High-redshift Narrow-line Seyfert 1 Galaxies: A Candidate Sample
Suvendu Rakshit, C. S. Stalin, Jari Kotilainen, Jaejin Shin
Abstract
Abstract The study of narrow-line Seyfert 1 galaxies (NLS1s) is now mostly limited to low redshift ( z < 0.8) because their definition requires the presence of the H β emission line, which is redshifted out of the spectral coverage of major ground-based spectroscopic surveys at z > 0.8. We studied the correlation between the properties of H β and Mg ii lines of a large sample of SDSS DR14 quasars to find high- z NLS1 candidates. Based on the strong correlation of FWHM(Mg II ) = (0.880 ± 0.005) × FWHM(H β ) + (0.438 ± 0.018), we present a sample of high- z NLS1 candidates having FWHM of Mg ii < 2000 km s −1 . The high- z sample contains 2684 NLS1s with redshift z = 0.8–2.5 with a median logarithmic bolometric luminosity of 46.16 ± 0.42 erg s −1 , logarithmic black hole mass of 8.01 ± 0.35 M ⊙ , and logarithmic Eddington ratio of 0.02 ± 0.27. The fraction of radio-detected high- z NLS1s is similar to that of the low- z NLS1s and SDSS DR14 quasars at a similar redshift range, and their radio luminosity is found to be strongly correlated with their black hole mass.