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

MPIA Student Workshop, Dorio, 2007

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Subtraction of contaminating starsCMD of

the BS 90

MPIA Student Workshop, Dorio, 2007

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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)

MPIA Student Workshop, Dorio, 2007

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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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