Vazdekis, A.; Salaris, Maurizio; Arimoto, Nobuo; Rose, James A.
Referencia bibliográfica
The Astrophysical Journal, Volume 549, Issue 1, pp. 274-280.
Fecha de publicación:
3
2001
Revista
Número de citas
65
Número de citas referidas
50
Descripción
We investigate current problems in obtaining reliable ages for old
stellar systems based on stellar population synthesis modeling of their
integrated spectra. In particular, we address the large ages derived for
the globular cluster 47 Tuc, which is at odds with its color-magnitude
diagram (CMD) age. Using a new age indicator,
Hγσ<130, which is particularly effective at
breaking the degeneracy between age and metallicity, we confirm the
discrepancy between the spectroscopic age and the CMD age of 47 Tuc, in
that the spectroscopic age is much older. Nebular emission appears
unlikely to be a source for weakening the observed Balmer lines. We then
explore a number of key parameters affecting the temperature of turnoff
stars, which are the main contributors to the Balmer lines for old
metal-rich stellar populations. We find that α-enhanced isochrones
with atomic diffusion included not only provide a good fit to the CMD of
47 Tuc but also lead to a spectroscopic age in better agreement with the
CMD age.