Distances of Terzan 5, Liller 1, UKS 1, and Terzan 4 based on HST NICMOS photometry

Terzan 5, Liller1, UKS1, Terzan 4 :: new paper

Distances of the bulge globular clusters Terzan 5, Liller 1, UKS 1, and Terzan 4 based on HST NICMOS photometry

Authors: S. Ortolani, B. Barbuy, E. Bica, M. Zoccali, and A. Renzini

Abstract: A large number of pulsars and X-rays sources are detected in globular clusters. To understand the structure and content of these clusters, accurate distances are required. We derive the distances of Terzan 5, Liller 1 and UKS 1 using as a reference a recent distance determination of NGC 6528, based on HST/NICMOS and NTT/SOFI infrared photometry. The distance of the metal-poor cluster Terzan 4 was derived from a comparison with M 92 in NICMOS bands.Methods.Distances of the metal-rich clusters are obtained by comparison of the Horizontal Branch (HB) level of the clusters, relative to the reddening line passing through the HB of NGC 6528. We use methods based on NICMOS bands and transformations to J and H magnitudes with different assumptions. Liller 1 and Terzan 4 are found to be at the central bulge distance, UKS 1 is beyond the Galactic center, while Terzan 5 is closer to the Sun than the other four clusters (…)

Astronomy & Astrophysics 470, 1043-1049 (2007)
Abstract :: Free PDF of the whole paper (248.9 KB)


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