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Home List of Titles The SLUGGS survey: NGC3115, a critical test case for metallicity bimodality in globular cluster systems
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/238068
- The SLUGGS survey: NGC3115, a critical test case for metallicity bimodality in globular cluster systems
- Brodie, Jean P.; Usher, Christopher; Conroy, Charlie; Strader, Jay; Arnold, Jacob A.; Forbes, Duncan A.; Romanowsky, Aaron J.
- Due to its proximity (9 Mpc) and the strongly bimodal color distribution of its spectroscopically well-sampled globular cluster (GC) system, the early-type galaxy NGC3115 provides one of the best available tests of whether the color bimodality widely observed in GC systems generally reflects a true metallicity bimodality. Color bimodality has alternatively been attributed to a strongly nonlinear color-metallicity relation reflecting the influence of hot horizontal-branch stars. Here, we couple Subaru Suprime-Cam gi photometry with Keck/DEIMOS spectroscopy to accurately measure GC colors and a CaT index that measures the Ca II triplet. We find the NGC3115 GC system to be unambiguously bimodal in both color and the CaT index. Using simple stellar population models, we show that the CaT index is essentially unaffected by variations in horizontal-branch morphology over the range of metallicities relevant to GC systems (and is thus a robust indicator of metallicity) and confirm bimodality in the metallicity distribution. We assess the existing evidence for and against multiple metallicity subpopulations in early- and late-type galaxies and conclude that metallicity bi/multimodality is common. We briefly discuss how this fundamental characteristic links directly to the star formation and assembly histories of galaxies.
- Publication type
- Journal article
- Research centre
- Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing
- Astrophysical Journal Letters, Vol. 759, no. 2 (Nov 2012), article no. L33
- Publication year
- FOR Code(s)
- 0201 Astronomical and Space Sciences
- Galaxies; Globular clusters; NGC 3115; Star clusters
- Institute of Physics Publishing
- Publisher URL
- Copyright © 2012 The American Astronomical Society. All rights reserved. The American Astronomical Society does not allow institutions to archive either the accepted manuscript or the published version of the article. However, you can find an earlier version of the full text here: http://arxiv.org/abs/1209.5390
- Additional information
- The authors acknowledge support from the NSF through grants AST-0808099, AST-0909237, and AST-1109878.
- Peer reviewed