CCD CT1 photometry of small angular size candidate star clusters projected on to crowded Small Magellanic Cloud star fields

A.E. PIATTI, E. BICA

Bol. Asoc. Arg. Astron.

AAA Editorial board

Año: 2012 vol. 55 p. 143 - 146

0571?3285

              We present for the first time CCD CT1 photometry for 11unstudied or poorly studied candidate star clusters. The selected objectsare of small angular size, contain a handful of stars, and are projectedtowards the innermost regions of the Small Magellanic Cloud (SMC). Toclean their Colour-Magnitude Diagrams (CMDs) from the unavoidablestar field contamination, we use a method which has shown to be able toeliminate stochastic effects in the cluster CMDs caused by the presenceof isolated bright stars, as well as, to make a finer cleaning in the mostpopulous CMD regions. The resulting cleaned cluster CMDs suggest thatmost of the studied candidate star clusters would not appear to be gen-uine physical systems. Furthermore, we confirm that the ages previouslyderived for some of them mostly reflect those of the composite stellarpopulations of the SMC field. On the other hand, if we use the spatialdistribution of possible non-clusters to statiscically decontaminate thatof the cataloged clusters, we find that there is no clear difference betweenthe expected and the observed cluster spatial distributions. However, ifwe double the amount of possible non-clusters the difference becomes big-ger than 2σ between a ≈ 0.3◦ and 1.2◦ (a = the semi-major axis of anellipse parallel to the SMC bar and with b/a = 1/2).