The ARAUCARIA Project: VLT-FORS spectroscopy of blue supergiants in NGC 3109 - Classifications, first abundances and kinematics

C. J. Evans (1), F. Bresolin (2), M. A. Urbaneja (2), G. Pietrzynski (3,4), W. Gieren (3), R.-P. Kudritzki (2)

(1) UK Astronomy Technology Centre, Edinburgh;
(2) Institute for Astronomy, Hawaii;
(3) Universidad de Conception, Chile;
(4) Warsaw University Observatory, Poland.

We have obtained multi-object 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 HI 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-sigma 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 (ELTs).

Reference: Accepted by ApJ, astro-ph/0612114
Status: Manuscript has been accepted