Abstract

Contributed Talk - Splinter GalaxyEvol

Friday, 13 September 2024, 15:24   (S21)

Tight correlation of star formation with [CI] and CO lines across cosmic time

Theodoros Topkaras, Thomas Bisbas , Zhi-Yu Zhang, V. Ossenkopf-Okada
PH1, Zhejiang Lab, Nanjing, PH1

The interstellar medium (ISM) consists of the matter and radiation within a galaxy. One of its key components, cold molecular gas, is the one that plays a significant role in star formation and evolution of galaxies. Studying the process by which cold molecular gas forms stars is essential to understanding the evolution of a galaxy. Cold molecular gas tracers, such as [CI] and CO, are extensively used to infer specific characteristics of the ISM. These molecules are also instrumental in exploring potential relationships between the star formation rate (SFR) and the corresponding computed luminosities of each species, based on the total fluxes, across different galaxy types and redshifts. Relations between SFR and the ground state of CO, namely the CO(1-0) transition, have previously been made across the literature. As the ground state transition of [CI](1-0) becomes more and more trustworthy as a cold molecular gas tracer, it is important to investigate how/if SFR correlates with it. In the present study, we investigate the SFR versus the corresponding species prime luminosity (line luminosity that is proportional to the brightness temperature) scaling relation of CO, [CI] and [CII] across different cosmic epochs, shedding light on the processes governing the molecular gas and star formation on various scales. We have used the largest sample of sources, to this date, that have both CO(1-0) and [CI](1-0) observations, comprising 381 sources. By utilizing the aforementioned gas tracers we probe the sources’ luminosities, total molecular hydrogen masses, and SFRs. We identify a discrepancy in the total molecular masses computed using [CI] compared to CO when maintaining a fixed ’conversion factor’ of αCO = 0.8 M⊙ (K km s−1 pc2)−1. We deduce that a C/H2 abundance ratio of 2.3 times higher than the ’standard’ adopted value (χC = 3 × 10−5), is needed to bring the two masses in agreement. Finally, we perform two regression model fits, correlating the SFR with L′[CI(1−0), L′CO(1−0) and L′[CII]. The result of these fits provides tight correlations of SFR with the utilized gas tracers that do not have a strong evolution with cosmic time.