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COMAP Early Science. III. CO Data Processing

Foss, Marie K. and Ihle, Håvard T. and Borowska, Jowita and Cleary, Kieran A. and Eriksen, Hans Kristian and Harper, Stuart E. and Kim, Junhan and Lamb, James W. and Lunde, Jonas G. S. and Philip, Liju and Rasmussen, Maren and Stutzer, Nils-Ole and Uzgil, Bade D. and Watts, Duncan J. and Wehus, Ingunn K. and Woody, David P. and Bond, J. Richard and Breysse, Patrick C. and Catha, Morgan and Church, Sarah E. and Chung, Dongwoo T. and Dickinson, Clive and Dunne, Delaney A. and Gaier, Todd and Gundersen, Joshua Ott and Harris, Andrew I. and Hobbs, Richard and Lawrence, Charles R. and Murray, Norman and Readhead, Anthony C. S. and Padmanabhan, Hamsa and Pearson, Timothy J. and Rennie, Thomas J. (2022) COMAP Early Science. III. CO Data Processing. Astrophysical Journal, 933 (2). Art. No. 184. ISSN 0004-637X. doi:10.3847/1538-4357/ac63ca.

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We describe the first-season CO Mapping Array Project (COMAP) analysis pipeline that converts raw detector readouts to calibrated sky maps. This pipeline implements four main steps: gain calibration, filtering, data selection, and mapmaking. Absolute gain calibration relies on a combination of instrumental and astrophysical sources, while relative gain calibration exploits real-time total-power variations. High-efficiency filtering is achieved through spectroscopic common-mode rejection within and across receivers, resulting in nearly uncorrelated white noise within single-frequency channels. Consequently, near-optimal but biased maps are produced by binning the filtered time stream into pixelized maps; the corresponding signal bias transfer function is estimated through simulations. Data selection is performed automatically through a series of goodness-of-fit statistics, including χ² and multiscale correlation tests. Applying this pipeline to the first-season COMAP data, we produce a data set with very low levels of correlated noise. We find that one of our two scanning strategies (the Lissajous type) is sensitive to residual instrumental systematics. As a result, we no longer use this type of scan and exclude data taken this way from our Season 1 power spectrum estimates. We perform a careful analysis of our data processing and observing efficiencies and take account of planned improvements to estimate our future performance. Power spectrum results derived from the first-season COMAP maps are presented and discussed in companion papers.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Foss, Marie K.0000-0001-8896-3159
Ihle, Håvard T.0000-0003-3420-7766
Cleary, Kieran A.0000-0002-8214-8265
Eriksen, Hans Kristian0000-0003-2332-5281
Harper, Stuart E.0000-0001-7911-5553
Kim, Junhan0000-0002-4274-9373
Lamb, James W.0000-0002-5959-1285
Philip, Liju0000-0001-7612-2379
Stutzer, Nils-Ole0000-0001-5301-1377
Uzgil, Bade D.0000-0001-8526-3464
Watts, Duncan J.0000-0002-5437-6121
Wehus, Ingunn K.0000-0003-3821-7275
Bond, J. Richard0000-0003-2358-9949
Breysse, Patrick C.0000-0001-8382-5275
Chung, Dongwoo T.0000-0003-2618-6504
Dickinson, Clive0000-0002-0045-442X
Dunne, Delaney A.0000-0002-5223-8315
Harris, Andrew I.0000-0001-6159-9174
Readhead, Anthony C. S.0000-0001-9152-961X
Padmanabhan, Hamsa0000-0002-8800-5740
Pearson, Timothy J.0000-0001-5213-6231
Rennie, Thomas J.0000-0002-1667-3897
Alternate Title:COMAP Early Science: III. CO Data Processing
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 November 19; revised 2022 February 25; accepted 2022 March 15; published 2022 July 13. Focus on Early Science Results from the CO Mapping Array Project (COMAP) We thank graduated master student Erik Levén for his contribution to this work. This material is based on work supported by the National Science Foundation under grant Nos. 1517108, 1517288, 1517598, 1518282, and 1910999 and by the Keck Institute for Space Studies under "The First Billion Years: A Technical Development Program for Spectral Line Observations." Parts of the work were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration, and funded through the internal Research and Technology Development program. D.T.C. is supported by a CITA/Dunlap Institute postdoctoral fellowship. The Dunlap Institute is funded through an endowment established by the David Dunlap family and the University of Toronto. C.D. acknowledges support from an STFC Consolidated Grant (ST/P000649/1). J.B., H.K.E., M.K.F., H.T.I., J.G.S.L., M.R., N.-O.S., D.W., and I.K.W. acknowledge support from the Research Council of Norway through grants 251328 and 274990 and from the European Research Council (ERC) under the Horizon 2020 Research and Innovation Program (grant agreement No. 819478, Cosmoglobe). J.G. acknowledges support from the University of Miami and is grateful to Hugh Medrano for assistance with cryostat design. S.H. acknowledges support from an STFC Consolidated Grant (ST/P000649/1). J. Kim is supported by a Robert A. Millikan Fellowship from Caltech. At JPL, we are grateful to Mary Soria for assembly work on the amplifier modules and to Jose Velasco, Ezra Long, and Jim Bowen for the use of their amplifier test facilities. H.P. acknowledges support from the Swiss National Science Foundation through Ambizione grant PZ00P2_179934. P.C.B. is supported by the James Arthur Postdoctoral Fellowship. We thank Isu Ravi for her contributions to the warm electronics and antenna drive characterization. The Scientific color maps roma and tokyo (Crameri 2021) are used in this study to prevent visual distortion of the data and exclusion of readers with color-vision deficiencies (Crameri et al. 2020). We also want to thank the anonymous referee, whose comments and suggestions have helped to significantly improve and clarify this manuscript. Software: Matplotlib (Hunter 2007); Astropy, a community-developed core Python package for astronomy (Astropy Collaboration et al. 2013).
Group:Astronomy Department, Owens Valley Radio Observatory (OVRO), Keck Institute for Space Studies
Funding AgencyGrant Number
Keck Institute for Space Studies (KISS)UNSPECIFIED
JPL Research and Technology Development FundUNSPECIFIED
Canadian Institute for Theoretical AstrophysicsUNSPECIFIED
Dunlap Institute for Astronomy and AstrophysicsUNSPECIFIED
University of TorontoUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/P000649/1
Research Council of Norway251328
Research Council of Norway274990
European Research Council (ERC)819478
University of MiamiUNSPECIFIED
Robert A. Millikan FellowshipUNSPECIFIED
Swiss National Science Foundation (SNSF)PZ00P2_179934
New York University (NYU)UNSPECIFIED
Subject Keywords:Cosmological evolution; CO line emission; High-redshift galaxies; Molecular gas; Radio astronomy
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Cosmological evolution (336); CO line emission (262); High-redshift galaxies (734); Molecular gas (1073); Radio astronomy (1338)
Record Number:CaltechAUTHORS:20220722-769226000
Persistent URL:
Official Citation:Marie K. Foss et al 2022 ApJ 933 184
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115788
Deposited By: George Porter
Deposited On:26 Jul 2022 17:56
Last Modified:26 Jul 2022 17:56

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