Keck Spectroscopy of Young and Old Star Clusters in NGC 1023

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Abstract
We present Keck/LRIS spectra for 11 old globular clusters in the S0-type galaxy NGC 1023 and two young blue clusters in the nearby companion NGC 1023A. Analysis of the spectra of seven old clusters with sufficient signal-to-noise ratio shows generally good agreement between spectroscopic and previous photometric metallicity estimates, but the integrated colors of two clusters are too blue for their spectroscopic metallicities. Although the cluster ages are not well constrained, they are most likely similar to those of Milky Way globular clusters and certainly older than ~5 Gyr. The brightest globular cluster in the sample shows enhanced cyanogen, possibly indicating an abundance anomaly similar to that observed in some M31 globular clusters. For the two blue clusters in NGC 1023A we estimate ages between 125 and 500 Myr on the basis of their strong Balmer lines. The total masses are about 8 × 104 M⊙ and 6 × 104 M⊙ for a Miller-Scalo initial mass function and Z = 0.004, making these objects similar to the young populous clusters in the Large Magellanic Cloud. It is suggested that the two young clusters might have formed during a period of enhanced star formation activity in NGC 1023A, stimulated by a close encounter with NGC 1023.
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