Mapping incoherent gravitational wave backgrounds

Abstract

Given the recent detection of gravitational waves from individual sources it is almost a certainty that some form of background of gravitational waves will be detected in future. The most promising candidate for such a detection are backgrounds made up of incoherent superposition of the signal of unresolved astrophysical or, backgrounds sourced by earlier cosmological events. Such backgrounds will also contain anisotropies about an average value. The information contained in the background level and any anisotropies will be extremely valuable as an astrophysical and cosmological probe. As such, the ability to reconstruct sky maps of the signal will become important as the sensitivity increases. We build and test a pixel-based, maximum-likelihood Gravitational Wave Background (GWB) map-maker that uses the cross-correlation of sets of generalised baselines as input. The resulting maps are a representation of the GWB power, or strain "intensity" on the sky. We test the algorithm by reconstructing known input maps with different baseline configurations. We also apply the map-maker to a subset of the Advance LIGO data.

Improved limits on a stochastic gravitational-wave background and its anisotropies from Advanced LIGO O1 and O2 runs

“…In this paper we implement the mapping procedure described in detail in [13], previously applied to Advanced LIGO open data set O1 in [14], to the second Advanced LIGO data set, O2, which spans from 30 November, 2016 to August, 2017. The algorithm extracts the maximumlikelihood estimate for the SGWB integrating over filtered time-stream data cross-correlated between a pair of detectors.…”

“…The maximum-likelihood map of the SGWB intensity is then constructed following [13]. The algorithm accumulates a noise-weighted projection of the time-stream data into map z p and weight matrix M pp over time,…”

“…The noise fitting procedure masks a number of these regions in order to reduce the bias in the parametrised model. framework for a network of more than two detectors, as described in [13]. The independence and complementarity of this approach with respect to the LIGO one will be very useful as we approach the sensitivity levels required for a detection.…”

Estimating the angular power spectrum of the gravitational-wave background in the presence of shot noise

“…Since the components of CBCs are the results of stellar evolution, they should reside in galaxies, 1 and the AGWB should trace the distribution of galaxies throughout the local Universe. There has therefore been significant recent interest in AGWB anisotropies [15][16][17][18][19][20][21] and associated observational searches [22][23][24] and data-analysis methods [25][26][27][28][29][30][31], as these might provide an entirely new probe of galaxy clustering and large-scale structure (LSS).…”

Life of cosmological perturbations in modified dispersion relation models and the prospect of traveling primordial gravitational waves

“…Once again, inflation falls victim of its pliability. The issue of detectability with reference to the standing/stationary nature of the waves has been examined in [27,28].…”