Discovery of four Narrow-line Type-1 Quasars at z = 2.54 -- 6.06 with Subaru 'Onohi'ula PFS-SSP

The team searched for broad-line AGNs whose rest-UV spectra resemble local narrow-line Seyfert 1 (NLS1) galaxies, using the Lyα line profile as a selection tool. They identified four NLQ1s, including one candidate, at z = 2.54–6.06, each showing a prominent Lyα emission line with very low continuum.

The measured Lyα FWHM ranges from 1410 to 1510 km/s (mean ~1430 km/s), and the rest-frame equivalent widths are high (mean ~190 Å), exceeding typical quasar values. Two objects have exceptionally large Lyα luminosities, accounting for 3–4% of bolometric luminosity.

For three objects with C IV line measurements, black hole masses are ~10^6.9–10^7.7 solar masses, with Eddington ratios > 0.1, consistent with low-redshift NLS1 galaxies. One quasar shows N V and C IV broad absorption lines, classifying it as a mini-BAL quasar and supporting the interpretation that this NLQ1 is a luminous version of an NLS1 galaxy.