The unresolved stochastic background from compact binary mergers detectable by next-generation ground-based gravitational-wave observatories

• Main Authors: Bellie, Darsan S, Banagiri, Sharan, Doctor, Zoheyr, Kalogera, Vicky
• Format: Journal Article
• Language: English
• Published: 03-10-2023
• Subjects: Physics - General Relativity and Quantum Cosmology; Physics - High Energy Astrophysical Phenomena; Physics - High Energy Physics - Phenomenology
• DOI: 10.48550/arxiv.2310.02517

The next generation of ground-based gravitational-wave detectors will look
much deeper into the Universe and have unprecedented sensitivities and
low-frequency capabilities. Especially alluring is the possibility of detecting
an early-Universe cosmological stochastic background that could provide
important insights into the beginnings of our Universe and fundamental physics
at extremely high energies. However, even if next-generation detectors are
sensitive to cosmological stochastic backgrounds, they will be masked by more
dominant astrophysical backgrounds, namely the residual background from the
imperfect subtraction of resolvable compact binary coalescences (CBCs) as well
as the CBC background from individually unresolvable CBCs. Using our latest
knowledge of masses, rates, and delay time distributions, we present a
data-driven estimate of the unresolvable CBC background that will be seen by
next-generation detectors. Accounting for statistical and systematic errors,
this estimate quantifies an important piece in the CBC noise budget for
next-generation detectors and can help inform detector design and subtraction
algorithms. We compare our results with predictions for backgrounds from
several cosmological sources in the literature, finding that the unresolvable
background will likely be a significant impediment for many models. This
motivates the need for simultaneous inference methods or other statistical
techniques to detect early-Universe cosmological backgrounds.