Limits of Astrophysics with Gravitational-Wave Backgrounds

TL;DR

This paper discusses the limitations of current gravitational-wave detectors in extracting astrophysical information from the binary black hole background and how it acts as a foreground that hampers detecting other cosmological signals.

Contribution

It analyzes the challenges in extracting astrophysical parameters from the binary black hole background and quantifies its impact as a foreground noise.

Findings

Current detectors struggle to extract detailed astrophysical information.

The binary black hole background limits the detection of other stochastic signals.

Quantitative assessment of foreground effects on future observations.

Abstract

The recent Advanced LIGO detection of gravitational waves from the binary black hole GW150914 suggests there exists a large population of merging binary black holes in the Universe. Although most are too distant to be individually resolved by advanced detectors, the superposition of gravitational waves from many unresolvable binaries is expected to create an astrophysical stochastic background. Recent results from the LIGO and Virgo collaborations show that this astrophysical background is within reach of Advanced LIGO. In principle, the binary black hole background encodes interesting astrophysical properties, such as the mass distribution and redshift distribution of distant binaries. However, we show that this information will be difficult to extract with the current configuration of advanced detectors (and using current data analysis tools). Additionally, the binary black hole background also constitutes a foreground that limits the ability of advanced detectors to observe other interesting stochastic background signals, for example from cosmic strings or phase transitions in the early Universe. We quantify this effect.