2025/08/13 by Topkaras, Theodoros, Bisbas, Thomas G., Zhang, Zhi-Yu +1
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2508.09951
Context. Cold molecular gas tracers, such as CI and CO lines, have been widely used to infer specific characteristics of the ISM and to derive star-formation relations among galaxies. Aims. However, there is still a lack of systematic studies of the star-formation scaling relation of CO and [CI] lines across cosmic time on multiple physical scales. Methods. We used observations of the ground state transitions of [CI], CO, and [CII], for 885 sources collected from the literature, to infer possible correlations between line luminosities of \rm L'[CI](1-0), \rm L'CO(1-0), and \rm L'[CII] with star formation rates (SFR). With linear regression, we fit the relations between SFR and molecular mass derived from CO, CI, and CII lines. Results. The relation between [CI] and CO-based total molecular masses is weakly superlinear. Nevertheless, they can be calibrated against each other. For \rm αCO = 0.8 and 4.0 \rm M\odot (K km s-1 pc2)-1 we derive α\rm [CI] = 3.9 and ∼17 \rm M\odot (K km s-1 pc2)-1 , respectively. Using the lmfit package, we derived relation slopes of SFR--\rm L'[CI](1-0), SFR--\rm L'CO(1-0), and SFR--\rm L'[CII](1-0) to be \rm β = 1.06 ± 0.02, 1.24 ± 0.02, and 0.74 ± 0.02, respectively. With a Bayesian-inference linmix method, we find consistent results. Conclusions. Our relations for [CI](1-0) and CO(1-0) indicate that they trace similar molecular gas contents, across different redshifts and different types of galaxies. This suggests that these correlations do not have strong evolution with cosmic time.