The origin of an extended X-ray emission apparently associated with the globular cluster 47 Tucanae

Abstract

Using the Suzaku X-ray Imaging Spectrometer, we performed a 130 ks observation of an extended X-ray emission, which was shown by ROSAT and Chandra observations to apparently associate with the globular cluster 47 Tucanae. The obtained $0.5-6$ keV spectrum was successfully fitted with a redshifted thin thermal plasma emission model whose temperature and redshift are $2.2^{+0.2}_{-0.3} $keV (at the rest frame) and $0.34\pm0.02$, respectively. Derived parameters, including the temperature, redshift, and luminosity, indicate that the extended X-ray source is a background cluster of galaxies, and its projected location falls, by chance, on the direction of the proper motion of 47 Tucanae.