2021ApJ...922..167Z

We present Lyα and ultraviolet (UV)-continuum luminosity functions (LFs) of galaxies and active galactic nuclei (AGNs) at z = 2.0-3.5 determined by the untargeted optical spectroscopic survey of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in 11.4 deg² of fiber spectra sky coverage, obtaining 18,320 galaxies spectroscopically identified with Lyα emission, 2126 of which host type 1 AGNs showing broad (FWHM > 1000 km s^–1) Lyα emission lines. We derive the Lyα (UV) LF over 2 orders of magnitude covering bright galaxies and AGNs in logL_Lyα/[ergs^–1]=43.3–45.5 (-27 < M_UV < -20) by the 1/V_max estimator. Our results reveal that the bright-end hump of the Lyα LF is composed of type 1 AGNs. In conjunction with previous spectroscopic results at the faint end, we measure a slope of the best-fit Schechter function to be α_Sch=-1.70_–0.14^+0.13, which indicates that α_Sch steepens from z = 2-3 toward high redshift. Our UV LF agrees well with previous AGN UV LFs and extends to faint-AGN and bright-galaxy regimes. The number fraction of Lyα-emitting objects (X_LAE) increases from M_UV^* ∼-21 to bright magnitude due to the contribution of type 1 AGNs, while previous studies claim that X_Lyα decreases from faint magnitudes to M_UV^* , suggesting a valley in the X_Lyα-magnitude relation at M_UV^* . Comparing our UV LF of type 1 AGNs at z = 2-3 with those at z = 0, we find that the number density of faint (M_UV > -21) type 1 AGNs increases from z ∼ 2 to 0, as opposed to the evolution of bright (M_UV < -21) type 1 AGNs, suggesting AGN downsizing in the rest-frame UV luminosity.