sample of 18 Seyfert 2 galaxies was observed with the adaptive optics (AO) system in the Ks band at the Large Binocular Telescope (LBT) and compared to archival HST V- or H-band images. The analysis included a 2D modeling procedure via GALFIT as well as an unsharp masking technique. Results from different filters are consistent, showing no clear advantage of the redder filter. Using both GALFIT and unsharp masking in tandem is preferable, as the two methods provide complementary strengths. We identified nuclear stellar rings in 8 of the 18 galaxies in our sample (44 +/- 12%). This fraction is significantly higher than reported in previous studies and about a factor of two higher than reported in the most complete atlas of nuclear rings. The radii, size distribution, and inferred masses of the detected nuclear rings are similar to those observed in non-active galaxies. Low-luminosity AGNs appear to have little impact on nuclear ring formation and evolution. The high incidence of nuclear stellar rings in our study is unexpected and warrants further investigation. This could be tested further using the large number of suitable archival HST images available. If confirmed, it would imply that nuclear stellar rings are considerably more common than previously recognized.

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