HST NICMOS photometry of the reddened bulge globular clusters NGC 6528, Terzan 5, Liller 1, UKS 1 and Terzan 4

• Autor(a) principal: Ortolani, Sergio
• Data de Publicação: 2001
• Outros Autores: Barbuy, Beatriz, Bica, Eduardo Luiz Damiani, Renzini, Alvio, Zoccali, Manuela, Rich, Robert Michael, Cassisi, Santi
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFRGS
• Texto Completo: http://hdl.handle.net/10183/98502
• topic: Galaxia; Aglomerados estelares globulares; Evolucao estelar; Fotometria estelar; Galaxy: globular clusters: individual: NGC 6528, Terzan 5, Liller 1, Terzan 4 UKS 1; Stars: CM diagram

We present results from NICMOS Hubble Space Telescope observations of the reddened bulge globular clusters NGC 6528, Terzan 5, Liller 1, UKS 1 and Terzan 4, obtained through the filters F110W (1.1 μm) and F160W (1.6 μm) (nearly equivalent to J and H). For the first time the turnoff region of Liller 1 and the main sequence of Terzan 5 and Terzan 4 are reached, as well as the horizontal branch of UKS 1. The magnitude difference between the turno and the red horizontal branch Δm₁₁₀ = mHB₁₁₀ − mTO₁₁₀ is used as an age indicator. From comparisons with new isochrones in the NICMOS photometric system, we conclude that the two metal-rich clusters NGC 6528 and Terzan 5 are coeval within uncertainties (~20%) with 47 Tucanae. Liller 1 and UKS 1 are confirmed as metal-rich globular clusters. Terzan 4 is confirmed as an interesting case of a metal-poor cluster in the bulge with a blue horizontal branch.