Toward High‐Precision Astrometry with WFPC2. I. Deriving an Accurate Point‐Spread Function

By Jay Anderson, Ivan R. King. 2000

322 citations recorded by the source corpus.

The first step toward doing high‐precision astrometry is the measurement of individual stars in individual images, a step that is fraught with dangers when the images are undersampled. The key to avoiding systematic positional error in undersampled images is to determine an extremely accurate point‐spread function (PSF). We apply the concept of the effective PSF (ePSF) and show that in images that consist of pixels it is the ePSF, rather than the often‐used instrumental PSF, that embodies the information from which accurate star positions and magnitudes can be derived. We show how, in a rich star field, one can use the information from dithered exposures to derive an extremely accurate effective PSF by iterating between the PSF itself and the star positions that we measure with it. We also give a simple but effective procedure for representing spatial variations of the Hubble Space Telescope PSF. With such attention to the PSF, we find that we are able to measure the position of a single reasonably bright star in a single image with a precision of 0.02 pixel (2 mas in WF frames, 1 mas in PC), but with a systematic accuracy better than 0.002 pixel (0.2 mas in WF, 0.1 mas in PC), so that multiple observations can reliably be combined to improve the accuracy by √N.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/d8ea5a0561e4a2f894ccff46de42508f40600050

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Jay Anderson
2. G. Piotto
3. A. Milone
4. L. Bedin
5. Aaron Dotter
6. A. Renzini
7. A. Sarajedini
8. A. Marino

In Atomic and Molecular Physics, and Optics

1. Jay Anderson
2. L. Bedin
3. G. Piotto
4. R. P. van der Marel
5. N. Smith
6. M. M. Kiminki
7. M. Reiter
8. Santi Cassisi

Citations in the corpus

• The ACS survey of Galactic globular clusters. XII. Photometric binaries along the main sequence (2011, methodology): “The WFPC2 data are analyzed by using the programs and the techniques described in Anderson & King (1999, 2000, 2003).”
• An Improved Distortion Solution for the Hubble Space Telescope’s WFPC2 (2002, background): “Since with proper attention to the point-spread function (PSF) the position of a single star image can be measured with an accuracy of 0.02 pixel (Anderson & King 2000, hereafter AK00), and we wish to reduce this error even more by averaging positions from a number of images, it is clear that…”
• Simulation of a Space-based Microlensing Survey for Terrestrial Extrasolar Planets (2000, background): “Anderson and King (2000) argue that centroids can be measured to 0.2% of a pixel with a combination of a set of undersampled HST WFPC2 frames that have been dithered to recover the resolution lost to undersampling.”
• Stellar Proper Motions in the Galactic Bulge from Deep Hubble Space Telescope ACS WFC Photometry (2008, background): “This approach rests on the existence of a highly supersampled model for the ‘‘effective PSF’’ (the instrumental PSF as recorded by the detector, hereafter ePSF; for discussion see Anderson & King 2000).”
• ω Centauri: The Population Puzzle Goes Deeper (2004, methodology): “All these images have been2 # 400 reduced with the algorithms described in Anderson & King (2000).”
• Hubble Space Telescope Evidence for an Intermediate-Mass Black Hole in the Globular Cluster M15. II. Kinematic Analysis and Dynamical Modeling (2002, background): “It has been demonstrated that such studies are feasible with HST (e.g., Anderson & King 2000).”
• Ancient eruptions of η Carinae: a tale written in proper motions (2016, methodology): “The measured positions were then corrected for the 34throw anomaly (Anderson & King 1999) and for geometric distortion (Anderson & King 2000).”
• Transforming observational data and theoretical isochrones into the ACS/WFC Vega-mag system (2004, methodology): “We obtained the ePSF from a set of images from a different project using the same filters, because the dithering of GO-9453 images was unsuitable to constrain the ePSF shape (Anderson & King 2000).”