Lyα Intensity Mapping in HETDEX: Galaxy-Lyα Intensity Cross-power Spectrum

Abstract

We present a measurement of the Lyα intensity-mapping power spectrum from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). We measure the cross-power spectrum of Lyα intensity and Lyα-emitting galaxies over 1.9 ≤ z ≤ 3.5. The intensity is calculated from HETDEX spectra that do not contain detected Lyα emitters above a signal-to-noise ratio of 5.5. To produce a power-spectrum model and covariance matrix, we simulate the data using lognormal mocks for the emitter catalog and Lyα intensity in redshift space, including the HETDEX sensitivity, selection function, and mask. In three redshift bins centered at z = 2.1, 2.6, and 3.2, the measurements yield amplitudes of (6.7 ± 3.1), (11.7 ± 1.4), and (8.3 ± 1.5) × 10⁻²² erg s⁻¹ cm⁻² arcsec⁻² Å⁻¹, respectively. The results are reasonably consistent with cosmological hydrodynamical simulations that include Lyα radiative transfer, but significantly smaller than previous results from cross-correlations of quasars with Lyα intensity. These results demonstrate the statistical power of HETDEX for Lyα intensity mapping and will help constrain models of Lyα emission from galaxies.