Enhancing gravitational-wave host localization with SKYFAST: rapid volume and inclination angle reconstruction

TL;DR

SKYFAST is a rapid localization pipeline for gravitational-wave events that reconstructs source parameters efficiently, enabling faster electromagnetic follow-up and host galaxy identification, crucial for multi-messenger astronomy.

Contribution

The paper introduces SKYFAST, a novel Bayesian non-parametric method that accelerates gravitational-wave source localization using posterior samples, reducing analysis time significantly.

Findings

Provides accurate sky position, distance, and inclination angle with fewer samples.

Generates ranked galaxy host list within minutes for follow-up.

Enhances electromagnetic counterpart identification efficiency.

Abstract

The scientific impact of GW170817 strongly supports the need for an efficient electromagnetic follow-up campaign to gravitational-wave event candidates. The success of such campaigns depends critically on a fast and accurate localization of the source. In this paper, we present SKYFAST, a new pipeline for rapid localization of gravitational-wave event hosts. SKYFAST runs alongside a full parameter estimation (PE) algorithm, from which posterior samples are taken. It uses these samples to reconstruct an analytical posterior for the sky position, luminosity distance, and inclination angle using a Dirichlet Process Gaussian Mixture Model, a Bayesian non-parametric method. This approach allows us to provide an accurate localization of the event using only a fraction of the total samples produced by the full PE analysis. Depending on the PE algorithm employed, this can lead to significant time savings, which is crucial for identifying the electromagnetic counterpart. Additionally, in a few minutes, SKYFAST generates a ranked list of the most probable galaxy hosts from a galaxy catalog of choice. This list includes information on the inclination angle posterior conditioned to the position of each candidate host, which is useful for assessing the detectability of gamma-ray burst structured jet emissions.