The Extended Mapping Obscuration to Reionization with ALMA (Ex-MORA) Survey: A Molecular Gas Line Search
Abstract
Current investigations of cold gas in the interstellar medium face selection biases, as optical/near-infrared surveys favor massive, low-obscuration galaxies and miss gas-rich passive or inefficient star-forming systems. Overcoming this requires large-volume line surveys selected by molecular gas rather than stellar luminosity. We present a molecular gas census across 0.5 < z < 5 using ALMA Band 4 observations from the Extended Mapping of Obscuration to Reionization Survey (Ex-MORA), covering 577 arcmin2. Combining an unbiased search for bright emitters with a targeted search using spectroscopic redshift priors, we detect 52 galaxies in CO or \ci transitions (two showing two lines). Physical properties were derived via \texttt{CIGALE} with non-parametric star-formation histories, and gas masses were estimated using metallicity-dependent conversion factors. The sample is dominated by main-sequence (MS) galaxies with high stellar masses (median log M*/M⊙ = 10.83) and large gas reservoirs (>1010 M⊙). Gas fraction (μgas) increases with redshift for active populations, though high-redshift trends are influenced by a gas-rich protocluster at z ≈ 2.4. Conversely, an overdensity at z ≈ 0.73 mirrors the field population. Five Green Valley (GV) galaxies exhibit a μgas peak at cosmic noon, suggesting stellar feedback may suppress star formation by heating gas rather than rapidly depleting it in at least some transitional systems. Resolved kinematics show a prevalence of rotating disks. These results demonstrate that wide-area line searches effectively recover massive gas reservoirs across diverse evolutionary stages
Related
- IRAC-Excess Galaxies in the NIRSpec Wide Survey: physical properties of bright EELGs at z∼7 and implications for Reionization
- The JWST Emission Line Survey (JELS): A narrow-band determination of the Hα Luminosity Function and Cosmic Star Formation into the Epoch of Reionization
- JWST lensed quasar dark matter survey. IV. Stringent warm dark matter constraints from the joint reconstruction of extended lensed arcs and quasar flux ratios
- GATOS XV: A JWST/MIRI survey of extended circumnuclear dust emission in nearby Seyfert galaxies
- The rise and decline of a transient obscuration event in a moderately distant type-I quasar
BibTeX
@misc{catan2026extended,
title = {{The Extended Mapping Obscuration to Reionization with ALMA (Ex-MORA) Survey: A Molecular Gas Line Search}},
author = {V. Catán and J. González-López and M. Aravena and A. S. Long and C. M. Casey and D. L. Clements and E. da Cunha and M. Franco and A. M. Koekemoer and A. Man and J. Spilker and E. Treister},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.10165},
eprint = {2608.10165},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.10165},
}
RIS
TY - UNPB
TI - The Extended Mapping Obscuration to Reionization with ALMA (Ex-MORA) Survey: A Molecular Gas Line Search
AU - V. Catán
AU - J. González-López
AU - M. Aravena
AU - A. S. Long
AU - C. M. Casey
AU - D. L. Clements
AU - E. da Cunha
AU - M. Franco
AU - A. M. Koekemoer
AU - A. Man
AU - J. Spilker
AU - E. Treister
PY - 2026
DA - 2026/08/31
PB - arXiv
DO - 10.48550/arxiv.2608.10165
UR - https://arxiv.org/abs/2608.10165
AB - Current investigations of cold gas in the interstellar medium face selection biases, as optical/near-infrared surveys favor massive, low-obscuration galaxies and miss gas-rich passive or inefficient star-forming systems. Overcoming this requires large-volume line surveys selected by molecular gas rather than stellar luminosity. We present a molecular gas census across 0.5 < z < 5 using ALMA Band 4 observations from the Extended Mapping of Obscuration to Reionization Survey (Ex-MORA), covering 577 arcmin^2. Combining an unbiased search for bright emitters with a targeted search using spectroscopic redshift priors, we detect 52 galaxies in CO or \ci transitions (two showing two lines). Physical properties were derived via \texttt{CIGALE} with non-parametric star-formation histories, and gas masses were estimated using metallicity-dependent conversion factors. The sample is dominated by main-sequence (MS) galaxies with high stellar masses (median log M_*/M_⊙ = 10.83) and large gas reservoirs (>10^10 M_⊙). Gas fraction (μ_gas) increases with redshift for active populations, though high-redshift trends are influenced by a gas-rich protocluster at z ≈ 2.4. Conversely, an overdensity at z ≈ 0.73 mirrors the field population. Five Green Valley (GV) galaxies exhibit a μ_gas peak at cosmic noon, suggesting stellar feedback may suppress star formation by heating gas rather than rapidly depleting it in at least some transitional systems. Resolved kinematics show a prevalence of rotating disks. These results demonstrate that wide-area line searches effectively recover massive gas reservoirs across diverse evolutionary stages
ER -