[CII] as a global cold gas tracer in novel hydrodynamical simulations
Abstract
[CII] emission is a powerful tool for studying the gas content in galaxies, especially at early stages of evolution. Given its low excitation potential, the [CII] 158 μm line is the main coolant of neutral gas in photodissociation regions and giant molecular clouds, hence a tracer of all phases of the interstellar medium. However, there is no consensus on what is the nature of the gas traced by this emission. We aim to provide insights into the physics of the [CII] emission and predictions for future observations. We used four pre-prepared simulations performed with a version of p-gadget-3, which includes the krome chemistry package. We implemented a postprocessing semi-analytical model to simulate the [CII] emission. We analysed an isolated Milky Way-mass-size galaxy, and three merger configurations: a co-rotating, counter-rotating, and perpendicular major mergers of two Milky Way-mass-size galaxies. We reproduce fundamental relations such as the [CII] luminosity and the star formation rate, L[CII]-SFR relation, in which mergers show an extra component for the [CII] emission not traced by the star formation alone. During quiescent or starburst stages, galaxies deviate from the L[CII]-SFR relation. We find that [CII] is a robust tracer of molecular gas, as well as atomic gas in both cold and warm phases on a global scale. Our results indicate that around 50 per cent of the total [CII] emission is traced by molecular gas, while 30 to 40 per cent is traced by atomic and ionised hydrogen regardless of the configuration. Our findings suggest that the nature of the [CII] emission depends strongly on the evolutionary history of galaxies, in which mergers and starbursts act as more efficient drivers of [CII] emission through collision with molecular hydrogen.
Versions
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BibTeX
@misc{miranda2026global,
title = {{[CII] as a global cold gas tracer in novel hydrodynamical simulations}},
author = {Valentina P. Miranda and Patricia B. Tissera and Jorge González-López and Emanuel Sillero},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2608.22080},
eprint = {2608.22080},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.22080},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - [CII] as a global cold gas tracer in novel hydrodynamical simulations
AU - Valentina P. Miranda
AU - Patricia B. Tissera
AU - Jorge González-López
AU - Emanuel Sillero
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2608.22080
UR - https://arxiv.org/abs/2608.22080
AB - [CII] emission is a powerful tool for studying the gas content in galaxies, especially at early stages of evolution. Given its low excitation potential, the [CII] 158 μm line is the main coolant of neutral gas in photodissociation regions and giant molecular clouds, hence a tracer of all phases of the interstellar medium. However, there is no consensus on what is the nature of the gas traced by this emission. We aim to provide insights into the physics of the [CII] emission and predictions for future observations. We used four pre-prepared simulations performed with a version of p-gadget-3, which includes the krome chemistry package. We implemented a postprocessing semi-analytical model to simulate the [CII] emission. We analysed an isolated Milky Way-mass-size galaxy, and three merger configurations: a co-rotating, counter-rotating, and perpendicular major mergers of two Milky Way-mass-size galaxies. We reproduce fundamental relations such as the [CII] luminosity and the star formation rate, L[CII]-SFR relation, in which mergers show an extra component for the [CII] emission not traced by the star formation alone. During quiescent or starburst stages, galaxies deviate from the L[CII]-SFR relation. We find that [CII] is a robust tracer of molecular gas, as well as atomic gas in both cold and warm phases on a global scale. Our results indicate that around 50 per cent of the total [CII] emission is traced by molecular gas, while 30 to 40 per cent is traced by atomic and ionised hydrogen regardless of the configuration. Our findings suggest that the nature of the [CII] emission depends strongly on the evolutionary history of galaxies, in which mergers and starbursts act as more efficient drivers of [CII] emission through collision with molecular hydrogen.
ER -