The ARAUCARIA Project: VLT‐FORS Spectroscopy of Blue Supergiants in NGC 3109—Classifications, First Abundances, and Kinematics

Abstract

We have obtained multiobject spectroscopy of luminous blue supergiantsin NGC 3109, a galaxy at the periphery of the Local Group at ~1.3 Mpc.We present a detailed catalog including finding charts, V and Imagnitudes, spectral classifications, and stellar radial velocities. Theradial velocities are seen to trace the rotation curves obtained fromstudies of the H I gas. From quantitative analysis of eight B-typesupergiants we find a mean oxygen abundance of 12+log(O/H)=7.76+/-0.07(1 {$σ$} systematic uncertainty), with a median result of 7.8. Givenits distance, we highlight NGC 3109 as the ideal example of alow-metallicity, dark-matter-dominated dwarf galaxy for observationswith the next generation of ground-based extremely large telescopes.Based on observations at the European Southern Observatory Very LargeTelescope in program 171.D-0004.