High-redshift Narrow-line Seyfert 1 Galaxies: A Candidate Sample

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$\beta$ 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$\beta$ and Mg II lines of a large sample of SDSS DR14 quasars to find high-$z$ NLS1 candidates. Based on the strong correlation of $\mathrm{FWHM}(\mathrm{MgII})=(0.880\pm 0.005)\times \mathrm{FWHM}(\mathrm{H}\beta )+(0.438\pm 0.018)$, 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 $46.16\pm 0.42$ erg s${}^{-1}$, logarithmic black hole mass of $8.01\pm 0.35M_{\odot }$, and logarithmic Eddington ratio of $0.02\pm 0.27$. 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.

Published in ApJS on March 2021. Catalog is available on Zenodo (https://doi.org/10.5281/zenodo.4405039)

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