The interstellar medium of high-redshift galaxies: Gathering clues from C III] and [C II] lines

• Published in: arXiv.org 2022-06
• Main Authors: Markov, Vladan, Carniani, Stefano, Vallini, Livia, Ferrara, Andrea, Pallottini, Andrea, Maiolino, Roberto, Gallerani, Simona, Pentericci, Laura
• Format: Article
• Language: English
• Subjects: Algorithms; Deviation; Emission; Galaxies; Gas density; Interstellar matter; Luminosity; Metallicity; Red shift; Star & galaxy formation; Star formation rate
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2206.03503

A tight relation between [C II] line luminosity and the star formation rate (SFR) has been observed for local galaxies. At high redshift (z > 5), galaxies instead deviate downwards from the local \(\Sigma\)_[C II] - \(\Sigma\)_SFR relation. This deviation might be caused by different interstellar medium (ISM) properties in galaxies at early epochs. To test this hypothesis, we combined the [C II] and SFR data with C III] line observations and our physical models. We additionally investigated how ISM properties, such as burstiness, \(\kappa_s\), total gas density, \(n\), and metallicity, \(Z\), affect the deviation from the \(\Sigma\)_[C II] - \(\Sigma\)_SFR relation in these sources. We present the VLT/X-SHOOTER observations targeting the C III] \({\lambda}1909\) line emission in three galaxies at 5.5 < z < 7. We include X-SHOOTER and VLT/MUSE archival data of eight galaxies at 2 < z < 7, and eleven star-forming systems at 6 < z < 7.5, with either C III] or [C II] detection reported in the literature. We detected C III] \({\lambda}{\lambda}1907, 1909\) line emission in HZ10 and we derived the intrinsic, integrated flux of the C III] \({\lambda}1909\) line. We constrained the ISM properties for our sample of galaxies, \(\kappa_s\) , \(n\), and \(Z\), by applying our physically motivated model based on the MCMC algorithm. For the most part, high-z star-forming galaxies show subsolar metallicities. The majority of the sources have \(log(\kappa_s) > 1\), that is, they overshoot the Kennicutt-Schmidt (KS) relation by about one order of magnitude, implying that the whole KS relation might be shifted upwards at early times. Furthermore, all the high-z galaxies of our sample lie below the \(\Sigma\)_[C II] - \(\Sigma\)_SFR local relation. The total gas density, \(n\), shows the strongest correlation with the deviation from the local \(\Sigma\)_[C II] - \(\Sigma\)_SFR relation.