On the radial distribution of horizontal branch stars in ngc2808
arXiv:0903.4531 · doi:10.1088/0004-637X/696/2/L120
Abstract
We present accurate new ultraviolet and optical BVI photometry for the Galactic globular cluster ngc2808, based on both ground-based and archival HST imagery. From this we have selected a sample of ~2,000 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 ~2sigma. These results argue against the presence of strong radial differentiation among any stellar subpopulations having distinctly different helium abundances. The ratio between HB and RG stars brighter than the ZAHB steadly increases when moving from the innermost to the outermost cluster regions. The difference is larger than ~4sigma and indicates a deficiency of bright RGs in the outskirts of the cluster.
accepted for publication on ApJ Letters
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Cited by in corpus (7)
- The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. X. The radial distribution of stellar populations in NGC 2808
- Chemical Complexity in the Eu-enhanced Monometallic Globular Cluster NGC 5986
- A possible formation channel for blue hook stars in globular cluster
- Horizontal branch morphology: A new photometric parametrization
- Investigation of the Globular Cluster NGC 2808 with the Ultra-Violet Imaging Telescope
- Stellar-Encounter Driven Red-Giant Star Mass-Loss in Globular Clusters
- A Wide View of the Galactic Globular Cluster NGC 2808: Red Giant and Horizontal Branch Star Spatial Distributions