The impact and mitigation of broad absorption line quasars in Lyman$-\alpha$ forest correlations

Understand

Correlations in and with the flux transmission of the Lyman$-\alpha$ (Ly$\alpha$) forest in the spectra of high-redshift quasars are powerful cosmological tools, yet these measurements can be compromised if the intrinsic quasar continuum is significantly uncertain.

• One particularly problematic case is broad absorption line (BAL) quasars, which exhibit blueshifted absorption associated with many spectral features that are consistent with outflows of up to $\sim0.1c$.
• As these absorption features can both fall in the forest region and be difficult to distinguish from Ly$\alpha$ absorption, cosmological analyses eliminate the 12 - 16% of quasars that exhibit BALs.
• In this paper we explore an alternate approach that includes BALs in the Ly$\alpha$ auto correlation function, with the exception of the expected locations of the BAL absorption troughs.