  The chemical composition of high redshift galaxies is an important property
which gives clues to their past history and future evolution and yet is
difficult to measure with current techniques. In this paper we investigate new
metallicity indicators, based upon the strengths of stellar photospheric
features at rest-frame ultraviolet wavelengths. By combining the evolutionary
spectral synthesis code Starburst99 with the output from the non-LTE model
atmosphere code WM-basic, we have developed a code that can model the
integrated ultraviolet stellar spectra of star-forming regions at metallicities
between 1/20 and twice solar. We use our models to explore a number of spectral
regions that are sensitive to metallicity and clean of other spectral features.
The most promising metallicity indicator is an absorption feature between 1935
A and 2020 A, which arises from the blending of numerous Fe III transitions. We
compare our model spectra to observations of two well studied high redshift
star-forming galaxies, MS1512-cB58 (a Lyman break galaxy at z = 2.7276), and
Q1307-BM1163 (a UV-bright galaxy at z = 1.411). The profiles of the
photospheric absorption features observed in these galaxies are well reproduced
by the models. In addition, the metallicities inferred from their equivalent
widths are in good agreement with previous determinations based on interstellar
absorption and nebular emission lines. Our new technique appears to be a
promising alternative, or complement, to established methods which have only a
limited applicability at high redshifts.
