The 3D structure and stellar content of the outer parts of the small magellanic cloud

Abstract

This study is directed towards investigating the structure and stellar content of the Small Magellanic Cloud (SM C), the second nearest external galaxy, with the aim of understanding its evolutionary development in the context of its interactions with the Large Magellanic Cloud and our own Galaxy. The study extends the work done by D. Hatzidimitriou on the north-eastern and south-western parts of the SMC, which was presented in her PhD thesis (1988), to cover the rest of the outer area lying beyond about 2 kpc from the SMC centre.

Including the plate material utilised by D. Hatzidimitriou, the observational material for this project consists of 38 good quality blue and red photographic plates taken with the UK Schmidt Telescope in Australia. The plates were digitised by the COSMOS automatic measuring machine and calibrated by CCD sequences obtained at the Danish 1.5-m telescope at ESO in Chile. The resulting database consists of positional and colour-magnitude data for 1.1 million objects covering nearly the whole of the outer area of the SMC.

The scientific analysis involved the study of the properties of colour-magnitude diagrams in conjunction with surface distribution plots of different stellar populations in order to derive the detailed positional dependence of the line-of-sight depth and the past star formation history of the outer parts of the SMC. This has led to confirmation that the depth o f the SMC exceeds its tidal radius in the eastern projected areas and supports current ideas suggesting the disintegration of the SMC.