# CO luminosity-Linewidth correlation of low and high redshift galaxies and its possible cosmological utilization

## TL;DR

This study confirms a consistent CO luminosity-linewidth correlation across low and high redshifts, enabling its use as a cosmological distance indicator and constraining cosmological parameters.

## Contribution

It provides the first extensive analysis of CO(1-0) data across redshifts, establishing a stable luminosity-linewidth relation for cosmological applications.

## Key findings

- Significant CO luminosity-linewidth correlations found at both redshifts.
- No strong evolution of the correlation with redshift.
- Cosmological parameters constrained using CO data and supernovae.

## Abstract

A linear correlation has been proposed between the CO luminosity ($\rm{L}^{\prime}_{\rm{CO}}$) and full-width at half maximum (FWHM) for high-redshift (z > 1) submillimeter galaxies. However, the controversy concerning the $\rm{L}^{\prime}_{\rm{CO}}$-FWHM correlation seems to have been caused by the use of heterogeneous samples (e.g., different transition lines) and/or data with large measurement uncertainties. In order to avoid the uncertainty caused by using different rotational transitions, in this work we make an extensive effort to select only CO($J = 1-0$) data from the literature. We separate these wide-ranging redshift data into two samples : the low-redshift (z < 1) and high-redshift (z > 1) samples. The samples are corrected for lensing magnification factors if gravitational-lensing effects appeared in the observations. The correlation analysis shows that there exists significant $\rm{L}^{\prime}_{\rm{CO}}$-FWHM correlations for both the low-redshift and high-redshift samples. A comparison of the low- and high-redshift $\rm{L}^{\prime}_{\rm{CO}}$-FWHM correlations does not show strong evolution with redshift. Assuming that there is no evolution, we can use this relation to determine the model independent distances of high-redshift galaxies. We then constrain cosmological models with the calibrated high-redshift CO data and the sample of Type Ia supernovae in the Union 2.1 compilation. In the constraint for wCDM with our samples, the derived values are w_{0} = -1.02 {\pm} 0.17, {\Omega}_{m0} = 0.30{\pm}0.02, and H_{0} = 70.00 {\pm}0.60 km\,s^{-1}\,Mpc^{-1}.