Modeling CO Line Luminosity with FIRE simulations: II. Comparison With Observations, CO Luminosity Functions and Redshift Evolution
Abstract
We present predictions for the CO(1-0) and CO(2-1) luminosities of 765, 850, 887 and 915 galaxies at z=0, 1, 2 and 3, respectively, drawn from the Feedback in Realistic Environments (FIRE-2) simulations and post-processed with SKIRT radiative transfer and CLOUDY line emission calculations. We compare our CO line luminosity predictions with existing observations. At z=0, our predictions reproduce the observed scatter and mean relation between star formation rate (SFR) and CO(1-0) luminosity for both massive star-forming galaxies and low-metallicity dwarf galaxies. We also reproduce the observed superlinear power-law slope between CO(1-0) luminosity and metallicity. At z=1, our CO(2-1) predictions scatter to much lower luminosities than observed, which likely reflects the limited sensitivity of current surveys. At fixed SFR, our CO(1-0) luminosities decrease by roughly an order of magnitude per unit increase in redshift. This decline is likely driven by the decrease in metallicity with increasing redshift, since FIRE-2 galaxies with comparable SFR and metallicity produce similar CO(1-0) luminosities regardless of redshift. At fixed stellar mass, the predicted luminosities show no redshift dependence. These results show that our FIRE-2 predictions reproduce the observed scaling relations between CO(1-0) luminosity and galaxy properties wherever the observed galaxies are robustly detected. This gives us confidence in our predictions for the regime where no observational data exist, and suggests that our luminosity predictions can be used to build predictive models for CO line intensity mapping experiments.
Related
- Galaxy luminosity functions from far-UV to submillimetre at z=0 in the COLIBRE simulations
- Galaxy Luminosity Functions at z~7-10 from Four Years of JWST Observations
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- The Galaxy Luminosity Functions in ASTRID: Predictions for LSST
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BibTeX
@misc{tolgay2026modeling,
title = {{Modeling CO Line Luminosity with FIRE simulations: II. Comparison With Observations, CO Luminosity Functions and Redshift Evolution}},
author = {Doğa Tolgay and J. Richard Bond and Norman W. Murray and Dongwoo Chung and Robert Feldmann and Andrew Wetzel},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.00368},
eprint = {2611.00368},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.00368},
}
RIS
TY - UNPB
TI - Modeling CO Line Luminosity with FIRE simulations: II. Comparison With Observations, CO Luminosity Functions and Redshift Evolution
AU - Doğa Tolgay
AU - J. Richard Bond
AU - Norman W. Murray
AU - Dongwoo Chung
AU - Robert Feldmann
AU - Andrew Wetzel
PY - 2026
DA - 2026/11/01
PB - arXiv
DO - 10.48550/arxiv.2611.00368
UR - https://arxiv.org/abs/2611.00368
AB - We present predictions for the CO(1-0) and CO(2-1) luminosities of 765, 850, 887 and 915 galaxies at z=0, 1, 2 and 3, respectively, drawn from the Feedback in Realistic Environments (FIRE-2) simulations and post-processed with SKIRT radiative transfer and CLOUDY line emission calculations. We compare our CO line luminosity predictions with existing observations. At z=0, our predictions reproduce the observed scatter and mean relation between star formation rate (SFR) and CO(1-0) luminosity for both massive star-forming galaxies and low-metallicity dwarf galaxies. We also reproduce the observed superlinear power-law slope between CO(1-0) luminosity and metallicity. At z=1, our CO(2-1) predictions scatter to much lower luminosities than observed, which likely reflects the limited sensitivity of current surveys. At fixed SFR, our CO(1-0) luminosities decrease by roughly an order of magnitude per unit increase in redshift. This decline is likely driven by the decrease in metallicity with increasing redshift, since FIRE-2 galaxies with comparable SFR and metallicity produce similar CO(1-0) luminosities regardless of redshift. At fixed stellar mass, the predicted luminosities show no redshift dependence. These results show that our FIRE-2 predictions reproduce the observed scaling relations between CO(1-0) luminosity and galaxy properties wherever the observed galaxies are robustly detected. This gives us confidence in our predictions for the regime where no observational data exist, and suggests that our luminosity predictions can be used to build predictive models for CO line intensity mapping experiments.
ER -