An Investigation of Co Luminosity-Linewidth Correlation Among Low and Highz Galaxies and Its Possible Cosmological Utilization
Y. H. Wu1*, Goto, Tomotsugu1
1Institute of Astronomy, National Tsing Hua University, HsinChu, Taiwan
* presenting author:Y. H. Wu,
The evolution of dark energy has been a big issue in cosmology. The distance measurement of bright, luminous objects at high z regions can provide the clue of the evolution in the further cosmological constrains.

Galaxies with CO detection can be a reliable tool since the observation can reach to high z
range and the empirical relation between CO luminosity (L`CO) and the linewidth (FWHM) has been proposed. The goal of this study is to investigate if L`CO-FWHM correlation evolves with respect to z. We compiled published CO data only in 1-0 transition from the literature, both at low and high z, to avoid the uncertainty caused by different transitions. Lambda CDM model was adopted in deriving the luminosity distances of the samples. After the considerations of line width correction and mu (magnificent factor) correction, we separately established L`CO-FWHM correlations in the low and high z samples for comparison. We found that both
corrections reduce the scatter of the data along the linear regressions and the two correlations were consistent within the statistical error.

Additionally, to investigate a potential of using CO galaxies as distance indicators, we used 580 Type Ia supernovae (0.015 < z < 1.414) in the Union 2.1 as the distance calibrators for the low-z
sample (z < 1) and then established a calibrated low-z L`CO-FWHM correlation to estimate the cosmology-independent distances for the high-z sample, following our finding of no significant evolution in the L`CO-FWHM correlation. We compared the previous datasets (SNe Ia and GRB) with our estimated data on the Hubble Diagram. Although the error is significant, our high-z sample is consistent with the concordance LCDM model. Thus, we conclude that CO galaxies may be possible to be distance indicators.

Keywords: Cosmology