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Session 103 - Galaxy Evolution.
Display session, Thursday, January 16
Optical rotation curves are presented for eight faint field galaxies in the region of the Hubble Deep Field (HDF) in the redshift range 0.15 \lesssim z \lesssim 0.75, based on moderate--resolution spectroscopy and V photometry obtained with the Keck 10 m telescope. These data were augmented with high--resolution F814W Hubble Space Telescope images from WFPC2, which provided I photometry and galaxy morphologies, orientations, and inclinations. Terminal disk velocities were derived from the spatially resolved velocity profiles by modeling the effects of seeing, finite slit width, slit alignment along the galaxy major axis, and inclination for each source. These data extend the earlier sample of Vogt etal (1996) to significantly fainter luminosities (M_B \sim -19, for q_0 = 0.05, Hubble constant = 75). The terminal velocities and absolute magnitudesare compared to local galaxies via the Tully--Fisher relation. The extended sample strengthens our previous result that the kinematics of these distant galaxies provide evidence for only a modest increase in luminosity (\DeltaM_B \lesssim 0.4). We see no deviation from a linear TF relation for intrnsically fainter galaxies. The disk surface brightnesses are also compared to those of local disk galaxies, and the results are consistent with the TF determination in that the evolution measured is \sim 0.5 mag.
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