Gravitational-Wave Background Sky Maps from Advanced LIGO O1 Data

Area of Science:

• Astrophysics
• Cosmology
• Gravitational Wave Astronomy

Background:

• The search for a persistent gravitational-wave background (GWB) is crucial for understanding cosmic sources.
• Previous studies have focused on specific signal models, limiting comprehensive analysis.

Purpose of the Study:

• To integrate publicly available O1 LIGO data for maximum-likelihood constraints on the GWB.
• To produce sky maps of strain intensity and derive upper limits on GWB density and anisotropy.

Main Methods:

• Utilized publicly available O1 LIGO time-domain data.
• Developed a method to generate sky maps of strain intensity (I) at a reference frequency (f₀).
• Assumed fixed power-law spectra for signal integration to derive upper limits on ΩGW(f₀) and anisotropy.

Main Results:

• Established 95% confidence upper limits of ΩGW < 4.8×10⁻⁷ at f₀ = 50 Hz.
• Provided similar constraints on dipole modulation for inspiral-dominated stochastic background scenarios.
• Generated sky maps detailing GWB intensity across the celestial sphere.

Conclusions:

• The study provides significant upper limits on the persistent gravitational-wave background.
• The methodology allows for mapping GWB intensity and anisotropy, advancing detection capabilities.
• Results contribute to constraining astrophysical and cosmological models of gravitational wave generation.