COMAP Early Science. II. Pathfinder Instrument

Abstract

Line intensity mapping (LIM) is a new technique for tracing the global properties of galaxies over cosmic time. Detection of the very faint signals from redshifted carbon monoxide (CO), a tracer of star formation, pushes the limits of what is feasible with a total-power instrument. The CO Mapping Project Pathfinder is a first-generation instrument aiming to prove the concept and develop the technology for future experiments, as well as delivering early science products. With 19 receiver channels in a hexagonal focal plane arrangement on a 10.4 m antenna and an instantaneous 26–34 GHz frequency range with 2 MHz resolution, it is ideally suited to measuring CO (J = 1–0) from z ∼ 3. In this paper we discuss strategies for designing and building the Pathfinder and the challenges that were encountered. The design of the instrument prioritized LIM requirements over those of ancillary science. After a couple of years of operation, the instrument is well understood, and the first year of data is already yielding useful science results. Experience with this Pathfinder will guide the design of the next generations of experiments.

COMAP Early Science. IV. Power Spectrum Methodology and Results

“…For now, we assume the beam to be both achromatic (i.e., constant in frequency) and azimuthally symmetric. We construct an azimuthally symmetric beam model by averaging the full 2D (azimuth-elevation) beam model (Lamb et al 2022) and inserting an exponential cutoff at around 30′.…”

“…This paper, one of a set associated with the first-season COMAP analysis, presents the methodology used to constrain the CO power spectrum with COMAP data. An overview of the COMAP experiment is presented by Cleary et al (2022), while the COMAP instrument is described by Lamb et al (2022).…”

“…As described by Lamb et al (2022) and Foss et al (2022), the COMAP focal plane consists of 19 different feed horns, arranged in a hexagonal pattern, with about 12′ sky separation between the closest feeds. The signal entering each feed horn is sent through its own signal chain, with its own amplifiers and digital high-resolution spectrometers.…”

COMAP Early Science. VI. A First Look at the COMAP Galactic Plane Survey

“…Observations for the COMAP Galactic Plane Survey were made using the COMAP Pathfinder telescope (Lamb et al 2022), sited in Owens Valley Radio Observatory (OVRO) in California. The telescope itself is of Cassegrain design and has an FWHM beamwidth of 4 5 consistent to ±4% across 26-34 GHz (Lamb et al 2022). The Pathfinder has a focal plane array of 19 forward-facing pixels in a hexagonal pattern.…”

COMAP Early Science. V. Constraints and Forecasts at z ∼ 3

“…COMAP Pathfinder observations at 26-34 GHz measure CO (1-0) (rest frequency 115.27 GHz) at z = 2.4-3.4 in three fields of 4 deg 2 , allowing characterization of larger transverse scales than with previous interferometric LIM surveys. Other papers associated with these results 17 describe the instrument (Lamb et al 2022), data processing and mapmaking procedures (Foss et al 2022), and power spectrum methodology and results (Ihle et al 2022). This paper aims to convert these measurements into astrophysical inferences and consider forecasts for the remainder of the initial 5 yr Pathfinder campaign, with a separate paper by Breysse et al (2022a) considering potential realizations of COMAP beyond the Pathfinder.…”