Are “Changing-look” Active Galactic Nuclei Special in the Coevolution of Supermassive Black Holes and their Hosts? II. The Case of Changing-look Narrow-line Seyfert 1 Galaxies

Abstract The evolutionary role of the so-called “changing-look” (CL) active galactic nucleus (AGN), which is characterized by spectral-type transitions within ∼10 yr, has been suggested in the past few years. By focusing on CL-AGNs having spectra similar to those of broad-line Seyfert 1 galaxies, some authors have proposed that CL-AGNs tend to be at a special evolutionary stage associated with intermediate-to-old stellar populations. Here we attempt to verify this evolutionary role by extending the sample to CL narrow-line Seyfert 1 (NLS1) galaxies, which are believed to be “young” AGNs with a less massive supermassive black hole and high accretion rate. Combining the recent large NLS1 catalog provided by V. S. Paliya et al. and the fifth Sloan Digital Sky Survey (SDSS-V) DR19 spectral survey returns only three CL-NLS1s out of a parent sample of 884 objects, reinforcing the rarity of CL-NLS1s. Subsequent spectral analysis shows that the evolutionary role mentioned above still holds, although CL-NLS1s tend to occupy the young end of the intermediate-old population. Finally, we propose that off-center SDSS spectra caused by the “fiber drop” effect have great potential for determining the properties of the narrow-line region of NLS1s.