All of the Sky: HEALPix Density Maps of Gaia-scale Datasets from the Database to the Desktop

TL;DR

This paper explores methods for creating and visualizing all-sky HEALPix density maps from Gaia-scale datasets using TAP services, discussing technical requirements and new visualization capabilities.

Contribution

It introduces practical approaches and requirements for generating and visualizing HEALPix density maps from large astronomical datasets via TAP services.

Findings

Feasibility of producing all-sky HEALPix maps from Gaia data

Requirements for TAP/RDBMS services to support such queries

New visualization features in TOPCAT

Abstract

The Gaia Archive provides access to observations of around a billion sky sources. The primary access to this archive is via TAP services such as GACS and ARI-Gaia, which allow execution of SQL-like queries against a large remote database returning a result set of manageable size for client-side use. Such services are generally used for extracting relatively small source lists according to potentially complex selection criteria. But they can also be used to obtain statistical information about all, or a large fraction of, the observed sources by building histogram-like results. We examine here the practicalities of producing and consuming all-sky HEALPix weighted density maps in this way for Gaia and other large datasets. We present some modest requirements on TAP/RDBMS services to enable such queries, and discuss visualisation and serialization options for the results including some new capabilities in recent versions of TOPCAT.