Lyα Nebulae in HETDEX: The Largest Statistical Census Bridging Lyα Halos and Blobs across Cosmic Noon

Abstract

The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is an untargeted approximately 540 deg² spectroscopic survey of Lyα emission at 1.9 < z < 3.5. We select 70,691 Lyα-emitting galaxies with emission-line signal-to-noise ratios greater than 6 and model their Lyα emission as a point-source component with an optional exponential envelope. Approximately 47.5% of the sample, or 33,612 objects, exhibits significant extended emission and is best fit by the two-component model. The fraction of resolved sources increases with Lyα flux and luminosity. Their isophotal areas range from 10 to 130 arcsec², with integrated Lyα fluxes from 6 to 2000 × 10⁻¹⁷ erg s⁻¹ cm⁻². Comparison between point-spread-function-weighted and isophotal flux measurements shows that the HETDEX pipeline underestimates total Lyα flux by approximately 30% on average, reflecting the substantial halo contribution. Approximately 420 Lyα nebulae are found per deg² over 79.5 deg² of noncontiguous sky. We present a catalog of more than 70,000 modeled sources, including approximately 33,000 spatially extended nebulae, with positions, redshifts, luminosities, and structural parameters.