Abstract

Blue Massive Stars Beyond the Milky Way

Norberto Castro Rodriguez (National Observatory of Athens, Greece)

A. Herrero(1,2), M. A. Urbaneja(3), M. Garcia(1,2), S. Simon-Diaz(1,2), F. Bresolin(3), G. Pietrzynski(4,5), R. -P. Kudritzki(3), W. Gieren(4) 1.- Instituto de Astrofisica de Canarias 2.- Dept. de Astrofisica, Universidad de La Laguna 3.- Institute for Astronomy, University of Hawaii 4.- Departamento de Astronomia, Universidad de Concepcion 5.-Warsaw University Observatory

Massive blue stars are the rarest in number compared with other stars, nevertheless they are the main engines in the chemical and dynamical evolution of the Universe. They are also among the brightest objects, a property that gives the opportunity to study them in detail beyond the Milky Way boundaries. This property has allowed us to develop the first census of blue massive stars in the galaxy NGC 55, which is ~1.9 Mpc away. In spite of the large distance it was possible to perform a detailed study on the largest subset of massive blue objects ever analyzed at such a distance. The results not only yielded a characterization of the stars: stellar parameters, chemical abundances, physical parameters (mass, radius and luminosity), but also information about their evolution. Even so, they allowed us to derive important properties of the host galaxy, as well as the dynamical structure and chemical distribution along NGC 55.