HEALPix Alchemy: Fast All-Sky Geometry and Image Arithmetic in a Relational Database for Multimessenger Astronomy Brokers

Leo P. Singer, B. Parazin, Michael W. Coughlin, Joshua S. Bloom, Arien Crellin-Quick, Daniel A. Goldstein, Stéfan Van Der Walt

Research output: Contribution to journalArticlepeer-review


Efficient searches for electromagnetic counterparts to gravitational wave, high-energy neutrino, and gamma-ray burst events demand rapid processing of image arithmetic and geometry set operations in a database to cross-match galaxy catalogs, observation footprints, and all-sky images. Here we introduce HEALPix Alchemy, an open-source, pure Python implementation of a set of methods that enables rapid all-sky geometry calculations. HEALPix Alchemy is built upon HEALPix, a spatial indexing strategy that is widely used in astronomical databases as well as the native format of LIGO-Virgo-KAGRA gravitational-wave sky localization maps. Our approach leverages new multirange types built into the PostgreSQL 14 database engine. This enables fast all-sky queries against probabilistic multimessenger event localizations and telescope survey footprints. Questions such as "What are the galaxies contained within the 90% credible region of an event?"and "What is the rank-ordered list of the fields within an observing footprint with the highest probability of containing the event?"can be performed in less than a few seconds on commodity hardware using off-the-shelf cloud-managed database implementations without server-side database extensions. Common queries scale roughly linearly with the number of telescope pointings. As the number of fields grows into the hundreds or thousands, HEALPix Alchemy is orders of magnitude faster than other implementations. HEALPix Alchemy is now used as the spatial geometry engine within SkyPortal, which forms the basis of the Zwicky Transient Facility transient marshal, called Fritz.

Original languageEnglish (US)
Article number209
JournalAstronomical Journal
Issue number5
StatePublished - May 1 2022

Bibliographical note

Funding Information:
L.P.S. acknowledges support for this work from an Internal Scientist Funding Model (ISFM) award from NASA for the Time-domain Astrophysics Coordination Hub (TACH) work package, a Science Task Group award from the Science and Exploration Directorate at NASA Goddard Space Flight Center, and partial support from the Neil Gehrels Swift Observatory project. B.P. acknowledges support from a Northeastern Lawrence Co-op Fellowship. M.W.C. acknowledges support from the National Science Foundation with grant Nos. PHY-2010970 and OAC-2117997. J.S.B. was partially supported by a Gordon and Betty Moore Foundation Data-Driven Discovery grant. The authors thank Israel Martinez-Castellanos and Paul Jungwirth for feedback and suggestions on this paper.

Funding Information:
Based on observations obtained with the Samuel Oschin 48 inch Telescope and the 60 inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.

Publisher Copyright:
© 2022. The Author(s). Published by the American Astronomical Society.


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