Rolf Kudritzki
Institute for Astronomy, University of Hawaii at Manoa

"Dissecting Galaxies with the Brightest Stars in the Universe"

Stellar astronomy has reached the stage, where the the quantitative spectral
analysis of individual stars in distant galaxies can provide invaluable
information about galaxy evolution. The ideal objects for this purpose are B
and A supergiants, which are the intrinsically brightest "normal" stars at
visual light. With absolute visual magnitudes up to -9 they are as bright as
globular clusters or faint dwarf galaxies. They are ideal to study young
stellar populations in galaxies beyond the Local Group to determine their
chemical composition, evolution, interstellar extinction, reddening laws and
distances. The talk will summarize our knowledge of these objects based on high
spectral resolution studies in the Milky Way and Local Group. It will then
present most recent results on the quantitative spectral analysis of such
objects in galaxies beyond the Local Group based on medium and low resolution
spectra obtained with the ESO VLT and Keck. We will describe the analysis
method, discuss the determination of metallicity and metallicity gradients and
we will introduce a new method to measure accurate extragalactic distances
based on the stellar gravities and effective temperatures obtained. Finally, we
will discuss the perspectives of future work using the the giant ground-based
telescopes of the next generation such as the TMT and the E-ELT.