The Detailed Chemical Properties of M31 Star Clusters I. Fe, Alpha and Light Elements

Abstract

We present ages, [Fe/H] and abundances of the alpha elements Ca I, Si I, Ti I, Ti II, and light elements Mg I, Na I, and Al I for 31 globular clusters in M31, which were obtained from high resolution, high signal-to-noise ratio (SNR$>60$) echelle spectra of their integrated light. All abundances and ages are obtained using our original technique for high resolution integrated light abundance analysis of globular clusters. This sample provides a never before seen picture of the chemical history of M31. The globular clusters are dispersed throughout the inner and outer halo, from 2.5 kpc $<$ R${}_{M31}$ $<$ 117 kpc. We find a range of [Fe/H] within 20 kpc of the center of M31, and a constant [Fe/H]$\sim -1.6$ for the outer halo clusters. We find evidence for at least one massive globular cluster in M31 with an age between 1 and 5 Gyr. The alpha-element ratios are generally similar to Milky Way globular cluster and field star ratios. We also find chemical evidence for a late-time accretion origin for at least one cluster, which has a different abundance pattern than other clusters at similar metallicity. We find evidence for star-to-star abundance variations in Mg, Na, and Al in the globular clusters in our sample, and find correlations of Ca, Mg, Na, and possibly Al abundance ratios with cluster luminosity and velocity dispersion, which can potentially be used to constrain globular cluster self-enrichment scenarios. Data presented here were obtained with the HIRES echelle spectrograph on the Keck I Telescope.

Accepted for publication in ApJ, proof corrections applied

References in corpus (19)

• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• Origin of multiple stellar populations in globular clusters and their helium enrichment
• Multiple stellar populations in Magellanic Clouds clusters. I. An ordinary feature for intermediate age globulars in the LMC?
• Looking outside the Galaxy: the discovery of chemical anomalies in 3 old Large Magellanic Cloud clusters
• VLT/UVES Spectroscopy of Individual Stars in Three Globular Clusters in the Fornax Dwarf Spheroidal Galaxy
• A Large Stellar Evolution Database for Population Synthesis Studies. III. Inclusion of the full Asymptotic Giant Branch phase and Web tools for stellar population analyses
• Measuring Ages and Elemental Abundances from Unresolved Stellar Populations: Fe, Mg, C, N, and Ca
• The Bizarre Chemical Inventory of NGC 2419, An Extreme Outer Halo Globular Cluster
• Globular Cluster Systems in Giant Ellipticals: the Mass/Metallicity Relation
• The outer halo globular cluster system of M31 - I. The final PAndAS catalogue
• Structural parameters for globular clusters in M31 and generalizations for the fundamental plane
• The outer halo globular cluster system of M31 - II. Kinematics
• Globular Cluster Abundances from High-Resolution Integrated Light Spectra, I: 47 Tuc
• Reddening, Colour and Metallicity of the M31 Globular Cluster System
• ACS photometry of newly-discovered globular clusters in the outer halo of M31
• On The Origin of the Blue Tilt in Extragalactic Globular Cluster Systems
• The Outer Halo Globular Clusters of M31
• Optimal Integrated Abundances for Chemical Tagging of Extragalactic Globular Clusters
• Probing the Intermediate-Age Globular Clusters in NGC 5128 from Ultraviolet Observations

Cited by in corpus (1)

• Integrated Light Chemical Tagging Analyses of Seven M31 Outer Halo Globular Clusters from the Pan-Andromeda Archaeological Survey