Supplement: Going the Distance: Mapping Host Galaxies of LIGO and Virgo Sources in Three Dimensions Using Local Cosmography and Targeted Follow-up

TL;DR

This paper presents a new 3D localization method for gravitational-wave sources, enabling efficient identification of potential host galaxies by combining sky maps with galaxy catalogs, aiding follow-up observations.

Contribution

It introduces a HEALPix-based file format and Python tools for manipulating 3D localizations, enhancing rapid volume reconstruction for gravitational-wave sources.

Findings

New HEALPix-based format for 3D localizations

Python tools for target galaxy ranking

Mathematical details of the volume reconstruction algorithm

Abstract

This is a supplement to the Letter of Singer et al. (https://arxiv.org/abs/1603.07333), in which we demonstrated a rapid algorithm for obtaining joint 3D estimates of sky location and luminosity distance from observations of binary neutron star mergers with Advanced LIGO and Virgo. We argued that combining the reconstructed volumes with positions and redshifts of possible host galaxies can provide large-aperture but small field of view instruments with a manageable list of targets to search for optical or infrared emission. In this Supplement, we document the new HEALPix-based file format for 3D localizations of gravitational-wave transients. We include Python sample code to show the reader how to perform simple manipulations of the 3D sky maps and extract ranked lists of likely host galaxies. Finally, we include mathematical details of the rapid volume reconstruction algorithm.