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)

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

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)

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

Sample Selection Galaxy Type MV Environment 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

GMOS Data To Date Galaxy Photometry Spectroscopy NGC 4649 3 fields: g,i 1 field: 10 hr NGC 3379 3 fields: g,r,i 1 field: 10 hr NGC 524 3 fields: g,r,i 2 fields: 6.5, 8 hr NGC 7332 3 fields: g,r,i 2 fields: 8, 8 hr

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

Spatial Location | 8.4 arcmin (40 kpc) | X

Colour-Magnitude Diagrams

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

Colours: By Radius

Colour & Density Profiles Galaxy Galaxy Red All Blue

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

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

Cluster Ages/Metallicities

Cluster Dynamics

Cluster Dynamics 11 kpc

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

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