Molecular Gas Detections in Eight Faint DSFGs with Red NIR Colors at z = 1.2-2.5
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2026
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| author | Rosenthal, Michael J. Nicandro McKay, Stephen J. Barger, Amy J. Cowie, Lennox L. |
| author_facet | Rosenthal, Michael J. Nicandro McKay, Stephen J. Barger, Amy J. Cowie, Lennox L. |
| contents | We present a NOEMA survey of CO(3-2), CO(4-3), and [C I]($^3$P$_1$-$^3$P$_0$) in eight faint (average $S_{\rm 850 μm} = 2.3$ mJy) dusty star-forming galaxies (DSFGs) at $z = 1.2-2.5$. We used a NIR flux-color cut to match faint SCUBA-2 sources to red stellar counterparts with existing spectroscopic redshifts, allowing us to target CO lines at known frequencies. We obtained seven new CO detections and a serendipitous [C I] detection in an off-axis source, and measured molecular gas masses of $M_{\rm mol} = (6-22)\times10^{10}~(α_{\rm CO}/3.6)~{\rm M}_\odot$ from these lines. We performed UV-to-mm SED fits to measure the SFRs and stellar masses of our sample, and compared these with two other $z = 1-3$ CO samples from the literature. The CO detections have constant depletion times of $t_{\rm dep} \sim 500$ Myr, with no evidence for correlation between $t_{\rm dep}$ and redshift or main-sequence offset. We find that low-mass ($M_\star \lesssim 10^{11}~{\rm M}_\odot$), starbursting galaxies have gas fractions and depletion times twice as high as predicted by molecular gas scaling relations, which may indicate that $M_{\rm mol}$ is systematically over-estimated in this population, possibly due to decreased $α_{\rm CO}$ or increased CO excitation compared to the well-studied massive and/or main-sequence DSFG population. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_20862 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Molecular Gas Detections in Eight Faint DSFGs with Red NIR Colors at z = 1.2-2.5 Rosenthal, Michael J. Nicandro McKay, Stephen J. Barger, Amy J. Cowie, Lennox L. Astrophysics of Galaxies We present a NOEMA survey of CO(3-2), CO(4-3), and [C I]($^3$P$_1$-$^3$P$_0$) in eight faint (average $S_{\rm 850 μm} = 2.3$ mJy) dusty star-forming galaxies (DSFGs) at $z = 1.2-2.5$. We used a NIR flux-color cut to match faint SCUBA-2 sources to red stellar counterparts with existing spectroscopic redshifts, allowing us to target CO lines at known frequencies. We obtained seven new CO detections and a serendipitous [C I] detection in an off-axis source, and measured molecular gas masses of $M_{\rm mol} = (6-22)\times10^{10}~(α_{\rm CO}/3.6)~{\rm M}_\odot$ from these lines. We performed UV-to-mm SED fits to measure the SFRs and stellar masses of our sample, and compared these with two other $z = 1-3$ CO samples from the literature. The CO detections have constant depletion times of $t_{\rm dep} \sim 500$ Myr, with no evidence for correlation between $t_{\rm dep}$ and redshift or main-sequence offset. We find that low-mass ($M_\star \lesssim 10^{11}~{\rm M}_\odot$), starbursting galaxies have gas fractions and depletion times twice as high as predicted by molecular gas scaling relations, which may indicate that $M_{\rm mol}$ is systematically over-estimated in this population, possibly due to decreased $α_{\rm CO}$ or increased CO excitation compared to the well-studied massive and/or main-sequence DSFG population. |
| title | Molecular Gas Detections in Eight Faint DSFGs with Red NIR Colors at z = 1.2-2.5 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2601.20862 |