New Tracers for the Evolution of the Dark Energy? an Investigation of the Co(1-0) Luminosity-Linewidth and [Cii] Luminosity-Linewidth Relations
Han Wu1*, Tomotsugu Goto1
1Institute of Astronomy, National Tsing-Hua University, Hsin-Chu, Taiwan
* Presenter:Han Wu, email:starwyh@gmail.com
A correlation between the CO luminosity (L’CO ) and the linewidth of galaxies has been proposed, but yet controversial. To investigate the relation, we compiled only CO(1-0) rotational transition to avoid the uncertainty from conversions between different CO transitions in literature, both at low(z < 1) and high (z > 1) redshifts. Using this larger, more uniform sample, we tested the L’CO(1-0)-linewidth correlation, and examined if it evolves with redshift or not. Inclinations and magnification factors were carefully corrected in order to reduce the scatter in the correlation. After, we independently confirmed the L’CO -FWHM correlations for the low and high z samples. We found that both
correlations are significant in the Spearman‘s coefficients, and these two correlations are consistent to each other, providing no evidence of the redshift evolution.

With the assumption of no evolution, we also demonstrate a possible cosmological use of the correlation. We calibrated the L’CO(1-0)-FWHM relation of the low-z galaxies with the cosmology-independent distances in the literature and estimated the luminosity distances to the 48 high-z (z > 1) CO galaxies. Together with SNIa and GRB samples in the literature, we constrained cosmological parameters and showed that the galaxies which were observed in CO(1-0) can be potentially used as a tracer to probe the evolution of the dark energy.

Additionally, the observations of the [CII] emission can also reach to the distant galaxies in the high-z regions. The strong [CII] emission enables us to investigate the dynamical properties of distant galaxies as in the case of CO(1-0). Hence, in this work, we intend to prove that the galaxies which are observed in [CII] emission have the similar scaling relation as that in CO(1-0) emission, and can be utilized in the cosmological
constraint and probing the evolution of the dark energy.

Another potentially useful emission line is [CII]158um. The [CII] line is generally much brighter than CO lines, and thus, could potentially reach much fainter galaxies, possibly at higher redshifts. We also tested [CII] luminosity- FWHM relations, and discuss its redshift evolution and a possible cosmological application.


Keywords: High-z galaxy, CII observation, CO observation, Cosmological constraints