The impact of large-scale galaxy clustering on the variance of the Hellings-Downs correlation: theoretical framework

Abstract

While pulsar timing array experiments have recently found evidence for the existence of a stochastic gravitational wave (GW) background, its origin is still unclear. If this background is of astrophysical origin, we expect the distribution of GW sources to follow the one of galaxies. Since galaxies are not perfectly isotropically distributed at large scales, but follow the cosmological large-scale structure, this would lead to an intrinsic anisotropy in the distribution of GW sources. In this work, we develop a formalism to account for this anisotropy, by considering a Gaussian ensemble of sources in each realization of the universe and then taking ensemble averages over all such realizations. We find that large-scale galaxy clustering has no impact on the expectation value of pulsar timing residual correlations, described by the Hellings-Downs curve. However, it introduces a new contribution to the variance of the Hellings-Downs correlation. Hence, the anisotropic distribution of sources contributes to the amount by which the measurements of pulsar timing residual correlations, in our single realization of the universe, may differ from the Hellings-Downs curve.

13 pages

References in corpus (20)

• The NANOGrav 15-year Data Set: Evidence for a Gravitational-Wave Background
• Search for an isotropic gravitational-wave background with the Parkes Pulsar Timing Array
• Searching for the nano-Hertz stochastic gravitational wave background with the Chinese Pulsar Timing Array Data Release I
• The NANOGrav 15-year Data Set: Search for Signals from New Physics
• The Cosmic Linear Anisotropy Solving System (CLASS) I: Overview
• Cosmic microwave background limits on accreting primordial black holes
• The second data release from the European Pulsar Timing Array I. The dataset and timing analysis
• The Clustering of the SDSS Main Galaxy Sample II: Mock galaxy catalogues and a measurement of the growth of structure from Redshift Space Distortions at $z=0.15$
• Inflationary interpretation of the stochastic gravitational wave background signal detected by pulsar timing array experiments
• Mapping gravitational-wave backgrounds using methods from CMB analysis: Application to pulsar timing arrays
• Searching For Gravitational Waves From Cosmological Phase Transitions With The NANOGrav 12.5-year dataset
• Variance of the Hellings-Downs Correlation
• Hellings and Downs correlation of an arbitrary set of pulsars
• Pulsar and cosmic variances of pulsar timing-array correlation measurements of the stochastic gravitational wave background
• The effect of small inter-pulsar distance variations in stochastic gravitational wave background searches with Pulsar Timing Arrays
• Answers to frequently asked questions about the pulsar timing array Hellings and Downs curve
• A Test of Gravity with Pulsar Timing Arrays
• Source anisotropies and pulsar timing arrays
• Pulsar timing array source ensembles
• The impact of large-scale galaxy clustering on the variance of the Hellings-Downs correlation: numerical results

Cited by in corpus (5)

• Measuring anisotropies in the PTA band with cross-correlations
• Mitigating cosmic variance in the Hellings-Downs curve: a Cosmic Microwave Background analogy
• Dissecting the nanoHz gravitational wave sky: frequency-correlated anisotropy induced by eccentric supermassive black hole binaries
• The impact of large-scale galaxy clustering on the variance of the Hellings-Downs correlation: numerical results
• Anisotropy of Nanohertz Gravitational Wave Background and Source Clustering from Supermassive Binary Black Holes Based on Cosmological Simulation