The Araucaria Project: VLT-spectroscopy of blue massive stars in NGC 55 ^*,**

¹ Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain e-mail: norberto@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, Avda. Astrofísico Francisco Sánchez s/n, 38071 La Laguna, Tenerife, Spain
³ Astronomy Research Centre, Department of Physics & Astronomy, School of Mathematics & Physics, The Queen's University of Belfast, Belfast, Northern Ireland, UK
⁴ Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
⁵ Departamento de Física, Astronomy Group, Universidad de Concepción, Casilla 160-C, Concepción, Chile
⁶ Warsaw University Observatory, Al. Ujazdowskie 4, 00-478, Warsaw, Poland
⁷ Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA

Received: 15 January 2008
Accepted: 31 March 2008

Abstract

Aims. This is the first paper of a series devoted to studying the population of blue massive stars in NGC 55, a galaxy of the Sculptor group at a distance of about 2 Mpc.

Methods. We have obtained optical ( Å), low-resolution spectra of approximately 200 blue massive stars with VLT-FORS2, which we have classified with the aid of Milky Way and Magellanic Cloud standard stars.

Results. We present the first census of massive blue stars in NGC 55. A study of stellar radial velocities shows agreement with existing  rotational velocity curve work and reveals the presence of one object with peculiar velocity. A qualitative study of the stellar metallicity suggests that its global distribution over NGC 55 is close to that of the LMC, as derived from previous studies.

Conclusions. We present a catalogue with 164 classifications of blue massive stars in NGC 55. This catalogue is a first and necessary step for the subsequent quantitative study of blue massive stars in NGC 55 with state-of-the-art model atmospheres.