Development of a 12-20 GHz CO Intensity Mapping Receiver for Capturing the Star-formation History in the Early Universe

Line-intensity mapping (LIM) is an emerging observational technique that measures the aggregate spectral emission from molecules and atoms in galaxies and the intergalactic medium. By targeting redshifted emission lines, LIM experiments uniquely probe the large-scale matter distribution in the early universe, extending observational reach back to the epoch of reionization (EoR).

The Carbon Monoxide Mapping Array Project (COMAP) aims to detect CO emission from galaxies at redshifts z > 2.4. Unlike the 21 cm line of neutral hydrogen, which traces diffuse gas, CO emission is strongly correlated with star-formation activity, providing a complementary probe of galaxy evolution. The COMAP Pathfinder has been observing selected fields since 2019 in the 26–34 GHz band (z = 2.4–3.4). Its receiver employs a 19-feed array to increase survey speed and uses cryogenic HEMT amplifiers to achieve low system noise temperatures.

The COMAP-EoR receiver, which will target the 12–20 GHz band corresponding to z = 4.8–8.6, is currently under development. Before constructing the full 19-feed array, our group is building a 4-feed prototype receiver to assess system feasibility and characterize potential systematics. This development includes optimizing waveguide components such as the feedhorn and polarizer, configuring the frequency downconversion chain, and integrating the receiver with the analog-to-digital converters and data acquisition system. The prototype receiver will be deployed on the Taeduk Radio Astronomy Observatory (TRAO) 13.7 m dish to conduct complementary observations to the COMAP Pathfinder.