C. Martayan Abstract

Spectroscopic Survey of H-alpha Emission-Line Stars of the Magellanic Clouds

C. Martayan (ESO), D. Baade, G. Aguayo, H. Garrido, and J. Fabregat

The ESO Wide Field Imager at the 2.2m of La Silla was used with its slitless facility to do a survey of the H-alpha emission-line stars in the Magellanic Clouds and in 2 Galactic open clusters.  About 8 million spectra were obtained in the LMC and SMC in less than 2 nights showing that the WFI in slitless mode was an efficient instrument for such kind of spectroscopic survey.

First, we will describe the observations, the data reduction, and analysis processes of this specific mode of WFI imagers with examples from the obtained Galactic and Magellanic observations. Second, we will present the results with the WFI-slitless survey in about 80 SMC open clusters of the ELS search, with a special emphasis on Be stars. The comparison of Be stars frequency among early B stars populations show that they are 3 to 5 times more abundant in the SMC than in the Galaxy. This result is consistent with the metallicity gradient between those 2 galaxies, leading to faster rotational velocities and therefore to more Be stars in the SMC.