The SMC star cluster BS 90
description
Transcript of The SMC star cluster BS 90
MPIA Student Workshop, Dorio, 2007
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The SMC star cluster BS 90
MPIA Student Workshop, Dorio, 2007
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MPIA Student Workshop, Dorio, 2007
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Overview
- Location of BS 90
- Structural parameters
- Results
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- Color-magnitude diagram
MPIA Student Workshop, Dorio, 2007
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SMC
LMC
The Magellanic CloudsLocation of BS
90
MPIA Student Workshop, Dorio, 2007
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NGC 346 + BS 90 in the SMC
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Location of BS
90
NGC 602
MPIA Student Workshop, Dorio, 2007
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10 pc E
N
Location of BS
90
- HST/ACS
- Three pointings, centred on NGC 346
Centre of BS 90
MPIA Student Workshop, Dorio, 2007
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Structure of BS
90
fieldfarfrf 2220 )1()(
212 )12( arc
EFF model(Elson, Fall & Freeman, 1987):
2212212]
))(1(
1
))(1(
1[)(
ctc rrrrrf
King model(King, 1962):
rc : Core radius
rt : Tidal radius
Structural parameters of BS 90
MPIA Student Workshop, Dorio, 2007
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Best-fitting EFF and King model
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EFF:
Core radius: rc = 5.57 pc
Structure of BS
90
King:
Core radius: rc = 5.45 pc
Tidal radius: rt = 53.7 pc
Concentration parameter:
c = log(rc/rt) ~ 1.0
MPIA Student Workshop, Dorio, 2007
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Color-magnitude diagram of BS 90CMD of
the BS 90
10 pc E
N
Area with radius 2 rc
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Subtraction of contaminating starsCMD of
the BS 90
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Age: 4.5 Gyr
Metallicity: Z = 0.004
[Fe/H] ~ - 0.72
Extinction: AV = 0.04 mag
Distance modulus:dm = 18.85 mag
Distance: ~ 58.9 kpc
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Results from the isochrone fitCMD of
the BS 90
MPIA Student Workshop, Dorio, 2007
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Results
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Triangles: Mackey & Gilmore (2003)
Core radius-age relation of the SMC
Age : 4.5 Gyr, Core radius : 5.57 pc
- Lower branch represents ‘standard’ isolated evolution of a cluster
- Upper right group: - external influence - exceptional stellar population
Mackey & Gilmore (2003):
MPIA Student Workshop, Dorio, 2007
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- ‘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
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Smith (1999)
Age-metallicity relation of the
SMCResults
MPIA Student Workshop, Dorio, 2007
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Results
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(Chemical enrichment models from: Pagel & Tautvaisiene, 1998)
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- Construction of luminosity and mass function
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Further resultsResults
- 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
MPIA Student Workshop, Dorio, 2007
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Und Schluss!
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Bremen
!(?)
MPIA Student Workshop, Dorio, 2007
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Luminosity functionBacku
p Slides
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MPIA Student Workshop, Dorio, 2007
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Radial dependence of the LFBacku
p Slides
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MPIA Student Workshop, Dorio, 2007
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Mass functionBacku
p Slides
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