COMAP Early Science: II. Pathfinder Instrument

TL;DR

The COMAP Pathfinder demonstrates the feasibility of line intensity mapping for detecting faint CO signals from high redshift galaxies, providing early science results and guiding future instrument development.

Contribution

This paper presents the design, construction, and initial results of the COMAP Pathfinder, a novel instrument for CO line intensity mapping at high redshift.

Findings

First-year data yields useful science results.

Instrument design successfully meets LIM requirements.

Experience informs future experiment development.

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 (COMAP) 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 $z\sim3$. 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 drive the design of the next generations of experiments.