High-precision astrometry and photometry with the JWST/MIRI imager

TL;DR

This paper develops and tests high-precision astrometry and photometry techniques for JWST's MIRI imager, adapting lessons from HST to enhance data analysis and enable future astronomical observations.

Contribution

It introduces detailed methods for creating effective PSF models and geometric distortion corrections for JWST/MIRI, with publicly available tools for the community.

Findings

High-precision astrometry achievable with MIRI data

Effective PSF models improve photometric accuracy

Geometric distortion corrections are stable over time

Abstract

Astrometry is one of the main pillars of astronomy, and one of its oldest branches. Over the years, an increasing number of astrometric works by means of Hubble Space Telescope (HST) data have revolutionized our understanding of various phenomena. With the launch of JWST, it becomes almost instinctive to want to replicate or improve these results with data taken with the newest, state-of-the-art, space-based telescope. In this regard, the initial focus of the community has been on the Near-Infrared (NIR) detectors on board of JWST because of their high spatial resolution. This paper begins the effort to capture and apply what has been learned from HST to the Mid-InfraRed Instrument (MIRI) of JWST by developing the tools to obtain high-precision astrometry and photometry with its imager. We describe in detail how to create accurate effective point-spread-function (ePSF) models and geometric-distortion corrections, analyze their temporal stability, and test their quality to the extent of what is currently possible with the available data in the JWST MAST archive. We show that careful data reduction provides deep insight on the performance and intricacies of the MIRI imager, and of JWST in general. In an effort to help the community to devise new observing programs, we make our ePSF models and geometric-distortion corrections publicly available.