COMAP Pathfinder – Season 2 results

II. Updated constraints on the CO(1–0) power spectrum

¹ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
² California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
³ Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8, Canada
⁴ Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
⁵ Department of Astronomy, Cornell University, Ithaca, NY 14853, USA
⁶ Center for Cosmology and Particle Physics, Department of Physics, New York University, 726 Broadway, New York, NY 10003, USA
⁷ Department of Physics, Southern Methodist University, Dallas, TX 75275, USA
⁸ Departement de Physique Théorique, Universite de Genève, 24 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland
⁹ Owens Valley Radio Observatory, California Institute of Technology, Big Pine, CA 93513, USA
¹⁰ Jodrell Bank Centre for Astrophysics, Alan Turing Building, Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
¹¹ Department of Physics and Astronomy, University of British Columbia, Vancouver, BC Canada V6T 1Z1, Canada
¹² Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
¹³ Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
¹⁴ Department of Physics, University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7, Canada
¹⁵ David A. Dunlap Department of Astronomy, University of Toronto, 50 St. George Street, Toronto, ON, M5S 3H4, Canada
¹⁶ Brookhaven National Laboratory, Upton, NY 11973-5000, USA
¹⁷ Kavli Institute for Particle Astrophysics and Cosmology and Physics Department, Stanford University, Stanford, CA 94305, USA
¹⁸ Department of Physics, University of Miami, 1320 Campo Sano Avenue, Coral Gables, FL 33146, USA
¹⁹ Department of Astronomy, University of Maryland, College Park, MD 20742, USA

^★ Corresponding author; n.o.stutzer@astro.uio.no

Received: 14 June 2024
Accepted: 30 August 2024

Abstract

We present updated constraints on the cosmological 3D power spectrum of carbon monoxide CO(1–0) emission in the redshift range 2.4–3.4. The constraints are derived from the two first seasons of Carbon monOxide Mapping Array Project (COMAP) Pathfinder line intensity mapping observations aiming to trace star formation during the epoch of galaxy assembly. These results improve on the previous Early Science results through both increased data volume and an improved data processing methodology. On the methodological side, we now perform cross-correlations between groups of detectors (“feed groups”), as opposed to cross-correlations between single feeds, and this new feed group pseudo power spectrum (FGPXS) is constructed to be more robust against systematic effects. In terms of data volume, the effective mapping speed is significantly increased due to an improved observational strategy as well as a better data selection methodology. The updated spherically and field-averaged FGPXS, C^~(k), is consistent with zero, at a probability-to-exceed of around 34%, with an excess of 2.7 σ in the most sensitive bin. Our power spectrum estimate is about an order of magnitude more sensitive in our six deepest bins across 0.09 Mpc⁻¹ < k < 0.73 Mpc⁻¹, compared to the feed-feed pseudo power spectrum (FPXS) of COMAP ES. Each of these bins individually constrains the CO power spectrum to k P_CO(k) < 2400–4900 μK²Mpc² at 95% confidence. To monitor potential contamination from residual systematic effects, we analyzed a set of 312 difference-map null tests and found that these are consistent with the instrumental noise prediction. In sum, these results provide the strongest direct constraints on the cosmological 3D CO(1–0) power spectrum published to date.