Instrumental Effects of Lyα Properties in CLASSY and Implication for HETDEX and JWST

Abstract In this work, we quantify the effects of spectral resolution (R) on the measured Lyα properties and determine the robustness of Lyα trends measured with different spectrographs. We select 9 galaxies with diverse Lyα properties from the COS Legacy Archive Spectroscopic SurveY and measure the equivalent width and peak velocities of their Lyα profiles from their high-resolution spectra (R ∼ 4225–15000). We downgrade these spectra to several lower resolutions (R ∼ 800–3500) and re-measure the Lyα properties. Using these values, we derive the systematic errors and investigate the robustness of Lyα properties as a function of spectral resolution. We find that equivalent width can be robustly measured at low R. However, the minimal spectral resolution required to obtain robust measurements of the Lyα peak velocities is R ≳ 2600 (Δv = 115 km s−1).