COMAP Pathfinder – Season 2 results

We present a stack of data from the second season of the CO Mapping Array Project (COMAP) on the positions of quasars from eBOSS and DESI. COMAP is a line intensity mapping (LIM) experiment targeting dense molecular gas via CO(1–0) emission at z ∼ 3. Season 2 of COMAP represents a factor of three increase in map-level sensitivity over the previous early science data release. We do not detect any CO emission in the stack; instead, we find an upper limit of 10.0 × 10 10 K km s −1 pc 2 at 95% confidence within an ∼18 cMpc box. We compare this upper limit to models of the CO emission stacked on quasars and find a tentative (∼3 σ ) tension between the limit and the brightest stack models after accounting for a suite of additional sources of experimental attenuation and uncertainty, including quasar velocity uncertainty, pipeline signal loss, cosmic variance, and interloper emission in the LIM data. The COMAP-eBOSS/DESI stack is primarily a measurement of the CO luminosity in the quasars’ wider environment, and is therefore potentially subject to environmental effects such as feedback. With our current simple models of the galaxy-halo connection, we are thus unable to confidently rule out any models of cosmic CO with the stack alone. Conversely, the stack’s sensitivity to these large-scale environmental effects has the potential to make it a powerful tool for galaxy formation science, once we are able to constrain the average CO luminosity via the auto-power spectrum (a key goal of COMAP).

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Journal
Astronomy and Astrophysics
Published
2026-02-12
DOI
https://doi.org/10.1051/0004-6361/202557864
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
0.00

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article

COMAP Pathfinder – Season 2 results

N. Stutzer, K. A. Cleary, P. C. Breysse, D. T. Chung et al.
Astronomy and Astrophysics
Galaxies: Formation, Evolution, Phenomena
article

COMAP Pathfinder – Season 2 results

N. Stutzer, K. A. Cleary, P. C. Breysse, D. T. Chung, J. Y. Kim, S. R. Mason, I. K. Wehus, H. K. Eriksen, D. A. Dunne, J. G. S. Lunde, S. Valentine, J. R. Bond, N. Murray, E. M. Mansfield, J. O. Gundersen, G. A. Hoerning, D. Tolgay
article en

Abstract

We present a stack of data from the second season of the CO Mapping Array Project (COMAP) on the positions of quasars from eBOSS and DESI. COMAP is a line intensity mapping (LIM) experiment targeting dense molecular gas via CO(1–0) emission at z ∼ 3. Season 2 of COMAP represents a factor of three increase in map-level sensitivity over the previous early science data release. We do not detect any CO emission in the stack; instead, we find an upper limit of 10.0 × 10 10 K km s −1 pc 2 at 95% confidence within an ∼18 cMpc box. We compare this upper limit to models of the CO emission stacked on quasars and find a tentative (∼3 σ ) tension between the limit and the brightest stack models after accounting for a suite of additional sources of experimental attenuation and uncertainty, including quasar velocity uncertainty, pipeline signal loss, cosmic variance, and interloper emission in the LIM data. The COMAP-eBOSS/DESI stack is primarily a measurement of the CO luminosity in the quasars’ wider environment, and is therefore potentially subject to environmental effects such as feedback. With our current simple models of the galaxy-halo connection, we are thus unable to confidently rule out any models of cosmic CO with the stack alone. Conversely, the stack’s sensitivity to these large-scale environmental effects has the potential to make it a powerful tool for galaxy formation science, once we are able to constrain the average CO luminosity via the auto-power spectrum (a key goal of COMAP).

Astronomy and AstrophysicsVol. 707
California Institute of Technology (US), University of British Columbia (CA), University of Miami (US), Korea Advanced Institute of Science and Technology (KR), Southern Methodist University (US), University of Oslo (NO), University of Toronto (CA), Cornell University (US), SKA Observatory (GB), Canadian Institute for Theoretical Astrophysics (CA), Institute of Theoretical Physics (CN), Astronomy and Space (AU)
National Science Foundation, U.S. Department of Defense, Smithsonian Institution, U.S. Department of Energy, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, Vanderbilt University, University of Miami, Ohio State University, Keck Institute for Space Studies, University of Utah, University of Washington, Johns Hopkins University, Carnegie Mellon University, University of Notre Dame, University of Portsmouth, New Mexico State University, York University, University of Oxford, Ministério da Ciência, Tecnologia e Inovação, Universidad Nacional Autónoma de México, Max-Planck-Institut für Astrophysik, Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Canarias, Office of Science, University of Colorado Boulder, Leibniz-Gemeinschaft, Division of Astronomical Sciences, Lawrence Berkeley National Laboratory
Life in Land
Openalex Percentile: Top 56%
Galaxies: Formation, Evolution, Phenomena
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