# TARDIS Paper I: A Constrained Reconstruction Approach to Modeling the z~2.5 Cosmic Web Probed by Lyman-alpha Forest Tomography

## TL;DR

TARDIS is a new reconstruction method that accurately infers the initial density field and cosmic web structures at high redshift from Lyman-alpha forest data, outperforming standard techniques and enabling evolution to present-day structures.

## Contribution

The paper introduces TARDIS, a novel constrained reconstruction approach that improves small-scale structure recovery and cosmic web classification from high-redshift Lyman-alpha forest observations.

## Key findings

- TARDIS accurately reconstructs small-scale structures.
- Eigenvalues from TARDIS correlate at r=0.95 with true values.
- Method enables evolution of structures to z=0.

## Abstract

Recent Lyman-$\alpha$ forest tomography measurements of the intergalactic medium (IGM) have revealed a wealth of cosmic structures at high redshift ($z\sim 2.5$). In this work, we present the Tomographic Absorption Reconstruction and Density Inference Scheme (TARDIS), a new chrono-cosmographic analysis tool for understanding the formation and evolution of these observed structures. We use maximum likelihood techniques with a fast non-linear gravitational model to reconstruct the initial density field of the observed regions. We find that TARDIS allows accurate reconstruction of smaller scale structures than standard Wiener filtering techniques. Applying this technique to mock Lyman-$\alpha$ forest data sets that simulate ongoing and future surveys such as CLAMATO, Subaru-PFS or the ELTs, we are able to infer the underlying matter density field at observed redshift and classify the cosmic web structures. We find good agreement with the underlying truth both in the characteristic eigenvalues and eigenvectors of the pseudo-deformation tensor, with the eigenvalues inferred from 30m-class telescopes correlated at $r=0.95$ relative to the truth. As an output of this method, we are able to further evolve the inferred structures to late time ($z=0$), and also track the trajectories of coeval $z=2.5$ galaxies to their $z=0$ cosmic web environments.