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

A linear correlation has been proposed between the CO luminosity (L-CO') and the full width at half-maximum (FWHM) for high-redshift (z > 1) submillimetre galaxies. However, the controversy concerning the L-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 L-CO'-FWIIM correlations for both low-redshift and high-redshift samples. A comparison of the low- and high-redshift L-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 omega CDM with our samples, the derived values are omega(0) = -1.02 +/- 0.17, Omega(m0) = 0.30 +/- 0.02 and H-0 = 70.00 +/- 0.60 km s(-1) Mpc(-1).