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

Abstract

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. We have obtained optical (3300-6210A) low-resolution spectra of blue massive stars with VLT-FORS2, which we have classified with the aid of Milky Way and Magellanic Cloud standard stars. We have developed the first census of massive blue stars in NGC 55. A study of stellar radial velocities shows agreement with existing HI 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. 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 models.

42 pages, 38 figures. Accepted for publication in A&A

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• A Panchromatic Study of Massive Stars in the Extremely Metal-Poor Local Group Dwarf Galaxy Leo A
• Candidate LBV stars in galaxy NGC 7793 found via HST photometry + MUSE spectroscopy
• Massive stars in the Sagittarius Dwarf Irregular Galaxy
• Discovering new B[e] supergiants and candidate Luminous Blue Variables in nearby galaxies
• A machine-learning photometric classifier for massive stars in nearby galaxies II. The catalog
• High resolution observations of Cen A: Yellow and red supergiants in a region of jet-induced star formation?
• The Future of IMF studies with the ELT and MICADO I: The local Universe as a resolved IMF laboratory