Stellar Spectroscopy Far Beyond the Local Group

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Abstract
Multiobject spectroscopic observations of blue supergiants in NGC 3621, a spiral galaxy at a distance of 6.7 Mpc, carried out with the ESO Very Large Telescope and focal reducer/spectrograph are presented. We demonstrate the feasibility of quantitative stellar spectroscopy at distances approaching a tenfold increase over previous investigations by determining the chemical composition, stellar parameters, reddening, extinction, and wind properties of one of our targets, a supergiant of spectral type A1 Ia located on the outskirts of NGC 3621. The metallicity (determined from iron group elements) is reduced by a factor of 2 relative to the Sun, in qualitative agreement with the results from previous abundance studies based on H II region oxygen emission lines. Reddening and extinction are E(B-V) = 0.12 and AV = 0.37, respectively, mostly caused by the Galactic foreground. Comparing stellar wind momentum and absolute V magnitude with Galactic and M31 counterparts, we confirm the potential of the wind momentum-luminosity relationship as an alternative tool for estimating extragalactic distances.
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