COMAP Early Science: I. Overview
  The CO Mapping Array Project (COMAP) aims to use line intensity mapping of
carbon monoxide (CO) to trace the distribution and global properties of
galaxies over cosmic time, back to the Epoch of Reionization (EoR). To validate
the technologies and techniques needed for this goal, a Pathfinder instrument
has been constructed and fielded. Sensitive to CO(1-0) emission from
$z=2.4$-$3.4$ and a fainter contribution from CO(2-1) at $z=6$-8, the
Pathfinder is surveying $12$ deg$^2$ in a 5-year observing campaign to detect
the CO signal from $z\sim3$. Using data from the first 13 months of observing,
we estimate $P_\mathrm{CO}(k) = -2.7 \pm 1.7 \times 10^4\mu\mathrm{K}^2
\mathrm{Mpc}^3$ on scales $k=0.051-0.62 \mathrm{Mpc}^{-1}$ - the first direct
3D constraint on the clustering component of the CO(1-0) power spectrum. Based
on these observations alone, we obtain a constraint on the amplitude of the
clustering component (the squared mean CO line temperature-bias product) of
$\langle Tb\rangle^2<49$ $\mu$K$^2$ - nearly an order-of-magnitude improvement
on the previous best measurement. These constraints allow us to rule out two
models from the literature. We forecast a detection of the power spectrum after
5 years with signal-to-noise ratio (S/N) 9-17. Cross-correlation with an
overlapping galaxy survey will yield a detection of the CO-galaxy power
spectrum with S/N of 19. We are also conducting a 30 GHz survey of the Galactic
plane and present a preliminary map. Looking to the future of COMAP, we examine
the prospects for future phases of the experiment to detect and characterize
the CO signal from the EoR.
