ColdSIM predictions of [C II] emission in primordial galaxies

TL;DR

This paper uses advanced hydrodynamic simulations to study the [C II] 158 μm emission line in primordial galaxies, predicting its evolution, environmental dependencies, and correlations with galaxy properties at high redshift.

Contribution

It introduces the ColdSIM simulation framework with non-equilibrium chemistry to accurately predict [C II] emission and its relation to galaxy properties in the early universe.

Findings

Predicted cosmic [C II] mass density evolution aligns with observations at z=6.

Established a correlation between [C II] luminosity and stellar mass.

Provided a new fit for [C II] luminosity and SFR relation.

Abstract

A powerful tool to probe the gas content at high redshift is the [C II] 158 $\mu$m sub-millimeter emission line, which, due to its low excitation potential and luminous emission, is considered a possible direct tracer of star forming gas. In this work we investigate the origin, evolution and environmental dependencies of [C II] 158 $\mu$m emission line, as well as its expected correlation with stellar mass and star formation activity of the high-redshift galaxies observed by JWST. We use a set of state-of-the-art cold-gas hydrodynamic simulations (ColdSIM) with fully coupled time-dependent atomic and molecular non-equilibrium chemistry and self-consistent [C II] emission from metal enriched gas. We accurately track the evolution of H I, H II and $H_2$ in a cosmological context and predict both global and galaxy-based [C II] properties. For the first time, we predict the cosmic mass density evolution of [C II] and find that it is in good agreement with new measurements at redshift z = 6 from high-resolution optical quasar spectroscopy. We find a correlation between [C II] luminosity, $L_{[C II]}$, and stellar mass, consistent with results from ALMA high-redshift large programs. We predict a redshift evolution in the relation between $L_{[C II]}$ and the star formation rate, SFR, and provide a fit to relate $L_{[C II]}$ to SFR which can be adopted as a more accurate alternative to the currently used linear relation. Our findings provide physical grounds to interpret high-redshift detections in contemporary and future observations, such as the ones performed by ALMA and JWST, and to advance our knowledge on structure formation at early times.