http://arxiv.org/abs/1702.02180
Pulsar Timing Arrays (PTA) around the world are using the incredible consistency of millisecond pulsars to measure low frequency gravitational waves from (super)Massive Black Hole (MBH) binaries. We use comprehensive MBH merger models based on cosmological hydrodynamic simulations to predict the spectra of a stochastic Gravitational-Wave Background (GWB). We use real Time-of-Arrival (TOA) specifications from the European, NANOGrav, Parkes, and International PTA (IPTA) to calculate realistic times to detection of the GWB across a wide range of model parameters. In addition to exploring the parameter space of environmental hardening rates (in particular: stellar scattering efficiencies), we have expanded our models to include eccentric binary evolution which can have a strong effect on the GWB spectrum. Our models show that strong stellar scattering and high characteristic eccentricities lead to higher GWB amplitudes and easier detections. While the GWB amplitude is degenerate between cosmological and environmental parameters, the location of a spectral turnover at low frequencies ($f \lesssim 0.1 \, \mathrm{yr}^{-1}$) is strongly indicative of environmental coupling. At high frequencies ($f\gtrsim 1 \, \mathrm{yr}^{-1}$), the GWB spectral index can be used to infer the number density of sources and possibly their eccentricity distribution. Even with pessimistic merger models, if the current rate of PTA expansion continues, we find that the International PTA (IPTA) is highly likely to make a detection within 10–15 years.
L. Kelley, L. Blecha, L. Hernquist, et. al.
Thu, 9 Feb 17
23/67
Comments: 16 pages, 1 table, 15 figures; comments welcomed