Distance Measurement of Galaxies to 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 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 up to 29,000 km/s using the Nobeyama 45-m mm-wave Telescope, and some supplementary data were obtained by using the IRAM 30-m telescope. We have detected the CO line emission for several galaxies, and used their CO line widths to estimate the absolute luminosities using the line-width-luminosity relation. In order to obtain photometric data and 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, and Hubble ratios were estimated for these galaxies. We propose that the CO line width-luminosity relation can be a powerful method to derive distances of galaxies to redfhift of z = 0.1 and to derive the Hubble ratio in a significant volume of the universe. Key words: Cosmology - Galaxies: general - Distance scale - CO line