ON THE RADIAL DISTRIBUTION OF HORIZONTAL BRANCH STARS IN NGC 2808

Iannicola G.; Monelli, M; Bono, G; Stetson, PB; Buonanno R.; Calamida, A; Zoccali, M; Caputo F.; Castellani, M.; Corsi, CE; Dall’Ora M.; Di Cecco A.; Degl'Innocenti S.; Ferraro I.; Nonino, M; et. al.

Abstract

We present accurate new ultraviolet and optical BVI photometry for the Galactic globular cluster NGC 2808 based on both ground-based and archival Hubble Space telescope imagery. From this we have selected a sample of 2000 Horizontal Branch (HB) stars; given the extensive wavelength range considered and the combination of both high angular resolution and wide-field photometric coverage, our sample should be minimally biased. We divide the HB stars into three radial bins and find that the relative fractions of cool, hot, and extreme HB stars do not change radically when moving from the center to the outskirts of the cluster: the difference is typically smaller than 2s. These results argue against the presence of strong radial differentiation among any stellar subpopulations having distinctly different helium abundances. The ratio between HB and red giant (RG) stars brighter than the ZAHB steadily increases when moving from the innermost to the outermost cluster regions. The difference is larger than 4s and indicates a deficiency of bright RGs in the outskirts of the cluster. © 2009. The American Astronomical Society. All rights reserved.

Más información

Título según WOS: ON THE RADIAL DISTRIBUTION OF HORIZONTAL BRANCH STARS IN NGC 2808
Título según SCOPUS: On the radial distribution of horizontal branch stars in NGC 2808
Título de la Revista: ASTROPHYSICAL JOURNAL LETTERS
Volumen: 696
Número: 2
Editorial: IOP PUBLISHING LTD
Fecha de publicación: 2009
Página de inicio: L120
Página final: L124
Idioma: English
URL: http://stacks.iop.org/1538-4357/696/i=2/a=L120?key=crossref.c43b36cb72fb79ffa5063233045a67c2
DOI:

10.1088/0004-637X/696/2/L120

Notas: ISI, SCOPUS