Kavli Affiliate: Lijing Shao
| First 5 Authors: Hanlin Song, Dicong Liang, Ziming Wang, Lijing Shao,
| Summary:
Stochastic gravitational-wave (GW) background (SGWB) contains information
about the early Universe and astrophysical processes. The recent evidence of
SGWB by pulsar timing arrays in the nanohertz band is a breakthrough in the GW
astronomy. For ground-based GW detectors, while in data analysis, the SGWB can
be masked by loud GW events from compact binary coalescences (CBCs). Assuming a
next-generation ground-based GW detector network, we investigate the potential
for detecting the astrophysical and cosmological SGWB with non-CBC origins by
subtracting recovered foreground signals of loud CBC events. The Fisher
Information Matrix (FIM) method is adopted for quick calculation. As an
extension of the studies by Sachdev {it et al.} (2020) and Zhou {it et al.}
(2023), two more essential features are considered. Firstly, we incorporate
non-zero aligned or anti-aligned spin parameters in our waveform model. Because
of the inclusion of spins, we obtain significantly more pessimistic results
than the previous work, where the residual energy density of foreground is even
larger than the original CBC foreground. For the most extreme case, we observe
that the subtraction results are approximately 10 times worse for binary black
hole events and 20 times worse for binary neutron star events than the
scenarios without accounting for spins. The degeneracy between the spin
parameters and the symmetric mass ratio is strong in the parameter estimation
process, and it contributes most to the imperfect foreground subtraction.
Secondly, in this work, extreme CBC events with condition numbers of FIMs
$c_{rm{Gamma}}>10^{15}$ are preserved. The impacts of these extreme events on
foreground subtraction are discussed. Our results have important implications
for assessing the detectability of SGWB from non-CBC origins for ground-based
GW detectors.
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