Projection effects on the observed angular spectrum of the astrophysical
  stochastic gravitational wave background
  The detection and characterization of the Stochastic Gravitational Wave
Background (SGWB) is one of the main goals of Gravitational Wave (GW)
experiments. The observed SGWB will be the combination of GWs from cosmological
(as predicted by many models describing the physics of the early Universe) and
astrophysical origins, which will arise from the superposition of GWs from
unresolved sources whose signal is too faint to be detected. Therefore, it is
important to have a proper modeling of the astrophysical SGWB (ASGWB) in order
to disentangle the two signals; moreover, this will provide additional
information on astrophysical properties of compact objects. Applying the Cosmic
Rulers formalism, we compute the observed ASGWB angular power spectrum, hence
using gauge invariant quantities, accounting for all effects intervening
between the source and the observer. These are the so-called projection
effects, which include Kaiser, Doppler and gravitational potentials effect. Our
results show that these projection effects are the most important at the
largest scales, and they contribute to up to tens of percent of the angular
power spectrum amplitude, with the Kaiser term being the largest at all scales.
While the exact impact of these results will depend on instrumental and
astrophysical details, a precise theoretical modeling of the ASGWB will
necessarily need to include all these projection effects.
