OPTICAL-ROTATION CURVES OF DISTANT FIELD GALAXIES - SUB-L-ASTERISK SYSTEMS

Moderate-resolution spectroscopic observations from the Keck 10 m tele scope are used to derive internal kinematics for eight faint disk gala xies in the fields flanking the Hubble Deep Field. The spectroscopic d ata are combined with high-resolution F814W Wide Field Planetary Camer a 2 images from the Hubble Space Telescope that provide morphologies, scale lengths, inclinations, and orientations. The eight galaxies have redshifts 0.15 less than or similar to z less than or similar to 0.75 , magnitudes 18.6 less than or equal to I-814 less than or equal to 22 .1, and luminosities -21.8 less than or equal to M-B less than or equa l to -19.0 (H-0 = 75 km s(-1) Mpc(-1) and q(0) = 0.05). Terminal disk velocities are derived from the spatially resolved velocity profiles b y modeling the effects of seeing, slit width, slit misalignment with g alaxy major axis, and inclination for each source. These data are comb ined with the sample of Vogt et al. to provide a high-redshift Tully-F isher relation that spans 3 magnitudes. This sample was selected prima rily by morphology and magnitude, rather than color or spectral featur es. We find no obvious change in the shape or slope of the relation wi th respect to the local Tully-Fisher relation. The small offset of les s than or similar to 0.4 mag in B with respect to the local relation i s presumably caused by luminosity evolution in the field galaxy popula tion and does not correlate with galaxy mass. A comparison of disk sur face brightness between local and high-redshift samples yields a simil ar offset, similar to 0.6 mag. These results provide further evidence for only a modest increase in luminosity with look-back time.