Distance Measurement of Galaxies to a Redshift of ∼ 0.1 Using the CO-Line Tully-Fisher Relation

Abstract

We report on the first results of a long-term project to derive the distances of galaxies at cosmological distances by applying the CO-line width–luminosity relation. We have obtained deep CO-line observations of galaxies at redshifts of up to cz ∼ 29000 km s-1 using the Nobeyama 45-m mm-wave telescope; also, some supplementary data were obtained using the IRAM 30-m telescope. We have detected CO-line emission from several galaxies, and used their CO-line widths to estimate the absolute luminosities based on the line-width–luminosity relation. In order to obtain photometric data and an inclination correction, we also performed optical imaging observations of the CO-detected galaxies using the CFHT 3.6-m telescope at high resolution. The radio and optical data have been combined to derive the distance moduli and distances of the galaxies; also, the Hubble ratios were estimated for these galaxies. We propose that the CO-line width–luminosity relation can be a powerful method to derive the distances of galaxies to redfhifts of z ∼ 0.1, and to derive the Hubble ratio within a significant volume of the universe.