Working with Gravitational-Wave sky localizations: new methods and implementations

The era of multi-messenger astrophysics with Gravitational Waves (GW) requires the exploration and development of suitable methods and tools for real-time analysis as well as post-processing activities. The irregular and complex shapes of the GW sky localizations represent a new challenge for observational astronomers, who need to work with fast tiling, catalog queries, transient localizations, visibility and sky map comparisons. Here we show how gravitational-wave sky maps can be easily and efficiently visualized and processed using Multi-Order Coverage (MOC) maps. These maps are based on HEALPix sky tessellation which uses both Python language and the recent implementation in Aladin Desktop/Lite. In addition to this, we describe a specific interactive script, named GWsky, that we developed to effectively tile the sky localization of a gravitational-wave event providing accurate telescope pointings. We also show applications of these methods and tools for educational purposes in Virtual Reality Apps, high resolution images, and basic sonification of the GW sky maps. Finally, we describe possible evolutions of such implementations when three or more ground-based interferometers will be involved in a gravitational-wave source localization (i.e. Virgo,LIGO–Hanford, LIGO–Livingston, KAGRA, LIGO–India) with a corresponding increase of the sky map resolution.