Geometrical tests of cosmological models. I. Probing dark energy using the kinematics of high-redshift galaxies

TL;DR

This paper proposes a novel method using high-redshift galaxy rotation speeds as standard rods to measure dark energy parameters through the angular-diameter test, accounting for potential systematic effects.

Contribution

It introduces a new strategy combining spectroscopy and imaging to constrain dark energy and addresses how to diagnose and minimize biases from galaxy evolution.

Findings

High-resolution spectroscopy and imaging can effectively measure dark energy density.

Galaxy disc evolution up to 30% at z=1.5 can be diagnosed and minimally bias results.

A cosmology-evolution diagram links galaxy evolution with different cosmological models.

Abstract

We suggest to use the observationally measured and theoretically justified correlation between size and rotational velocity of galactic discs as a viable method to select a set of high redshift standard rods which may be used to explore the dark energy content of the universe via the classical angular-diameter test. Here we explore a new strategy for an optimal implementation of this test. We propose to use the rotation speed of high redshift galaxies as a standard size indicator and show how high resolution multi-object spectroscopy and ACS/HST high quality spatial images, may be combined to measure the amplitude of the dark energy density parameter, or to constrain the cosmic equation of state parameter for a smooth dark energy component. We evaluate how systematics may affect the proposed tests, and find that a linear standard rod evolution, causing galaxy dimensions to be up to 30% smaller at z=1.5, can be uniquely diagnosed, and will minimally bias the confidence level contours in the [Omega_Q, w] plane. Finally, we show how to derive, without a priori knowing the specific functional form of disc evolution, a cosmology-evolution diagram with which it is possible to establish a mapping between different cosmological models and the amount of galaxy disc/luminosity evolution expected at a given redshift.