Cosmological Constraints using the newest VLT-KMOS HII Galaxies and the full Planck CMB spectrum

TL;DR

This study combines HII galaxy data with Planck CMB and BAO measurements to constrain cosmological models, extending the redshift range and confirming consistency with the standard Lambda-CDM model.

Contribution

It introduces a joint analysis of HII galaxies with CMB and BAO data, providing independent cosmological constraints at higher redshifts than supernovae.

Findings

Results agree with Lambda-CDM within 1 sigma.

HII galaxies probe earlier cosmic times than SNIa.

Constraints on dark energy equation of state are consistent with CPL model.

Abstract

We present novel cosmological constraints based on a joint analysis of our HII galaxies (HIIG) Hubble relation with the full Planck Cosmic Microwave Background anisotropy spectrum and the Baryon Acoustic Oscillations (BAO) probes. The HII galaxies span a large redshift range $(0.088 \le z \le 2.5)$, reaching significantly higher redshifts than available SNIa and hence they probe the cosmic expansion at earlier times. Our independent constraints compare well with those based on the Pantheon compilation of SNIa data, which we also analyse. We find our results to be in agreement with the conformal $\Lambda$CDM model within 1$\sigma$. We also use our HIIG data to examine the behaviour of the dark energy equation of state parameter under the CPL parameterisation, $w = w_0+w_a \frac{z}{1+z}$, and find consistent results with those based on SNIa, although the degeneracy in the parameter space as well as the individual parameter uncertainties, when marginalizing one over the other, are quite large.