Odyssey: A Public GPU-Based Code for General-Relativistic Radiative Transfer in Kerr Spacetime

TL;DR

Odyssey is a GPU-accelerated, publicly available code for efficient and accurate general-relativistic radiative transfer calculations in Kerr spacetime, aiding black hole imaging and spectroscopy.

Contribution

We introduce Odyssey, a fast, flexible GPU-based code for ray tracing and radiative transfer in Kerr spacetime, including an educational tool for visualizing geodesics.

Findings

Performance exceeds 1 nanosecond per photon per integration step on a single GPU

Odyssey is publicly available, fast, and adaptable for various research needs

Includes Odyssey_Edu, a real-time visualization tool for Kerr geodesics

Abstract

General-relativistic radiative transfer (GRRT) calculations coupled with the calculation of geodesics in the Kerr spacetime are an essential tool for determining the images, spectra and light curves from matter in the vicinity of black holes. Such studies are especially important for ongoing and upcoming millimeter/submillimeter (mm/sub-mm) Very Long Baseline Interferometry (VLBI) observations of the supermassive black holes at the centres of Sgr A^{*} and M87. To this end we introduce Odyssey, a Graphics Processing Unit(GPU)-based code for ray tracing and radiative transfer in the Kerr spacetime. On a single GPU, the performance of Odyssey can exceed 1 nanosecond per photon, per Runge-Kutta integration step. Odyssey is publicly available, fast, accurate, and flexible enough to be modified to suit the specific needs of new users. Along with a Graphical User Interface (GUI) powered by a video-accelerated display architecture, we also present an educational software tool, Odyssey_Edu, for showing in real time how null geodesics around a Kerr black hole vary as a function of black hole spin and angle of incidence onto the black hole.