Large-scale Stellar Bars and Nuclear Activity in Narrow-line Seyfert 1 Galaxies

Abstract We present a statistical comparison between barred and unbarred narrow-line Seyfert 1 galaxies (NLS1s) to investigate the role of large-scale stellar bars in fueling active galactic nuclei (AGNs) with low-mass black holes. From a parent sample of 492 NLS1s selected from the Sloan Digital Sky Survey and Pan-STARRS1 (PS1), we construct a PS1-resolved matched sample of 101 barred and 101 unbarred NLS1s, matched in redshift, inclination, and image quality. Unbarred NLS1s are modestly but consistently brighter than barred NLS1s in several optical AGN luminosity indicators, including λL λ (5100 Å), broad H α , broad H β , narrow H α , narrow H β , and [O iii ] λ 5007, with typical offsets of ∼0.1–0.25 dex; the broad H α and narrow-line offsets are statistically significant, while the continuum and broad H β offsets are marginal. Monte Carlo resampling and a Bayesian model support the same direction of offset. In contrast, the main narrow-line diagnostics, including [O iii ]/H β , O3N2, and the [S ii ]-based electron density, are statistically consistent between the subsamples, although barred NLS1s show a higher N2 ratio. Within the barred subsample, the bar strength parameter e max shows a mild anticorrelation with the optical continuum and broad Balmer-line luminosities. These results indicate that large-scale stellar bars are not associated with enhanced instantaneous optical AGN luminosity. Instead, barred systems may experience more regulated or time-variable inner gas delivery, building circumnuclear gas reservoirs without necessarily increasing accretion power observed at the epoch traced by optical AGN emission.