Jointly setting upper limits on multiple components of an anisotropic stochastic gravitational-wave background

Abstract

With the increasing sensitivities of the gravitational wave (GW) detectors and more detectors joining the international network, the chances of detection of a stochastic GW background (SGWB) are progressively increasing. Different astrophysical and cosmological processes are likely to give rise to backgrounds with distinct spectral signatures and distributions on the sky. The observed SGWB will therefore be a superposition of these components. Hence, one of the first questions that will come up after the first detection of a SGWB will likely be about identifying the dominant components and their distributions on the sky. Both these questions were addressed separately in the literature, namely, how to separate components of isotropic backgrounds and how to probe the anisotropy of a single component. Here, we address the question of how to separate distinct anisotropic backgrounds with (sufficiently) different spectral shapes. We first obtain the combined Fisher information matrix from folded data using an efficient analysis pipeline PyStoch, which incorporates covariances between pixels and spectral indices. This is necessary for estimating the detection statistic and setting upper limits. However, based on a recent study, we ignore the pixel-to-pixel noise covariance that does not have a significant effect on the results at the present sensitivity levels of the detectors. We show that the joint analysis accurately separates and estimates backgrounds with different spectral shapes and different sky distributions with no major bias. This does come at the cost of increased variance. Thus making the joint upper limits safer, though less strict than the individual analysis. We finally set joint upper limits on the multicomponent anisotropic background using Advanced LIGO data taken up to the first half of the third observing run.

14 pages, 10 figures, 2 tables

References in corpus (18)

• Advanced Virgo: a 2nd generation interferometric gravitational wave detector
• The stochastic gravitational-wave background from massive black hole binary systems: implications for observations with Pulsar Timing Arrays
• CMasher: Scientific colormaps for making accessible, informative and 'cmashing' plots
• Directional limits on persistent gravitational waves from Advanced LIGO's first observing run
• The Science Case for LIGO-India
• Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo's first three observing runs
• Gravitational wave radiometry: Mapping a stochastic gravitational wave background
• Measuring the primordial gravitational-wave background in the presence of astrophysical foregrounds
• StarTrack predictions of the stochastic gravitational-wave background from compact binary mergers
• Simultaneous estimation of astrophysical and cosmological stochastic gravitational-wave backgrounds with terrestrial detectors
• Gravitational wave background from rotating neutron stars
• Measuring neutron-star ellipticity with measurements of the stochastic gravitational-wave background
• Detecting a Stochastic Gravitational-Wave Background: The Overlap Reduction Function
• A synthetic model of the gravitational wave background from evolving binary compact objects
• Detection regimes of the cosmological gravitational wave background from astrophysical sources
• Unified mapmaking for an anisotropic stochastic gravitational wave background
• Upper limits on persistent gravitational waves using folded data and the full covariance matrix from Advanced LIGO${}^{\prime }$s first two observing runs
• Component separation map-making for stochastic gravitational wave background

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