Validation of the DESI 2024 Lyman Alpha Forest BAL Masking Strategy

Understand

Broad absorption line quasars (BALs) exhibit blueshifted absorption relative to a number of their prominent broad emission features.

• These absorption features can contribute to quasar redshift errors and add absorption to the Lyman-alpha (LyA) forest that is unrelated to large-scale structure.
• We present a detailed analysis of the impact of BALs on the Baryon Acoustic Oscillation (BAO) results with the LyA forest from the first year of data from the Dark Energy Spectroscopic Instrument (DESI).
• The baseline strategy for the first year analysis is to mask all pixels associated with all BAL absorption features that fall within the wavelength region used to measure the forest.