Improved Lyα Tomography Using Optimized Reconstruction with Constraints on Absorption (ORCA)

Abstract

Abstract In this work, we propose an improved approach to reconstruct the three-dimensional intergalactic medium from observed Lyα forest absorption features. We present our new method, the Optimized Reconstruction with Constraints on Absorption (ORCA), which outperforms the current baseline Wiener filter (WF) when tested on mock Lyα forest data generated from hydrodynamical simulations. We find that both reconstructed flux errors and cosmic web classification improve substantially with ORCA, equivalent to 30%–40% additional sight lines with the standard WF. We use this method to identify and classify extremal objects, i.e., voids and (proto)clusters, and find improved reconstruction across all summary statistics explored. We apply ORCA to existing Lyα forest data from the COSMOS Lyman Alpha Mapping and Tomography Observations (CLAMATO) Survey and compare it to the WF reconstruction.