Light-element abundance variations at low metallicity: The globular cluster NGC 5466

Matthew Shetrone, Sarah L. Martell, Rachel Wilkerson, Joshua Adams, Michael H. Siegel, Graeme H. Smith, Howard E. Bond

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

We present low-resolution (R ≃ 850) spectra for 67 asymptotic giant branch (AGB), horizontal branch, and red giant branch (RGB) stars in the low-metallicity globular cluster NGC 5466, taken with the VIRUS-P integral-field spectrograph at the 2.7 m Harlan J. Smith telescope at McDonald Observatory. Sixty-six stars are confirmed, and one rejected, as cluster members based on radial velocity, which we measure to an accuracy of 16 km s-1 via template-matching techniques. CN and CH band strengths have been measured for 29 RGB and AGB stars in NGC 5466, and the band-strength indices measured from VIRUS-P data show close agreement with those measured from Keck/LRIS spectra previously taken for five of our target stars. We also determine carbon abundances from comparisons with synthetic spectra. The RGB stars in our data set cover a range in absolute V magnitude from +2 to -3, which permits us to study the rate of carbon depletion on the giant branch as well as the point of its onset. The data show a clear decline in carbon abundance with rising luminosity above the luminosity function "bump" on the giant branch, and also a subdued range in CN band strength, suggesting ongoing internal mixing in individual stars but minor or no primordial star-to-star variation in light-element abundances.

Original languageEnglish (US)
Pages (from-to)1119-1127
Number of pages9
JournalAstronomical Journal
Volume140
Issue number4
DOIs
StatePublished - Oct 1 2010

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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