An Intensity Mapping Detection of Aggregate CO Line Emission at 3 mm

Garrett K. Keating; Daniel P. Marrone; Geoffrey C. Bower; Ryan P. Keenan

doi:10.3847/1538-4357/abb08e

paper

An Intensity Mapping Detection of Aggregate CO Line Emission at 3 mm

arXiv:2008.08087 · doi:10.3847/1538-4357/abb08e

Abstract

We present a detection of molecular gas emission at $z \sim 1 - 5$ using the technique of line intensity mapping. We make use of a pair of 3 mm interferometric data sets, the first from the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field (ASPECS), and the second from a series of Atacama Compact Array (ACA) observations conducted between 2016 and 2018, targeting the COSMOS field. At 100 GHz, we measure non-zero power at 97.8% and 99.9% confidence in the ACA and ALMA data sets, respectively. In the joint result, we reject the zero-power hypothesis at 99.99% confidence, finding $I ~_{s}^{2} (ν) = 770 \pm 210 μ K^{2} Hz sr$ . After accounting for sample variance effects, the estimated spectral shot power is $I ~_{s}^{2} (ν) = 101 0_{- 390}^{+ 550} μ K^{2} Hz sr$ . We derive a model for the various line species our measurement is expected to be sensitive to, and estimate the shot power to be $12 0_{- 40}^{+ 80} μ K^{2} h^{- 3} Mpc^{3}$ , $20 0_{- 70}^{+ 120} μ K^{2} h^{- 3} Mpc^{3}$ , and $9 0_{- 40}^{+ 70} μ K^{2} h^{- 3} Mpc^{3}$ for CO(2-1) at $z = 1.3$ , CO(3-2) at $z = 2.5$ , and CO(4-3) at $z = 3.6$ , respectively. Using line ratios appropriate for high-redshift galaxies, we find these results to be in good agreement with those from the CO Power Spectrum Survey (COPSS). Adopting $α_{CO} = 3.6 M_{⊙} (K km s^{- 1} pc^{2})^{- 1}$ , we estimate a cosmic molecular gas density of $ρ_{H_{2}} (z) \sim 1 0^{8} M_{⊙} Mpc^{- 3}$ between $z = 1 - 3$ .

25 pages, 12 figures, 6 tables, 2 appendices. Accepted for publication in ApJ

An Intensity Mapping Detection of Aggregate CO Line Emission at 3 mm

Abstract

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