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

We have obtained multiobject spectroscopy of luminous blue supergiants in 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 I magnitudes, spectral classifications, and stellar radial velocities. The radial velocities are seen to trace the rotation curves obtained from studies of the H I gas. From quantitative analysis of eight B-type supergiants 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. Given its distance, we highlight NGC 3109 as the ideal example of a low-metallicity, dark-matter-dominated dwarf galaxy for observations with the next generation of ground-based extremely large telescopes.