First Results from COPSS: The CO Power Spectrum Survey
We present constraints on the abundance of carbon monoxide in the early universe from the CO Power Spectrum Survey. We utilize a data set collected between 2005 and 2008 using the Sunyaev–Zel'dovich Array (SZA), which was previously used to measure arcminute-scale fluctuations of the cosmic microwave background. This data set features observations of 44 fields, covering an effective area of 1.7 square degrees, over a frequency range of 27–35 GHz. Using the technique of intensity mapping, we are able to probe the CO(1–0) transition, with sensitivity to spatial modes between k = 0.5–2 h Mpc^(−1) over a range in redshift of z = 2.3–3.3, spanning a comoving volume of 3.6 × 10^6 h^(−3) Mpc^3. We demonstrate our ability to mitigate foregrounds, and present estimates of the impact of continuum sources on our measurement. We constrain the CO power spectrum to P_(CO) < 2.6 × 10^4 μK^2 (h^(−1) Mpc)^3, or Δ^2_(CO)(k = 1 h Mpc^(−1)) < 1.3 × 10^3 μK^2, at 95% confidence. This limit resides near optimistic predictions for the CO power spectrum. Under the assumption that CO emission is proportional to halo mass during bursts of active star formation, this corresponds to a limit on the ratio of CO(1–0) luminosity to host halo mass of A_(CO) < 1.2 × 10^(−5) L⊙_ M_⊙^(−1). Further assuming a Milky Way-like conversion factor between CO luminosity and molecular gas mass (α_(CO) = 4.3 M_⊙ (K km s^(−1) pc^(−2))^(−1)), we constrain the global density of molecular gas to ρ_(z~3) (M_H_2) ⩽ 2.8 x 10^8 M_☉ Mpc^(-3).
© 2015 American Astronomical Society. Received 2015 August 25; accepted 2015 October 22; published 2015 November 30. The authors would like to thank F. M. Fornasini and R. L. Plambeck for their valuable feedback during the preparation of this manuscript. This work was supported in part by the National Science Foundation University Radio Observatories Program, AST-1140031. We gratefully acknowledge the James S. McDonnell Foundation, the National Science Foundation, and the University of Chicago for funding to construct the SZA. The operation of the SZA was supported by NSF through award AST-0604982. Partial support was provided by NSF Physics Frontier Center grant PHY-0114422 to the Kavli Institute of Cosmological Physics at the University of Chicago, and by NSF grants AST-0507545 and AST-0507161 to Columbia University.
Submitted - 1510.06744v1.pdf
Published - apj_814_2_140.pdf