The CO Mapping Array Pathfinder (COMAP) uses spectrographic observations to trace carbon monoxide atoms in the very early universe—within about three billion years of the Big Bang, a time of intense star formation responsible for the creation of about half of the stars in existence today.
A different way to use spectra
COMAP employs a technique called line-intensity mapping, which focuses on isolating spectral lines that serve as markers for certain molecules thought to be abundant during the early Universe. Line-intensity mapping covers a larger area of the sky than typical observations, enabling researchers to trace the gas clouds that provide fodder for star formation, as opposed to standard methods of spectroscopy, which capture an entire spectrum from a single object such as a supernova, in order to determine its makeup. By not targeting individual objects, line-intensity mapping provides statistical information about all types of objects, both faint and bright, emitting in these molecular lines. This provides clues about the global connections between molecular gas and various astrophysical processes like star formation.
COMAP targets carbon monoxide, which correlates well with the massive primordial clouds of hydrogen fueling star-formation. COMAP's initial phase began in the summer of 2019 with a single 19-pixel receiver mounted on a 10-meter dish at the Owens Valley Radio Observatory that is tracing galaxies at a redshift of 3 via the CO(1-0) line, which shows carbon monoxide atoms dropping into their lowest energy states.
This first phase already provides significant challenges in terms of distinguishing the signal from foreground contamination and in systematics, as the signal is six orders of magnitude below what we see from the cosmic microwave background! Future phases should tackle the even more challenging signal—at redshift 6 and above—from the Epoch of Reionization, when the first giant stars and new galaxies began to heat up cold interstellar gas, making the Universe glow once more.
COMAP is a collaboration involving several institutions, including Caltech, Stanford, JPL, Berkeley, Princeton, the University of Manchester, the University of Maryland, the University of Miami, the University of Oslo, and the University of Toronto. KIPAC members have made key contributions to the theoretical motivation as well as the instrumentation.