HETDEX Public Source Catalog 1 -- Stacking 50K Lyman Alpha Emitters

TL;DR

This paper analyzes the ensemble properties of 50,000 Lyman Alpha Emitters from the HETDEX survey by stacking their spectra, revealing average spectral features and physical characteristics of typical high-redshift star-forming galaxies.

Contribution

It presents the first large-scale spectral stacking analysis of 50,000 LAEs, providing detailed average properties and insights into their stellar populations and ionizing radiation leakage.

Findings

Average LAE at z~2.6 is a blue, moderately bright star-forming galaxy.

Stacked spectra reveal strong Lyα emission and potential ionizing photon escape.

Young, metal-poor stellar populations dominate the UV light.

Abstract

We describe the ensemble properties of the $1.9 < z < 3.5$ Lyman Alpha Emitters (LAEs) found in the HETDEX survey's first public data release, HETDEX Public Source Catalog 1 (Mentuch Cooper et al. 2023). Stacking the low-resolution ($R \sim$ 800) spectra greatly increases the signal-to-noise ratio, revealing spectral features otherwise hidden by noise, and we show that the stacked spectrum is representative of an average member of the set. The flux limited, Ly$\alpha$ signal-to-noise ratio restricted stack of 50K HETDEX LAEs shows the ensemble biweight ``average" $z \sim 2.6$ LAE to be a blue (UV continuum slope $\sim -2.4$ and E(B-V) $< 0.1$), moderately bright (M$_{\text{UV}} \sim -19.7$) star forming galaxy with strong Ly$\alpha$ emission (log $L_{Ly\alpha}$ $\sim$ 42.8 and $W_{\lambda}$(Ly$\alpha$) $\sim$ 114\AA), and potentially significant leakage of ionizing radiation. The restframe UV light is dominated by a young, metal poor stellar population with an average age 5-15 Myr and metallicity of 0.2-0.3 Z$_{\odot}$.