MPIA Student Workshop, Dorio, 2007 The SMC star cluster BS 90 Boyke Rochau MPIA Student Workshop, Dorio, 2007

Overview - Location of BS 90 - Structural parameters - Color-magnitude diagram - Results Boyke Rochau

The Magellanic Clouds Location of BS 90 LMC SMC

NGC 346 + BS 90 in the SMC Location of BS 90 NGC 602 Boyke Rochau

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 Boyke Rochau

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 Boyke Rochau

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 Boyke Rochau

Color-magnitude diagram of BS 90 CMD of the BS 90 Area with radius 2 rc E N 10 pc Boyke Rochau

Subtraction of contaminating stars CMD of the BS 90 Boyke Rochau

Results from the isochrone fit CMD of the BS 90 Extinction: AV = 0.04 mag Distance modulus: dm = 18.85 mag Distance: ~ 58.9 kpc Age: 4.5 Gyr Metallicity: Z = 0.004 [Fe/H] ~ - 0.72 Boyke Rochau

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) Boyke Rochau

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) Boyke Rochau

(Chemical enrichment models from: Pagel & Tautvaisiene, 1998) Results (Chemical enrichment models from: Pagel & Tautvaisiene, 1998) Boyke Rochau

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 Boyke Rochau

Bremen Und Schluss! ! (?) Boyke Rochau

Luminosity function Backup Slides Boyke Rochau

Radial dependence of the LF Backup Slides Boyke Rochau

Mass function Backup Slides Boyke Rochau