TITLE:

The Tully-Fisher Relation at Intermediate Redshifts

AUTHOR: Matthew A. Bershady

PUBLISHED: in the proceedings of ``Galaxies in the Young
Universe,'' Springer series ``Lecture Notes in Physics'',
eds. H. Hippelein, K. Meisenheimer, H.-J. Roser, 1996, p. 139

ABSTRACT:

Motivated by recent pioneering measurements of galaxy
kinematics at intermediate redshifts, we have begun a pilot
survey to measure rotation curves for blue, star-forming
galaxies between 0.05<z<0.35. The scientific impetus for such
measurements is to construct internal velocity - luminosity
relations at redshifts substantial enough to make cosmological
and evolutionary tests. Departures from a fiducial relation as
a function of redshift are sensitive to both space-time
curvature and the evolution of the mass-to-light ratio in
galaxies. Because of this ambiguity -- curvature vs. evolution
-- kinematics should be viewed as a new cosmological tool at
intermediate redshifts to be combined with additional
measurements. In particular, the apparent internal velocities,
colors, surface-brightness, and image shape are all unaffected
by curvature, so that this ensemble of observables can be used
unambiguously to explore galaxy evolution.

Here we discuss a well-defined method of target selection which
assures efficient measurement of spatially and spectrally
resolved kinematics, namely rotation curves. Spatial resolution
is critical since it is difficult to use integrated line-widths
to distinguish between, for example, a low-mass star-forming
galaxy and a high-mass galaxy with a central star-burst. For 18
of 19 appropriately selected galaxies to B<20.5 from Bershady
et al. (1994), we have successfully measured rotation curves
using the KAST spectrograph on the Lick 3m telescope with 1-2
hour integrations for each target. As a sanity check, we
present preliminary results for half of our sample: We measure
H0 to be ~75 km/s/Mpc at a median redshift of 0.15.