Bibcode
Beasley, Michael A.; Forbes, Duncan A.; Brodie, Jean P.; Kissler-Patig, Markus
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 347, Issue 4, pp. 1150-1163.
Fecha de publicación:
2
2004
Número de citas
23
Número de citas referidas
20
Descripción
We have obtained Keck Low-Resolution Imaging Spectrometer imaging and
spectra for 29 globular clusters associated with the lenticular galaxy
NGC 524. Using the empirical calibration of Brodie & Huchra we find
that our spectroscopic sample spans a metallicity range of -2.0
<=[Fe/H]<= 0. We have compared the composite spectrum of the
metal-poor ([Fe/H] < -1) and metal-rich clusters with stellar
population models in order to estimate the ages of the NGC 524 globular
clusters. We conclude that the clusters are generally old, and are
coeval at the 2σ confidence level. To determine the mean
[α/Fe] ratios of the globular clusters, we have employed the
Milone et al. α-enhanced stellar population models. We verified
the reliability of these models by comparing them with high
signal-to-noise Galactic globular cluster spectra. We observe a weak
trend of decreasing [α/Fe] ratios with increasing metallicity in
the NGC 524 clusters; the metal-poor clusters possess [α/Fe]~0.3,
whilst the metal-rich clusters exhibit [α/Fe] ratios closer to
solar-scaled values. Analysis of the cluster system kinematics reveals
that the full sample (excluding an outlying cluster) exhibits a rotation
of 114 +/- 60 km s-1 around a position angle of 22°+/-
27°, and a velocity dispersion of 186 +/- 29 km s-1 at a
mean radius of 89 arcsec from the galaxy centre. Subdividing the
clusters into metal-poor and metal-rich subcomponents (at [Fe/H]=-1.0),
we find that the metal-poor (17) clusters and metal-rich (11) clusters
have similar velocity dispersions (197 +/- 40 and 169 +/- 47 km
s-1, respectively). However, the metal-poor clusters dominate
the rotation in our sample with 147 +/- 75 km s-1, whilst the
metal-rich clusters show no significant rotation (68 +/- 84 km
s-1). We derive a virial and projected mass estimation for
NGC 524 of between 4 and 13 × 1011 Msolar
(depending on the assumed orbital distribution) interior to ~2 effective
radii of this galaxy.