Analysis of colour-magnitude diagrams of rich LMC clusters: NGC 1831
TLDR
In this paper, the analysis of a deep colour-magnitude diagram (CMD) of NGC 1831, a rich star cluster in the LMC, is presented.Abstract:
We present the analysis of a deep colour-magnitude diagram (CMD) of NGC 1831, a rich star cluster in the LMC. The data were obtained with HST/WFPC2 in the F555W (V) and F814W (I) filters, reaching m555 25. We discuss and apply a method of correcting the CMD for sampling incompleteness and field star contamination. Ecient use of the CMD data was made by means of direct comparisons of the observed to model CMDs. The model CMDs are built by an algorithm that generates artificial stars from a single stellar population, characterized by an age, a metallicity, a distance, a reddening value, a present day mass function and a fraction of unresolved binaries. Photometric uncertainties are empirically determined from the data and incorporated into the models as well. Statistical techniques are presented and applied as an objective method to assess the compatibility between the model and data CMDs. By modelling the CMD of the central region in NGC 1831 we infer a metallicity Z = 0:012, 8:75 log (=yr) 8:80, 18:54 (m M)0 18:68 and 0:00 E(B V) 0:03. For the position dependent PDMF slope (= dl og(M)= dl ogM), we clearly observe the eect of mass segregation in the system: for projected distances R 30 arcsec,' 1:7, whereas 2:2 2:5 in the outer regions of NGC 1831.read more
Citations
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