Abstract
A major uncertainty in the spectroscopic dating of extragalactic globular clusters concerns the degenerate effect that age and horizontal-branch morphology have on the strength of Balmer lines. In this Letter we show that the ratio between the equivalent widths of HβF and Hβ is far more sensitive to horizontal-branch morphology than to age, thus making it possible to break the degeneracy. We show that it is possible to distinguish intermediateage globular clusters from those whose Balmer lines are strengthened by the presence of blue horizontal-branch stars purely on the basis of the clusters' integrated spectra. The degeneracy between age and horizontal-branch morphology can be lifted with Hβ and HδF line strengths from spectra with S/N ≳ 30 Å-1, which is typical of current studies of integrated spectroscopy of extragalactic globular clusters.
Original language | English (US) |
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Pages (from-to) | L33-L36 |
Journal | Astrophysical Journal |
Volume | 608 |
Issue number | 1 II |
DOIs | |
State | Published - Jun 10 2004 |
Externally published | Yes |
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
Keywords
- Galaxies: evolution
- Galaxies: stellar content
- Globular clusters: general
- Stars: evolution
- Stars: horizontal-branch