The NANOGrav 11 Year Data Set: Pulsar-timing Constraints on the Stochastic Gravitational-wave Background

By Z. Arzoumanian, P. Baker, A. Brazier, S. Burke-Spolaor, S. Chamberlin, S. Chatterjee, B. Christy, J. Cordes, N. Cornish, F. Crawford and 51 more. 2018

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We search for an isotropic stochastic gravitational-wave background (GWB) in the newly released 11 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). While we find no evidence for a GWB, we place constraints on a population of inspiraling supermassive black hole (SMBH) binaries, a network of decaying cosmic strings, and a primordial GWB. For the first time, we find that the GWB constraints are sensitive to the solar system ephemeris (SSE) model used and that SSE errors can mimic a GWB signal. We developed an approach that bridges systematic SSE differences, producing the first pulsar-timing array (PTA) constraints that are robust against SSE errors. We thus place a 95% upper limit on the GW-strain amplitude of AGWB < 1.45 × 10−15 at a frequency of f = 1 yr−1 for a fiducial f−2/3 power-law spectrum and with interpulsar correlations modeled. This is a factor of ∼2 improvement over the NANOGrav nine-year limit calculated using the same procedure. Previous PTA upper limits on the GWB (as well as their astrophysical and cosmological interpretations) will need revision in light of SSE systematic errors. We use our constraints to characterize the combined influence on the GWB of the stellar mass density in galactic cores, the eccentricity of SMBH binaries, and SMBH–galactic-bulge scaling relationships. We constrain the cosmic-string tension using recent simulations, yielding an SSE-marginalized 95% upper limit of Gμ < 5.3 × 10−11—a factor of ∼2 better than the published NANOGrav nine-year constraints. Our SSE-marginalized 95% upper limit on the energy density of a primordial GWB (for a radiation-dominated post-inflation universe) is ΩGWB(f) h2 < 3.4 × 10−10.

Subfields: Astronomy and Astrophysics, Oceanography

View Paper: https://www.semanticscholar.org/paper/e879ff1a3a23a57cc44339b0276a05919e39e901

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Citations in the corpus

Beyond the Standard Models with cosmic strings (2019, methodology): “probed by CMB, 21 cm, and lensing observables, see app.Afor more details on non-GW probes. The strongest constraints come from pulsar timing array EPTA, G. 8 10 10 [119], and NANOGrav, G. 5:3 10 11 [120]. Comparison with the theoretical predictions from the SGWB from cosmic strings leads to G. 2 10 ”
The NANOGrav 11-year Data Set: High-precision Timing of 45 Millisecond Pulsars (2017, methodology): “As with previously released data sets, the data described in this paper are being used to constrain the presence of gravitational waves due to a stochastic background of supermassive black hole binaries (Arzoumanian et al. 2018).”
The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background (2023, background): “Uncertainties in the Jovian orbit impacted NANOGrav’s 11-year GWB search (Arzoumanian et al. 2018; Vallisneri et al. 2020), but they are now negligible.”
Solar-mass primordial black holes explain NANOGrav hint of gravitational waves (2020, background): “The previous PTA constraints are shown by shaded regions: EPTA [28], NANOGrav 11-yr [24], and PPTA [25].”
The NANOGrav 15 yr Data Set: Constraints on Supermassive Black Hole Binaries from the Gravitational-wave Background (2023, methodology): “Subsequent work showed the importance of analyzing many pulsars and accounting for their red noise and systematic errors in solar system ephemerides when establishing PTA upper limits (Arzoumanian et al. 2018; Hazboun et al. 2020; Vallisneri et al. 2020; Johnson et al. 2022).”
Semianalytic calculation of gravitational wave spectrum nonlinearly induced from primordial curvature perturbations (2018, background): “n from the RD era in the case of power-law curvature perturbations with A = 10 12, n s = 2, and k = 0:05Mpc 1. The blue lines denote existing pulsar timing array constraints from EPTA [53], NANOGrav [54], and PPTA [55]. The pink lines show sensitivity curves [56] of various future GW observations re”
Primordial black holes and gravitational waves from parametric amplification of curvature perturbations (2019, methodology): “ectrum of induced GWs with the parameter set 2(blue), set 3(green), set 4(purple) in Tab.1. We compare them with the constrain or the sensitivity curves of GW detectors including EPTA [100], NANOGrav [101], PPTA [102], SKA [103], LISA [104], Taiji [105], DECIGO [106], BBO [107], KAGRA [108], aLIGO [”