A Catalog of Narrow Line Seyfert 1 Galaxies from the Sloan Digital Sky Survey Data Release 12

We present a new catalog of narrow-line Seyfert 1 (NLSy1) galaxies from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12). This was obtained by a systematic analysis through modeling of the continuum and emission lines of the spectra of all the 68,859 SDSS DR12 objects that are classified as “QSO” by the SDSS spectroscopic pipeline with z< 0.8 and a median signal-to-noise ratio (S/N) > 2 pixel^-1. This catalog contains a total of 11,101 objects, which is about 5 times larger than the previously known NLSy1 galaxies. Their monochromatic continuum luminosity at 5100 Å is found to be strongly correlated with Hβ, Hα, and [O III] emission line luminosities. The optical Fe II strength in NLSy1 galaxies is about two times larger than the broad-line Seyfert 1 (BLSy1) galaxies. About 5% of the catalog sources are detected in the FIRST survey. The Eddington ratio ({ξ }_{Edd}) of NLSy1 galaxies has an average of {log} {ξ }_{Edd} of -0.34, much higher than -1.03 found for BLSy1 galaxies. Their black hole masses ({M}_{BH}) have an average of {log} {M}_{BH} of 6.9 {M}_⊙ , which is less than BLSy1 galaxies, which have an average of {log} {M}_{BH} of 8.0 {M}_⊙ . The {M}_{BH} of NLSy1 galaxies is found to be correlated with their host galaxy velocity dispersion. Our analysis suggests that geometrical effects playing an important role in defining NLSy1 galaxies and their {M}_{BH} deficit is perhaps due to their lower inclination compared to BLSy1 galaxies.