Catalog Matching with Astrometric Correction and its Application to the Hubble Legacy Archive

TL;DR

This paper introduces a new astrometric correction method and a Bayesian matching approach to improve object identification across overlapping astronomical images, demonstrated on the Hubble Legacy Archive.

Contribution

It presents a novel, efficient solution for relative astrometry and a Bayesian method for matching objects across multiple images, enhancing catalog accuracy.

Findings

Achieved sub-pixel positional accuracy of a few milli-arcseconds.

Developed a fast, analytic solution for astrometric corrections.

Created a high-quality, publicly available catalog of matched objects.

Abstract

Object cross-identification in multiple observations is often complicated by the uncertainties in their astrometric calibration. Due to the lack of standard reference objects, an image with a small field of view can have significantly larger errors in its absolute positioning than the relative precision of the detected sources within. We present a new general solution for the relative astrometry that quickly refines the World Coordinate System of overlapping fields. The efficiency is obtained through the use of infinitesimal 3-D rotations on the celestial sphere, which do not involve trigonometric functions. They also enable an analytic solution to an important step in making the astrometric corrections. In cases with many overlapping images, the correct identification of detections that match together across different images is difficult to determine. We describe a new greedy Bayesian approach for selecting the best object matches across a large number of overlapping images. The methods are developed and demonstrated on the Hubble Legacy Archive, one of the most challenging data sets today. We describe a novel catalog compiled from many Hubble Space Telescope observations, where the detections are combined into a searchable collection of matches that link the individual detections. The matches provide descriptions of astronomical objects involving multiple wavelengths and epochs. High relative positional accuracy of objects is achieved across the Hubble images, often sub-pixel precision in the order of just a few milli-arcseconds. The result is a reliable set of high-quality associations that are publicly available online.