A Catalog of Spectral Properties for DESI DR1 Quasars

The Dark Energy Spectroscopic Instrument (DESI) is carrying out a five-year spectroscopic survey designed to map the large-scale structure of the Universe and obtain spectra for millions of galaxies and quasars over a wide redshift range. We present a value-added catalog of spectral properties for 1,717,774 unique quasars (1,774,723 spectra) in the DESI Data Release 1. We perform a uniform spectral decomposition of the quasar continuum, host galaxy emission (at $z<1$), and \FeII\ emission, and measure the line properties of major broad and narrow emission lines from Ly$\alpha$ to H$\alpha$ covered by DESI spectra. We also provide single-epoch black hole mass estimates (from H$\beta$, \MgII, and \CIV), bolometric luminosities, and Eddington ratios for these quasars. We provide systemic redshifts that account for the intrinsic velocity shifts of individual lines; they agree with the DESI pipeline redshifts to within 500~km s${}^{-1}$ for 88.6% of the sample, and are most useful at $z>1$ where the pipeline redshift is heavily constrained by blueshifted high-ionization lines. We also provide local fits to several optical coronal lines, including \NeV~$\lambda 3426$, [\ion{Fe}{7}]~$\lambda 5722$, [\ion{Fe}{7}]~$\lambda 6088$, and [\ion{Fe}{11}]~$\lambda 7893$. We show that several emission-line ratios, including those involving coronal lines, vary systematically with Eddington ratio. The catalog is intended as a community resource for studies of quasar demographics, black hole accretion, emission-line physics, and the connection between the broad-, coronal-, and narrow-line regions.