COMAP Early Science: III. CO Data Processing

Abstract

We describe the first season COMAP analysis pipeline that converts raw detector readouts to calibrated sky maps. This pipeline implements four main steps: gain calibration, filtering, data selection, and map-making. 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 ${\chi }^2$ and multi-scale correlation tests. Applying this pipeline to the first-season COMAP data, we produce a dataset 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.

Paper 3 of 7 in series. 26 pages, 23 figures, submitted to ApJ

References in corpus (20)

• Possibility of Precise Measurement of the Cosmological Power Spectrum With a Dedicated 21cm Survey After Reionization
• Line-Intensity Mapping: 2017 Status Report
• The HETDEX Instrumentation: Hobby-Eberly Telescope Wide Field Upgrade and VIRUS
• The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) Survey Design, Reductions, and Detections
• Carbon monoxide line emission as a CMB foreground: tomography of the star-forming universe with different spectral resolutions
• Cross-correlations as a cosmological carbon monoxide detector
• Carbon Monoxide Intensity Mapping at Moderate Redshifts
• An Intensity Mapping Detection of Aggregate CO Line Emission at 3 mm
• COMAP Early Science: I. Overview
• An empirical representation of a physical model for the ISM [CII], CO, and [CI] emission at redshift $1\le z\le 9$
• Astrophysics and Cosmology with Line-Intensity Mapping
• COMAP Early Science: V. Constraints and Forecasts at $z\sim 3$
• Precision Tests of CO and [CII] Power Spectra Models against Simulated Intensity Maps
• An Intensity Mapping Constraint on the CO-Galaxy Cross Power Spectrum at Redshift ~ 3
• COMAP Early Science: IV. Power Spectrum Methodology and Results
• A model of spectral line broadening in signal forecasts for line-intensity mapping experiments
• COMAP Early Science: II. Pathfinder Instrument
• COMAP Early Science: VI. A First Look at the COMAP Galactic Plane Survey
• On estimation of contamination from hydrogen cyanide in carbon monoxide line intensity mapping
• Synergies between the COMAP CO Line Intensity Mapping mission and a Lyα galaxy survey: How to probe the early universe with voxel based analysis of observational data

Cited by in corpus (13)

• COMAP Early Science: I. Overview
• COMAP Early Science: V. Constraints and Forecasts at $z\sim 3$
• COMAP Early Science: VII. Prospects for CO Intensity Mapping at Reionization
• COMAP Early Science: IV. Power Spectrum Methodology and Results
• COMAP Early Science: II. Pathfinder Instrument
• COMAP Early Science: VI. A First Look at the COMAP Galactic Plane Survey
• Forecasts and Statistical Insights for Line Intensity Mapping Cross-Correlations: A Case Study with 21cm x [CII]
• The deconvolved distribution estimator: enhancing reionisation-era CO line-intensity mapping analyses with a cross-correlation analogue for one-point statistics
• COMAP Pathfinder -- Season 2 results I. Improved data selection and processing
• Boosting Line Intensity Map Signal-to-Noise with the Ly-$\alpha$ Forest Cross-Correlation
• COMAP Pathfinder -- Season 2 results II. Updated constraints on the CO(1-0) power spectrum
• COMAP Pathfinder -- Season 2 results III. Implications for cosmic molecular gas content at "Cosmic Half-past Eleven"
• Direct correlation of line intensity mapping and CMB lensing from evolution along the lightcone