1. MPIA Student Workshop, Dorio, 2007
The SMC star cluster BS 90
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MPIA Student Workshop, Dorio, 2007

2. Overview - Location of BS 90 - Structural parameters
- Color-magnitude diagram
- Results
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3. The Magellanic Clouds
Location of BS 90
LMC
SMC

4. NGC BS 90 in the SMC
Location of BS 90
NGC 602
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5. Centre of BS 90 10 pc N E - HST/ACS - Three pointings,
Location of BS 90
- HST/ACS
- Three pointings,
centred on NGC 346 E N
10 pc
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6. Structural parameters of BS 90
Structure of BS 90
EFF model
(Elson, Fall & Freeman, 1987):
King model
(King, 1962):
rc : Core radius
rt : Tidal radius
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7. Best-fitting EFF and King model
Structure of BS 90
EFF:
Core radius: rc = 5.57 pc
King:
Core radius: rc = 5.45 pc
Tidal radius: rt = 53.7 pc
Concentration parameter:
c = log(rc/rt) ~ 1.0
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8. Color-magnitude diagram of BS 90
CMD of the BS 90
Area with radius 2 rc E N
10 pc
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9. Subtraction of contaminating stars
CMD of the BS 90
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10. Results from the isochrone fit
CMD of the BS 90
Extinction: AV = 0.04 mag
Distance modulus:
dm = mag
Distance: ~ 58.9 kpc
Age: 4.5 Gyr
Metallicity: Z = 0.004
[Fe/H] ~
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11. Core radius-age relation of the SMC
Results
Age : 4.5 Gyr, Core radius : 5.57 pc
Mackey & Gilmore (2003):
- Lower branch represents
‘standard’ isolated
evolution of a cluster
- Upper right group:
- external influence
- exceptional stellar
population
Triangles: Mackey & Gilmore (2003)
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12. Age-metallicity relation of the SMC
Results
- ‘age gap’ of the LMC
(e.g. Westerlund, 1997;
Rich et al., 2001)
- few old rich clusters in
the SMC
- ~ 10 clusters older
than 4 Gyr
Smith (1999)
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13. (Chemical enrichment models from: Pagel & Tautvaisiene, 1998)
Results
(Chemical enrichment models from: Pagel & Tautvaisiene, 1998)
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14. Further results - Construction of luminosity and mass function
- Radial dependence
of the mass function
slope indicates mass
segregation in BS 90
- The half-mass
relaxation time
(0.95 Gyr) shows
the dynamical origin
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15. Bremen
Und Schluss! !
(?)
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16. Luminosity function
Backup Slides
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17. Radial dependence of the LF
Backup Slides
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18. Mass function
Backup Slides
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