CO luminosity - line width correlation of sub-millimeter galaxies and a possible cosmological application

TL;DR

This study investigates whether a correlation exists between CO luminosity and line width in high-redshift submillimeter galaxies, considering various observational effects, and explores its potential for cosmological distance measurement.

Contribution

The paper provides the first large-sample analysis confirming a weak but significant L_CO-FWHM correlation in submm galaxies, accounting for selection effects and lensing.

Findings

A weak but significant L_CO-FWHM correlation is found.

Selection effects and lensing are crucial in analyzing the relation.

Potential application in cosmological distance measurement is discussed.

Abstract

Context. A possible correlation between CO luminosity (L_CO ) and its line width (FWHM) has been suggested and denied in the literature. Such claims were often based on a small, or heterogeneous sample of galaxies, and thus inconclusive. Aims. We aim to prove or dis-prove the L_CO -FWHM correlation. Methods. We compile a large sample of submm galaxies at z>2 from the literature, and investigate the L_CO-FWHM relation. Results. After carefully evaluating the selection effects and uncertainties such as inclination and magnification via gravitational lensing, we show that there exist a weak but significant correlation between L_CO and FWHM. We also discuss a feasibility to measure the cosmological distance using the correlation.