Globular Clusters with Gemini

1
Globular Clusters with Gemini
Duncan Forbes Swinburne University
Mike Beasley (Lick Obs), Terry Bridges (Queens
University) Duncan Forbes (Swinburne) Favio
Feifer, Juan Forte (Argentina) Karl Gebhardt
(Texas) Dave Hanes (Queens 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

• 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

6
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

7
NGC 4649 (M60)

• Virgo cluster, E2, MV -22.4, D16 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' 11
Colours By Radius
12
Colour Density Profiles
Galaxy
Galaxy
Red
All
Blue
13
GC Luminosity Function
iTO 23.2 /- 0.15 NTotal 3700 /- 900 SN
4.1 /- 1.0
14
NGC 3379

• Leo Group, E1, MV -20.7, D10 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
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
Cluster Ages/Metallicities
19
Cluster Dynamics
20
Cluster Dynamics
11 kpc
21
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

22
Globular Clustersmay hold the key to
understanding the evolution of galaxies and
ultimately the Universe. (New Scientist Nov. 2002)