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The gradients in the 47 Tuc red giant branch bump and horizontal branch are consistent with a centrally concentrated, helium-enriched second stellar generation

Nataf, David; Gould, A; Pinsonneault, Marc H; Stetson, Peter B

Description

We combine ground- and space-based photometry of the Galactic globular cluster 47 Tuc to measure four independent lines of evidence for a helium gradient in the cluster, whereby stars in the cluster outskirts would have a lower initial helium abundance than stars in and near the cluster core. For our first and second lines of evidence, we show that the red giant branch bump stars exhibit gradients in their number counts and brightness. With increased separation from the cluster center, they...[Show more]

dc.contributor.authorNataf, David
dc.contributor.authorGould, A
dc.contributor.authorPinsonneault, Marc H
dc.contributor.authorStetson, Peter B
dc.date.accessioned2015-12-10T23:22:56Z
dc.identifier.issn0004-637X
dc.identifier.urihttp://hdl.handle.net/1885/66729
dc.description.abstractWe combine ground- and space-based photometry of the Galactic globular cluster 47 Tuc to measure four independent lines of evidence for a helium gradient in the cluster, whereby stars in the cluster outskirts would have a lower initial helium abundance than stars in and near the cluster core. For our first and second lines of evidence, we show that the red giant branch bump stars exhibit gradients in their number counts and brightness. With increased separation from the cluster center, they become more numerous relative to the other red giant stars. They also become fainter. For our third and fourth lines of evidence, we show that the horizontal branch of the cluster becomes both fainter and redder for sightlines farther from the cluster center. These four results are respectively detected at the 2.3σ, 3.6σ, 7.7σ, and 4.1σ levels. Each of these independent lines of evidence is found to be significant in the cluster outskirts; closer in, the data are more compatible with uniform mixing. Our radial profile is qualitatively consistent with but quantitatively tighter than previous results based on CN absorption. These observations are qualitatively consistent with a scenario wherein a second generation of stars with enhanced helium formed deep within the gravitational potential of a cluster of previous generation stars having more canonical abundances.
dc.publisherIOP Publishing
dc.sourceAstrophysical Journal, The
dc.subjectKeywords: globular clusters: individual: NGC 104 (47 Tuc)
dc.titleThe gradients in the 47 Tuc red giant branch bump and horizontal branch are consistent with a centrally concentrated, helium-enriched second stellar generation
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume736
dc.date.issued2011
local.identifier.absfor020104 - Galactic Astronomy
local.identifier.ariespublicationU3488905xPUB1333
local.type.statusPublished Version
local.contributor.affiliationNataf, David, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationGould, A, Ohio State University
local.contributor.affiliationPinsonneault, Marc H, Ohio State University
local.contributor.affiliationStetson, Peter B, National Research Council of Canada
local.description.embargo2037-12-31
local.bibliographicCitation.issue2
local.bibliographicCitation.startpage94
local.identifier.doi10.1088/0004-637X/736/2/94
dc.date.updated2016-02-24T09:59:13Z
local.identifier.scopusID2-s2.0-80051490589
CollectionsANU Research Publications

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