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Globular Clusters with Gemini

Globular Clusters with Gemini. Duncan Forbes Swinburne University. Mike Beasley (Lick Obs), Terry Bridges (Queen’s University) Duncan Forbes (Swinburne) Favio Feifer, Juan Forte (Argentina) Karl Gebhardt (Texas) Dave Hanes (Queen’s University) Steve Zepf (Michigan)

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Globular Clusters with Gemini

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  1. Globular Clusters with Gemini Duncan Forbes Swinburne University Mike Beasley (Lick Obs), Terry Bridges (Queen’s University) Duncan Forbes (Swinburne) Favio Feifer, Juan Forte (Argentina) Karl Gebhardt (Texas) Dave Hanes (Queen’s University) Steve Zepf (Michigan) Ray Sharples (Durham)

  2. Science Goals Long term spectroscopic study of the globular cluster systems of early-type galaxies using the Gemini Multi-Object Spectrographs on the Gemini-North and Gemini-South telescopes. Key science goals: • test specific galaxy formation scenarios (e.g. mergers versus monolithic collapse) • test GC formation scenarios (e.g. presence of young GCs, abundance ratio variations) • investigate possible angular momentum transfer during merging and determine the specific angular momentum of ellipticals • probe dark matter mass distributions out to large radii

  3. International Collaboration Large Gemini program since 2002A Publicity in local newspapers and ABC Radio Pros: Same GMOS instrument North and South Photometry and spectra Cons: Proposal (deadline, PIT, 1 vs 2, abstract, sci case, attachments etc) Manpower limited (1 paper to date)

  4. Gemini Strategy Obtain colours, magnitudes, kinematics, metal abundances, abundance ratios  and ages for several hundred GCs associated with elliptical (E) and lenticular (S0) galaxies in a range of environments. Gemini 8m vs Keck 10m GC kinematics GC ages

  5. Sample Selection GalaxyTypeMVEnvironment NGC 4649 E2 -22.4 Cluster NGC 3379 E1 -20.7 Group NGC 524 S0 -22.6 Group NGC 7332 S0 -20.1 Field NGC 4374 E2 -22.1 Cluster NGC 3115 S0 -20.8 Field NGC 3923 E4 -21.9 Group IC 1459 E3 -21.4 Group

  6. GMOS Data To Date GalaxyPhotometrySpectroscopy NGC 46493 fields: g,i 1 field: 10 hr NGC 33793 fields: g,r,i 1 field: 10 hr NGC 5243 fields: g,r,i 2 fields: 6.5, 8 hr NGC 73323 fields: g,r,i 2 fields: 8, 8 hr

  7. NGC 4649 (M60) Virgo cluster, E2, MV= -22.4, D=16 Mpc 480 sec in g’, i’ for 3 fields Forbes et al 2004, MNRAS submitted

  8. Spatial Location | 8.4 arcmin (40 kpc) | X

  9. Colour-Magnitude Diagrams

  10. Colours: All Clusters NGC 4649 (45-240 arcsec) Blue: (g-i)'=0.87 Red: (g-i)'=1.17 i'<23.5 N=995 90% complete

  11. Colours: By Radius

  12. Colour & Density Profiles Galaxy Galaxy Red All Blue

  13. GC Luminosity Function i’TO = 23.2 +/- 0.15 NTotal = 3700 +/- 900 SN = 4.1 +/- 1.0

  14. NGC 3379 Leo Group, E1, MV= -20.7, D=10 Mpc 10 hours total exposure B600 grism: ~5 Å FWHM with 1” slit 4000-7000 Å typical coverage Beasley et al. 2004, in prep

  15. Cluster Ages/Metallicities

  16. Cluster Dynamics

  17. Cluster Dynamics 11 kpc

  18. Summary • GMOS is a powerful way to study GC systems photometrically and spectroscopically • Photometry: GC colours, luminosity functions, density profiles for blue/red GCs • Spectroscopy yields GC ages, metallicities, abundance ratios, kinematics, host galaxy M/L ratios • Interesting results already from existing sample; long-term goal is to obtain data for ~10 galaxies, covering range of galaxy luminosity and environment

  19. Globular Clusters…may hold the key to understanding the evolution of galaxies and ultimately the Universe. (New Scientist Nov. 2002)

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