Dynamical Dark Energy Imprints in the Lyman-Alpha Forest

TL;DR

This paper investigates how dynamical dark energy models influence the Lyman-Alpha forest, revealing distinct spectral and thermal signatures that could serve as independent observational tests for dark energy's nature.

Contribution

It introduces the first detailed analysis of the impact of dynamical dark energy on the Lyman-Alpha forest using cosmological hydrodynamical simulations.

Findings

DDE models cause a spectral tilt in the transmitted flux power spectrum.

DDE models result in higher intergalactic medium temperatures.

DDE models show reduced Lyman-Alpha opacity compared to Lambda-CDM.

Abstract

The nature of dark energy (DE) remains elusive, even though it constitutes the dominant energy-density component of the Universe and drives the late-time acceleration of cosmic expansion. By combining measurements of the expansion history from baryon acoustic oscillations, supernova surveys, and cosmic microwave background data, the Dark Energy Spectroscopic Instrument (DESI) Collaboration has inferred that the DE equation of state may evolve over time. The profound implications of a time-variable, ``dynamical" DE (DDE) that departs from a cosmological constant motivate the need for independent observational tests. In this work, we use cosmological hydrodynamical simulations of structure formation to investigate how DDE affects the properties of the Lyman-Alpha ``forest'' of absorption features produced by neutral hydrogen in the cosmic web. We find that DDE models consistent with the DESI constraints induce a spectral tilt in the forest transmitted flux power spectrum, imprinting a scale- and redshift-dependent signature relative to standard Lambda-CDM cosmologies. These models also yield higher intergalactic medium temperatures and reduced Lyman-Alpha opacity compared to Lambda-CDM. We discuss the observational implications of these trends as potential avenues for independent confirmation of DDE.