Gravitational-wave inference in the catalog era: evolving priors and marginal events

TL;DR

This paper develops a formalism to incorporate marginal gravitational-wave events with uncertain origins into population studies, improving the accuracy of astrophysical inferences as detection catalogs grow.

Contribution

It introduces a new method to account for ambiguous event origins in gravitational-wave population analyses, utilizing $p_ ext{astro}$ estimates to refine results.

Findings

Derived a formalism for population studies with ambiguous events

Applied the method to GWTC-1 and IAS catalog data

Showed how population parameter estimates change with $p_ ext{astro}$

Abstract

As the number of gravitational-wave transient detections grows, the inclusion of marginally significant events in gravitational-wave catalogs will lead to increasing contamination from false positives. In this paper, we address the question of how to carry out population studies in light of the fact that some fraction of marginally significant gravitational-wave events are of terrestrial origin. We show that previously published estimates of $p_\text{astro}$, the probability that an event is of astrophysical origin, imply an effective noise likelihood, which can be used to take into account the uncertain origin of marginal events in population studies. We derive a formalism to carry out population studies with ambiguous gravitational-wave events. We demonstrate this formalism using events from the LIGO/Virgo Gravitational-Wave Transient Catalog 1 (GWTC-1) as well as events from the Venumadhav et al. "IAS catalog." We derive posterior distributions for population parameters and discuss how they change when we take into account $p_\text{astro}$. We provide updated individual-event posterior distributions by including population information.