# 세줄 요약 #
- We present new wide-field photometry and spectroscopy of the globular clusters (GCs) around NGC 4649 (M60), the third brightest galaxy in the Virgo cluster.
- We confirm significant GC colour bimodality and find that the red GCs are more centrally concentrated, while the blue GCs are more spatially extended.
- We find that formation via a major merger between two gas-poor galaxies, followed by satellite accretion, can consistently reproduce the observations of NGC 4649 at different radii.
# 상세 리뷰 #
1. Photometric study of NGC4649
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- HST/ACS, CFHT/MegaCam, Subaru/Suprime-Cam
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- GC color bimodality
- The red GCs: more centrally concentrated
- The blue GCs: more spatially extended
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- color gradient
- A negative GC color gradients in the innermost 20 kpc
- A flat gradients out to large radii
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2. Spectroscopic study of NGC 4649
- Keck/DEIMOS, Gemini/GMOS, MMT/Hectospec
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- Confirmed 431 GCs catalog
- A factor of 3.5 larger than previous data sets
- A factor of 3 improvements in velocity precision.
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- Spectroscopy result
- Significant rotation at all radii
- Counter-rotating Subgroups
- Bumpy velocity dispersion
- all result meaning -> major merger?
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3. Formation scenarios of NGC 4649
- Stage 1. Dry major merger -> Stage 2. Satellite accretion
- Spiral galaxy gas stripping -> Elliptical galaxy [S0 type]
- but non-detection primordial disc
- no strong evidence: interacting with neighboring NGC 4647
* Reference: Pota, V., “A SLUGGS and Gemini/GMOS combined study of the elliptical galaxy M60: wide-field photometry and kinematics of the globular cluster system”, [Monthly Notices of the Royal Astronomical Society], vol. 450, no. 2, pp. 1962–1983, 2015. doi:10.1093/mnras/stv677.
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