The Extreme Quasar Main Sequence of Super-Eddington DESI-DR1 NLSy1 Galaxies

Abstract: The quasar main sequence, or Eigenvector 1 (EV1), describes the optical diversity of active galactic nuclei (AGN), with Narrow-Line Seyfert 1 (NLSy1) galaxies anchoring the high-accretion end. Recent discoveries of overly massive black holes in the early Universe highlight the need to study local, low-mass super-Eddington accretors as analogs of rapid black hole growth. We map a population of 18,749 NLSy1 galaxies identified in the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1) onto the EV1 plane to determine whether they represent a distinct population of super-accretors. We compare the spectral properties of the DESI DR1 NLSy1 sample with the SDSS DR17 NLSy1 catalog. We extract key parameters, including the broad H-beta full width at half maximum (FWHM) and Fe II strength (R4570). To evaluate their accretion states, we derive single-epoch virial black hole masses using an Fe II strength-dependent scaling relation and an Eddington rate-dependent fundamental plane. The DESI DR1 NLSy1 population shows a shift toward the extreme end of the EV1 parameter space, with stronger Fe II emission (median log R4570 = -0.03) than the SDSS sample (-0.31). Furthermore, the DESI sources host less massive black holes (median log black hole mass ~6.73) than the SDSS objects (6.77-6.91). Given comparable continuum luminosities, a larger fraction of the DESI sample (43.8%-47.7%) exceeds the Eddington limit (log Eddington ratio > 0) than the SDSS sample (20.6%-37.4%). The sensitivity of DESI has unveiled a large population of low-mass, super-Eddington accreting AGN largely missing from previous surveys. These extreme EV1 objects naturally produce the observed intense Fe II emission. This unique sample provides a statistical dataset of local super-Eddington accretors for understanding early-Universe black hole growth.