Duncan A. Forbes(1), Michael A. Beasley(1), Jean P. Brodie(2), Markus Kissler-Patig(3)
Affiliation
(1)Astrophysics & Supercomputing, Swinburne University, Hawthorn, VIC 3122, Australia, (2)Lick Observatory, University of California, Santa Cruz, CA 95064, USA (3) European Southern Observatory, Germany
Accepted by
ApJL
Contact
URL
Links
Abstract
We present high signal-to-noise Keck spectra for 10 globular
clusters associated with the giant Fornax elliptical NGC 1399,
and compare measured line indices with current stellar population
models.
Our data convincingly demonstrate, for the first time,
that at least some of the clusters in a giant elliptical galaxy
have super-solar abundance ratios, similar to the host galaxy.
From Hß line-strengths the majority of
clusters have ages of ~11 Gyrs (within 2sigma), which is
similar to the luminosity-weighted stellar age of
NGC 1399.
Two of the clusters
(which also reveal enhanced abundance ratios)
show significantly higher Hß values than the
others. It remains unclear whether this is due to
young (~2 Gyr) ages, or extremely old (> 15
Gyr) ages with a warm blue horizontal branch. However a conflict with
current cosmological parameters is avoided if the young age is
favored.
Either alternative indicates a complicated age distribution among
the metal-rich clusters and sets interesting
constraints on their chemical enrichment
at late epochs.