Comparing Simulations and Observations of the Lyα Forest. I. Methodology

We describe techniques for comparing spectra extracted from cosmologicalsimulations and observational data, using the same methodology to linkLyman-alpha properties derived from the simulations with properties derivedfrom observational data. The eventual goal is to measure the coherence orclustering properties of Lyman-alpha absorbers using observations of quasarpairs and groups. We quantify the systematic underestimate in opacity that isinherent in the continuum fitting process of observed spectra over a range ofresolution and signal-to-noise ratio. We present an automated process fordetecting and selecting absorption features over the range of resolution andsignal-to-noise of typical observational data on the Lyman-alpha "forest".Using these techniques, we detect coherence over transverse scales out to 500h^{-1}_{50} kpc in spectra extracted from a cosmological simulation at z = 2.Comment: 52 pages, includes 14 figures, to appear in ApJ v566 Feb 200