Original title: Multi-tracer exploration of molecular gas in main sequence galaxies at z~4.5
M. Dessauges-Zavadsky, M. Béthermin, M. Ginolfi, L. Vallini +14 · September 2026
Astronomers want to measure molecular gas, the fuel that forms stars, in early galaxies. Because this gas is hard to see directly, scientists use indirect signposts called tracers, such as bright light from carbon ions known as [CII]. But they need to know if [CII] gives reliable measurements. Researchers looked for carbon monoxide, or CO, and neutral carbon in three galaxies at redshift z~4.5. Different tracers emit specific light signals that reveal how much gas is present. In one galaxy with near-solar metallicityThe abundance of elements heavier than hydrogen and helium in a galaxy, affecting how tracers behave., gas masses from six different methods matched well. This shows standard tools used for later cosmic eras still work there. However, in a galaxy with half-solar metallicity, they detected no CO gas. In a merging galaxy pair, [CII] light was unusually high, likely boosted by shocks or diffuse ionized gas rather than regular cold molecular gas.
You're estimating how much flour is in a bag by weighing it, measuring its height, or tapping it to hear the sound. If the bag is lumpy or has air pockets, the sound method might give a wrong estimate. In this paper, astronomers use different signals like [CII] and CO to measure gas in galaxies. In merging galaxies, the [CII] signal is affected by shocks and extra gas, making it unreliable compared to other methods.
Astronomers rely on [CII] light to estimate gas in distant galaxies. If this method fails in mergers, our understanding of early galaxy growth could be based on incorrect data.
The study only examined three galaxies, so the results may not apply to all high-redshift galaxies. The undetected [CI] lines provide no comparison for that tracer. The findings are specific to near-solar metallicity and merging conditions, and broader validation is needed.
Ask anything about this paper. Answers come from its abstract, and say so when the abstract doesn't cover your question.
Multi-tracer exploration of molecular gas in main sequence galaxies at z~4.5 — M. Dessauges-Zavadsky, M. Béthermin, M. Ginolfi et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.