期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 736, 期 2, 页码 -出版社
IOP Publishing Ltd
DOI: 10.1088/2041-8205/736/2/L26
关键词
galaxies: bulges; galaxies: formation; galaxies: halos; galaxies: individual (NGC 3115); galaxies: kinematics and dynamics; globular clusters: general
资金
- W. M. Keck Foundation
- National Science Foundation [AST-0808099, AST-0909237]
- UCSC University Affiliated Research Center
- FONDAP Center for Astrophysics CONICYT [15010003]
- Gordon and Betty Moore Foundation
- Australian Government
- Direct For Mathematical & Physical Scien [0909237, 0808099] Funding Source: National Science Foundation
- Division Of Astronomical Sciences [0909237, 0808099] Funding Source: National Science Foundation
We present a global analysis of kinematics and metallicity in the nearest S0 galaxy, NGC 3115, along with implications for its assembly history. The data include high-quality wide-field imaging from Suprime-Cam on the Subaru telescope, and multi-slit spectra of the field stars and globular clusters (GCs) obtained using Keck-DEIMOS/LRIS and Magellan-IMACS. Within two effective radii, the bulge (as traced by the stars and metal-rich GCs) is flattened and rotates rapidly (v/sigma greater than or similar to 1.5). At larger radii, the rotation declines dramatically to v/sigma similar to 0.7, but remains well aligned with the inner regions. The radial decrease in characteristic metallicity of both the metal-rich and metal-poor GC subpopulations produces strong gradients with power-law slopes of -0.17 +/- 0.04 and -0.38 +/- 0.06 dex dex(-1), respectively. We argue that this pattern is not naturally explained by a binary major merger, but instead by a two-phase assembly process where the inner regions have formed in an early violent, dissipative phase, followed by the protracted growth of the outer parts via minor mergers with typical mass ratios of similar to 15-20:1.
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