NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-08-18 T02:55:04 PDT
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For refcode 2015MNRAS.451.2625P:
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Copyright by Royal Astronomical Society. 2015MNRAS.451.2625P The SLUGGS survey: combining stellar and globular cluster metallicities in the outer regions of early-type galaxies Pastorello, Nicola; Forbes, Duncan A.; Usher, Christopher; Brodie, Jean P.; Romanowsky, Aaron J.; Strader, Jay; Spitler, Lee R.; Alabi, Adebusola B.; Foster, Caroline; Jennings, Zachary G.; Kartha, Sreeja S.; Pota, Vincenzo Abstract. The outer halo regions of early-type galaxies carry key information about their past accretion history. However, spectroscopically probing the stellar component at such galactocentric radii is still challenging. Using the DEep Imaging Multi-Object Spectrograph on the Keck, we have been able to measure the metallicities of the stellar and globular cluster components in 12 early-type galaxies out to more than 10R_e_. We find similar metallicity gradients for the metal-poor and metal-rich globular cluster subpopulations, suggesting a common formation process for the two subpopulations. This is in conflict with most current theoretical predictions, where the metal-poor globular clusters are thought to be purely accreted and metal-rich globular clusters mostly formed in situ. Moreover, we find that the globular cluster metallicity gradients show a trend with galaxy mass, being steeper in lower mass galaxies than in higher mass galaxies. This is similar to what we find for the outermost galaxy stars and suggests a more active accretion history, with a larger role played by major mergers, in the most massive galaxies. This conclusion is qualitatively consistent with expectations from two-phase galaxy assembly models. Finally, we find that the small difference in metallicity between galaxy stars and metal-rich globular clusters at 1R_e_ may correlate with galaxy mass. The origin of this difference is not currently clear. Key words: galaxies: abundances, galaxies: elliptical and lenticular, cD, galaxies: evolution, galaxies: formation, galaxies: star clusters: general, galaxies: stellar content
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