A new path to constrain the expansion history of the Universe in future spectroscopic galaxy surveys

TL;DR

This paper explores how future spectroscopic galaxy surveys can improve measurements of the Universe's expansion rate using cosmic chronometers, potentially resolving current tensions in cosmology.

Contribution

It proposes that next-generation spectroscopic facilities can significantly enhance the precision of cosmic chronometer measurements, offering model-independent constraints on the expansion history.

Findings

Potential to reduce $H(z)$ measurement uncertainties below 10%

Improved constraints on cosmological parameters like $H_0$ and dark energy properties

Enhanced ability to address the Hubble tension

Abstract

The current tension between early- and late-Universe measurements of the Hubble constant ($H_0$), along with the still elusive nature of dark matter and dark energy, calls for model-independent probes of the Universe's expansion history. The cosmic chronometers (CC) method offers a unique opportunity to directly measure the Hubble parameter $H(z)$ without relying on any cosmological model assumptions or integrated distance measurements. Despite its potential, this technique remains statistics-limited: no current survey is optimized to detect large samples of CC, restricting the precision on $H(z)$ to $\sim$20% at intermediate redshifts. Here, we investigate the opportunities that a next-generation spectroscopic facility could offer to CC studies, providing an estimate of the accuracy achievable on the reconstruction of the Hubble parameter in redshift. We demonstrate that with such a facility, it will be possible to derive constraints on key cosmological parameters, assessing the impact that such improvements would have on our understanding of the expansion history of the Universe and on current cosmological tensions.