The ligo.skymap package provides tools for reading, writing, generating, and visualizing gravitational-wave probability maps from LIGO and Virgo. Some of the key features of this package are:

  • Command line tool bayestar-localize-coincs: BAYESTAR, providing rapid, coherent, Bayesian, 3D position reconstruction for compact binary coalescence events

  • Command line tool ligo-skymap-from-samples: Create 3D sky maps from posterior sample chains using kernel density estimation

  • Command line tool ligo-skymap-plot: An everyday tool for plotting HEALPix maps

  • Module ligo.skymap.plot.allsky: Astronomical mapmaking tools for perfectionists and figure connoisseurs

GW170817 localization

This illustration of the position of GW170817, prepared using ligo.skymap, illustrates the main features of this package: rapid localization of compact binaries with BAYESTAR 1, three-dimensional density estimation 2 3, cross-matching with galaxy catalogs, and visualization of gravitational-wave sky maps. Reproduced from 4.

Quick Start, Tutorials


Coordinate Frames (ligo.skymap.coordinates)

I/O and Data Format Support (

Plotting and Visualization (ligo.skymap.plot)

Sky Map Postprocessing (ligo.skymap.postprocess)



Command Line Tools

BAYESTAR Rapid Sky Localization

Sky Map Visualization


Developer Info




Singer, L. P., & Price, L. R. 2016, Phys. Rev. D, 93, 024013. doi:10.1103/PhysRevD.93.024013


Singer, L. P., Chen, H.-Y., Holz, D. E., et al. 2016, Astropys. J. Lett., 829, L15. doi:10.3847/2041-8205/829/1/L15


Singer, L. P., Chen, H.-Y., Holz, D. E., et al. 2016, Astropys. J. Supp., 226, 10. doi:10.3847/0067-0049/226/1/10


Kasliwal, M. M., Nakar, E., Singer, L. P. et al. 2019, Science, 358, 1559. doi:10.1126/science.aap9455