Doctor of Philosophy, The Ohio State University, 2023, Physics

Correlations in and with the flux transmission of the Lyman-alpha (LyA) 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 ~0.1c. As these absorption features can both fall in the forest region and be difficult to distinguish from LyA absorption, cosmological analyses eliminate the ~12 - 16% of quasars that exhibit BALs. This work explores an alternate approach that includes BALs in the LyA auto correlation function, with the exception of the expected locations of the BAL absorption troughs. This procedure is tested on both the SDSS DR14 and DESI Year 1 LyA catalogs, using the reduction of error on the autocorrelations as a metric for success. The masking procedure returns over 95% of the pathlength that is lost by the exclusion of BALs, as well as increases the density of sightlines. It shows that including BAL quasars reduces the fractional uncertainty in the covariance matrix and correlation function by 12% on SDSS DR14 and 20% on DESI Year 1. Furthermore, it does not significantly change the shape of the correlation function relative to analyses that exclude BAL quasars. It also evaluates different definitions of BALs, masking strategies, and potential differences in the quasar continuum in the forest region for BALs with different amounts of absorption.

Committee: Paul Martini (Advisor); Linda Carpenter (Committee Member); Chris Hirata (Committee Member); Klaus Honscheid (Advisor) Subjects: Astronomy; Physics