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COPSS II: The Molecular Gas Content of Ten Million Cubic Megaparsecs at Redshift z ~ 3

Keating, Garrett K. and Marrone, Daniel P. and Bower, Geoffrey C. and Leitch, Erik and Carlstrom, John E. and DeBoer, David R. (2016) COPSS II: The Molecular Gas Content of Ten Million Cubic Megaparsecs at Redshift z ~ 3. Astrophysical Journal, 830 (1). Art. No. 34. ISSN 0004-637X.

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We present a measurement of the abundance of carbon monoxide in the early universe, utilizing the final results from the CO Power Spectrum Survey (COPSS). Between 2013 and 2015, we performed observations with the Sunyaev–Zel'dovich Array to measure aggregate CO emission from z ~ 3 galaxies with the intensity mapping technique. Data were collected on 19 fields, covering an area of 0.7 square degrees, over the frequency range 27-35 GHz. With these data, along with data analyzed in COPSS I, we are able to observe the CO(1–0) transition within the redshift range z = 2.3-3.3 for spatial frequencies between k=0.5-10 h Mpc}^(-1), spanning a comoving volume of 4.9 x 10^6 h^(-3) Mpc^(-3). We present estimates of contributions from continuum sources and ground illumination within our measurement. We constrain the amplitude of the CO power spectrum to P_(CO) = 3.0_(-1.3)^(+1.3) x 10^3 µK^2 (h^(-1) Mpc)^3, or Δ_(CO)^2 (k =1 h Mpc^(-1)) = 1.5_(-0.7}^(+0.7)} x 10^3 µK^2, at 68% confidence, and P_(CO) > 0 at 98.9% confidence. These results are a factor of 10 improvement in sensitivity compared to those of COPSS I. With this measurement, we constrain on the CO(1–0) galaxy luminosity function at z ~ 3. Assuming that CO emission is proportional to halo mass and using theoretical estimates of the scatter in this relationship, we constrain the ratio of CO(1-0) luminosity to halo mass to A_(CO) = 6.3_(-2.1)^(+1.4) x 10^(-7), L_⊙M_⊙^(-1). Assuming a Milky Way-like linear relationship between CO luminosity and molecular gas mass, we estimate a mass fraction of molecular gas of f_(H_2) = 5.5_(-2.2)^(+3.4) x 10^(-2) for halos with masses of ~10^(12) M_⊙. Using theoretical estimates for the scaling of molecular gas mass fraction and halo mass, we estimate the cosmic molecular gas density to be ρ_(z ~ 3)(H_2) = 1.1_(-0.4)^(+0.7) x 10^8 M_⊙ Mpc^(-3).

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Additional Information:© 2016. The American Astronomical Society. Received 2016 May 11; revised 2016 July 10; accepted 2016 July 25; published 2016 October 7. The authors would like to thank the referee for the thoughtful and timely feedback, which helped improve the quality and clarity of this manuscript. We thank D. Hawkins, J. Lamb, D. Woody, and S. Muchovej for their technical support. We would also like to thank C. Heiles, R. Plambeck, T-C. Chang, T. Li, and G. Popping for useful discussions and thoughtful feedback. We gratefully acknowledge the James S. McDonnell Foundation, the National Science Foundation (NSF), and the University of Chicago for funding to construct the SZA. Partial support was provided by NSF Physics Frontier Center grant PHY-0114422 to the Kavli Institute of Cosmological Physics at the University of Chicago. Support for CARMA construction was derived from the states of California, Illinois, and Maryland, the James S McDonnell Foundation, the Gordon and Betty Moore Foundation, the Kenneth T and Eileen L Norris Foundation, the University of Chicago, the Associates of the California Institute of Technology, and the National Science Foundation. Support for CARMA operations and analysis was provided in part by the National Science Foundation University Radio Observatories Program, including awards AST-1140019 (to the University of Chicago), AST-1140031 (University of California-Berkeley), AST-1140021 (California Institute of Technology), and by the CARMA partner universities.
Funding AgencyGrant Number
James S. McDonnell FoundationUNSPECIFIED
University of ChicagoUNSPECIFIED
State of CaliforniaUNSPECIFIED
State of IllinoisUNSPECIFIED
State of MarylandUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Kenneth T. and Eileen L. Norris FoundationUNSPECIFIED
Associates of the California Institute of TechnologyUNSPECIFIED
CARMA partner universitiesUNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: high-redshift; ISM: molecules; methods: statistical
Record Number:CaltechAUTHORS:20161117-133957434
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Official Citation:Garrett K. Keating et al 2016 ApJ 830 34
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:72137
Deposited By: George Porter
Deposited On:17 Nov 2016 22:06
Last Modified:17 Nov 2016 22:06

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