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 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, Vand 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 þ log (O/ H) ¼ 7:76 AE 0:07 (1 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-matterYdominated dwarf galaxy for observations with the next generation of ground-based extremely large telescopes.