The structure of the Magellanic Clouds traced by red clump stars at near-infrared wavelengths

Abstract

This thesis is about the Red Clump (RC) star population within the Magellanic Clouds. These are observed in the near-infrared Y JKs wavelengths using data obtained by the ESO public VMC survey. These were studied to shed more light on the internal structure and past and current evolution of this interacting system of dwarf irregular galaxies.

RC stars were selected from the colour magnitude diagram (CMD) using a contour method to assign the selection box and reddening vector. The J - Ks vs Ks CMD of the central 30 Doradus region of the Large Magellanic Cloud (LMC) region was analysed to determine the extinction content there, producing a reddening map. This was compared with other works including an optical reddening map which also used RC stars. The reddening map also proved to be a useful tool as a tracer of ISM features including the identification of molecular clouds.

The extinction maps were made in the Y - Ks colours for the whole LMC and whole SMC. These were then used to deredden the populations. These populations had their distribution examined in a number of ways including line of sight depth and residuals derived from least-squares plane fitting. The distorted structures found appear to be the product of interactions between the LMC and SMC.

RC content was also studied in the Magellanic Bridge region (lying between the LMC and SMC) where a RC population was found throughout the Bridge, mainly at LMC distance and mostly towards the LMC and SMC showing evidence of a tidally stripped SMC population. Maps were created showing this.

This thesis thus presents an unprecedented, global view of the stellar and interstellar structure of the interacting Magellanic Cloud, using an intermediate-age stellar tracer, piercing through and using dust.