Keck spectroscopy and imaging of globular clusters in the lenticular galaxy NGC 524

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 [a/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 [a/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 [a/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 x 1011 M ○. (depending on the assumed orbital distribution) interior to ∼2 effective radii of this galaxy.