The Spectral Energy Distributions of White Dwarfs in 47 Tucanae: The Distance to the Cluster

TL;DR

This study determines the distance to globular cluster 47 Tucanae by fitting white dwarf spectral energy distributions using Hubble Space Telescope data, providing a precise distance measurement and searching for infrared excesses.

Contribution

It introduces a new distance measurement method for 47 Tucanae based on white dwarf SED fitting with high-precision HST photometry.

Findings

Distance modulus (m - M)o=13.36 with small uncertainties

Distance to 47 Tucanae is approximately 4.70 kpc

No infrared excesses found in white dwarf sample

Abstract

We present a new distance determination to the Galactic globular cluster 47 Tucanae by fitting the spectral energy distributions of its white dwarfs to pure hydrogen atmosphere white dwarf models. Our photometric dataset is obtained from a 121 orbit Hubble Space Telescope program using the Wide Field Camera 3 UVIS/IR channels, capturing F390W, F606W, F110W, and F160W images. These images cover more than 60 square arcmins and extend over a radial range of 5-13.7 arcmin (6.5-17.9 pc) within the globular cluster. Using a likelihood analysis, we obtain a best fitting unreddened distance modulus of (m - M)o=13.36+/-0.02+/-0.06 corresponding to a distance of 4.70+/-0.04+/-0.13 kpc, where the first error is random and the second is systematic. We also search the white dwarf photometry for infrared excess in the F160W filter, indicative of debris disks or low mass companions, and find no convincing cases within our sample.