Proper Motions in Globular Clusters using Deconvolution of HST Images

TL;DR

This paper extends a deconvolution technique for HST images to measure stellar proper motions in globular clusters, aiming to detect intermediate-mass black holes through dynamical analysis.

Contribution

It adapts and benchmarks a sub-sampled deconvolution method for precise proper motion measurements in crowded globular cluster fields.

Findings

Demonstrated improved astrometric accuracy with the method

Validated the technique using real and simulated HST data

Enabled potential detection of intermediate-mass black holes

Abstract

A sub-sampled deconvolution technique for crowded field photometry with the HST WFPC2 instrument was proposed by Butler (2000) and applied to search for optical counterparts to pulsars in globular clusters (Golden et al. 2001). Simulations showed that the method, which takes account of the point-spread function (PSF) spatial variation, can provide better star detection and recovers the resolution lost to aberrations and poor sampling. The original emphasis was on precision photometry in crowded fields. In the present work, we have extended this technique to determine proper motions of stars in globular clusters. Actual HST images of the globular clusters, along with realistic simulations of the globular clusters, were used to benchmark the technique for astrometric accuracy. The ultimate aim is to use this dynamical data to search for intermediate-mass black holes in globular cluster cores.