The Araucaria Project: VLT-spectroscopy of blue massive stars in NGC 55 (original) (raw)

A&A 485, 41-50 (2008)

1,2, A. Herrero1,2, M. Garcia1, C. Trundle3, F. Bresolin4, W. Gieren5, G. Pietrzyński5,6, R.-P. Kudritzki4 and R. Demarco7

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.

Key words: galaxies: individual: NGC 55 / galaxies: stellar content / stars: early-type / stars: fundamental parameters / catalogs

*

Based on observations obtained at the ESO VLT for Large Programme 171.D-0004.

**

Appendices A–C are only available in electronic form at http://www.aanda.org