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The NANOGrav Nine-year Data Set: Limits on the Isotropic Stochastic Gravitational Wave Background

Arzoumanian, Z. and Mingarelli, C. M. F. (2016) The NANOGrav Nine-year Data Set: Limits on the Isotropic Stochastic Gravitational Wave Background. Astrophysical Journal, 821 (1). p. 13. ISSN 0004-637X.

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We compute upper limits on the nanohertz-frequency isotropic stochastic gravitational wave background (GWB) using the 9 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration. Well-tested Bayesian techniques are used to set upper limits on the dimensionless strain amplitude (at a frequency of 1 yr^(−1) for a GWB from supermassive black hole binaries of A_(gw) < 1.5 x 10^(-15). We also parameterize the GWB spectrum with a broken power-law model by placing priors on the strain amplitude derived from simulations of Sesana and McWilliams et al. Using Bayesian model selection we find that the data favor a broken power law to a pure power law with odds ratios of 2.2 and 22 to one for the Sesana and McWilliams prior models, respectively. Using the broken power-law analysis we construct posterior distributions on environmental factors that drive the binary to the GW-driven regime including the stellar mass density for stellar-scattering, mass accretion rate for circumbinary disk interaction, and orbital eccentricity for eccentric binaries, marking the first time that the shape of the GWB spectrum has been used to make astrophysical inferences. Returning to a power-law model, we place stringent limits on the energy density of relic GWs, Ω_(gw)(f)h^2 < 4.2 x 10^(-10). Our limit on the cosmic string GWB, Ω_(gw)(f)h^2 < 2.2 x 10^(-10), translates to a conservative limit on the cosmic string tension with Gµ < 3.3 x 10^(-8), a factor of four better than the joint Planck and high-l cosmic microwave background data from other experiments.

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Mingarelli, C. M. F.0000-0002-4307-1322
Additional Information:© 2016. The American Astronomical Society. Received 2015 October 5; accepted 2016 February 18; published 2016 April 4. We would like to thank David Merritt for his useful comments on the manuscript. The NANOGrav project receives support from National Science Foundation (NSF) PIRE program award number 0968296 and NSF Physics Frontier Center award number 1430284. NANOGrav research at UBC is supported by an NSERC Discovery Grant and Discovery Accelerator Supplement and by the Canadian Institute for Advanced Research. D.R.M. acknowledges partial support through the New York Space Grant Consortium. M.V. acknowledges support from the JPL RTD program. Portions of this research were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. C.M.F.M. was supported by a Marie Curie International Outgoing Fellowship within the 7th European Community Framework Programme. S.R.T. was supported by appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by Oak Ridge Associated Universities through a contract with NASA. J.A.E. and Rv.H. acknowledge support by NASA through Einstein Fellowship grants PF4-150120 and PF3-140116, respectively. S.A.S. acknowledges funding from an NWO Vidi fellowship (PI: JTW Hessels). A.S. is supported by a University Research Fellowship of the Royal Society. Y.W. is supported by the National Science Foundation of China (NSFC) under grant NO. 11503007. This work was supported in part by National Science Foundation Grant No. PHYS-1066293 and by the hospitality of the Aspen Center for Physics. This research was performed in part using the Zwicky computer cluster at Caltech supported by NSF under MRI-R2 award no. PHY-0960291 and by the Sherman Fairchild Foundation. A majority of the computational work was performed on the Nemo cluster at UWM supported by NSF grant No. 0923409. Parts of the analysis in this work were carried out on the Nimrod cluster made available by S.M.R. Data for this project were collected using the facilities of the National Radio Astronomy Observatory and the Arecibo Observatory. The National Radio Astronomy Observatory is a facility of the NSF operated under cooperative agreement by Associated Universities, Inc. The Arecibo Observatory is operated by SRI International under a cooperative agreement with the NSF (AST-1100968), and in alliance with Ana G. Méndez-Universidad Metropolitana and the Universities Space Research Association.
Funding AgencyGrant Number
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Canadian Institute for Advanced Research (CIAR)UNSPECIFIED
New York Space Grant ConsortiumUNSPECIFIED
JPL Research and Technology Development FundUNSPECIFIED
Marie Curie FellowshipUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
NASA Einstein FellowshipPF4-150120
NASA Einstein FellowshipPF3-140116
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
National Science Foundation of China11503007
Sherman Fairchild FoundationUNSPECIFIED
Subject Keywords:gravitational waves; methods: data analysis; pulsars: general
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Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2016-33
Issue or Number:1
Record Number:CaltechAUTHORS:20160509-120030347
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Official Citation:Z. Arzoumanian et al 2016 ApJ 821 13
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66774
Deposited By: Ruth Sustaita
Deposited On:09 May 2016 20:21
Last Modified:09 Mar 2020 13:19

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