Moderate-resolution spectroscopic observations from the Keck 10m telescope
are used to derive internal kinematics for eight faint disk galaxies in the
fields flanking the Hubble Deep Field. The spectroscopic data are combined with
high-resolution F814W WFPC2 images from the Hubble Space Telescope which
provide morphologies and scale-lengths, inclinations and orientations. The
eight galaxies have redshifts 0.15 < z < 0.75, magnitudes 18.6 < I_814 < 22.1
and luminosities -21.8 < M_B < -19.0 (H_0 = 75 and q_0 = 0.05). Terminal disk
velocities are derived from the spatially-resolved velocity profiles by
modeling the effects of seeing, slit width, slit misalignment with galaxy major
axis, and inclination for each source. These data are combined with the sample
of Vogt et al. (1996) to provide a high-redshift Tully-Fisher relation that
spans three magnitudes. This sample was selected primarily by morphology and
magnitude, rather than color or spectral features. We find no obvious change in
the shape or slope of the relation with respect to the local Tully-Fisher
relation. The small offset of < 0.4 B mag with respect to the local relation is
presumably caused by luminosity evolution in the field galaxy population, and
does not correlate with galaxy mass. A comparison of disk surface brightness
between local and high-redshift samples yields a similar offset, ~0.6 mag.
These results provide further evidence for only a modest increase in luminosity
with lookback time.Comment: Text is 9 pages (13 with figures, images in JPG format here for
brevity). Full text and postscript figures are available at
http://www.ucolick.org/~nicole/pubs/pubs.html#vfp2 and
http://tarkus.pha.jhu.edu/deep/publications.html . Accepted for publication
by The Astrophysical Journal Letter