Upper limits on persistent gravitational waves using folded data and the full covariance matrix from Advanced LIGO${}^{\prime }$s first two observing runs

Abstract

The stochastic gravitational-wave background (SGWB) created by astrophysical sources in the nearby Universe is likely to be anisotropic. Upper limits on SGWB anisotropy have been produced for all major data-taking runs by the ground-based laser interferometric detectors. However, due to the challenges involved in numerically inverting the pixel-to-pixel noise covariance matrix, which is necessary for setting upper limits, the searches accounted for angular correlations in the map by using the spherical harmonic basis, where regularization was relatively easier. This approach is better suited though for extended sources. Moreover, the upper-limit maps produced in the two different bases are seemingly different. While the upper limits may be consistent within statistical errors, it was important to check whether the results would remain consistent if the full noise covariance matrix was used in the pixel basis. Here, we use the full pixel- to-pixel Fisher information matrix to create upper-limit maps of SGWB anisotropy. We first perform an unmodeled search for persistent, directional gravitational-wave sources using folded data from the first (O1) and second (O2) observing runs of Advanced LIGO and show that the results are consistent with the upper limits published by the LIGO-Virgo Collaboration (LVC). We then explore various ways to account for the pixel-to-pixel Fisher information matrix using singular-value decomposition and Bayesian regularization schemes. We do not find evidence for any SGWB signal in the data and the upper limits are consistent with the LVC results within statistical errors. Through an injection study, we show that they are all valid 95\% upper limits, that is, the upper limit in a pixel is less than the injected signal strength in less than 5\% of the pixels.

arXiv comment18 pages, 7 figures, published version with a revised figure and clarified main text, results unchanged, typos and grammatical corrections

References in corpus (34)

• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• Gravitational Wave Experiments and Early Universe Cosmology
• Physics, Astrophysics and Cosmology with Gravitational Waves
• Detecting a stochastic background of gravitational radiation: Signal processing strategies and sensitivities
• Detection methods for stochastic gravitational-wave backgrounds: a unified treatment
• CMasher: Scientific colormaps for making accessible, informative and 'cmashing' plots
• Search for the isotropic stochastic background using data from Advanced LIGO's second observing run
• Particle production during inflation and gravitational waves detectable by ground-based interferometers
• The astrophysical gravitational wave stochastic background
• Directional limits on persistent gravitational waves from Advanced LIGO's first observing run
• Anisotropy of the astrophysical gravitational wave background: analytic expression of the angular power spectrum and correlation with cosmological observations
• Anisotropies of Gravitational Wave Backgrounds: A Line Of Sight Approach
• Probing the anisotropies of a stochastic gravitational-wave background using a network of ground-based laser interferometers
• Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo's first three observing runs
• Directional limits on persistent gravitational waves using LIGO S5 science data
• A radiometer for stochastic gravitational waves
• Anisotropies in the stochastic gravitational-wave background: Formalism and the cosmic string case
• Measurement of Parity Violation in the Early Universe using Gravitational-wave Detectors
• Peccei-Quinn Phase Transition at LIGO
• Gravitational wave radiometry: Mapping a stochastic gravitational wave background
• Astrophysical Sources of Stochastic Gravitational-Wave Background
• Directional limits on persistent gravitational waves using data from Advanced LIGO's first two observing runs
• Limits on Direct Detection of Gravitational Waves
• Improved limits on a stochastic gravitational-wave background and its anisotropies from Advanced LIGO O1 and O2 runs
• Very fast stochastic gravitational wave background map making using folded data
• Fast Gravitational Wave Radiometry using Data Folding
• Gravitational Wave Background Sky Maps from Advanced LIGO O1 Data
• Treatment of Calibration Uncertainty in Multi-Baseline Cross-Correlation Searches for Gravitational Waves
• Multibaseline gravitational wave radiometry
• Unified mapmaking for an anisotropic stochastic gravitational wave background
• All-sky radiometer for narrowband gravitational waves using folded data
• The cross-correlation search for a hot spot of gravitational waves
• All-sky, narrowband, gravitational-wave radiometry with folded data
• Stochastic gravitational wave background mapmaking using regularised deconvolution

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• Targeted search for the stochastic gravitational-wave background from the galactic millisecond pulsar population
• Angular Resolution of the Search for Anisotropic Stochastic Gravitational-Wave Background with Terrestrial Gravitational-Wave Detectors
• Jointly setting upper limits on multiple components of an anisotropic stochastic gravitational-wave background
• Model-independent search for anisotropies in stochastic gravitational-wave backgrounds and application to LIGO-Virgo's first three observing Runs