Annu. Rev. Astron. Astrophys. 1997. 35: 389-443 Copyright © 1997 by Annual Reviews. All rights reserved

3.3. Other Probes of Luminosity Evolution

One of the most satisfactory developments in galaxy evolution has been the verification of the redshift survey trends from completely independent approaches and, in particular, from the study of QSO absorbers. A redshift survey of 55 galaxies with 0.3 < z < 1 producing Mg II absorption in the spectra of background QSOs indicates little change in the volume density, characteristic luminosity, or rest-frame colors of typical L^* galaxies with established metallic halos Steidel et al 1994. Of importance, there appears a marked distinction between these systems and the rapidly evolving later-type galaxies that do not seem capable of producing significant Mg II absorption (Steidel et al 1993, 1996a). Although the straightforward physical interpretation has been questioned by Charlton & Churchill (1996) because of a poor correlation between the galaxy-QSO impact parameter and the Mg II absorption structure (Churchill et al 1996), and the paucity of nonabsorbing galaxies found at small impact parameters, these problems may relate to the difficulty of extrapolating from kinematics on small scales to the large scale properties of the absorbing galaxies.

Progress has also been made in studying possible evolution in the surface photometry and dynamics of various classes of distant galaxies. The crucial point in these studies is that evolution is normally inferred via a comparison with local data. Consequently it is important to understand exactly how the distant samples are selected. On the basis of luminosities and scale lengths for a magnitude-limited sample of galaxies selected to have faint bulge components drawn largely from the CFRS, Schade et al (1996) claimed a mean rest-frame B-disk brightening of 1 mag, compared to Freeman (1970) law by z = 0.55. Although this seems difficult to reconcile with LF studies from the same survey (Figure 6a and b), it should be noted the LF trends are -dependent, whereas the surface brightness test is not. Moreover, Schade et al applied their test globally to all systems with weak bulges, and presumably this incorporated the rapidly evolving lower luminosity systems discussed in Section 3.2.

Vogt et al (1996) obtained spatially resolved rotation curves for nine galaxies imaged with HST and, using the Tully-Fisher relation, obtained more modest changes of 0.6 mag to z 1 but warn of possible biases toward more luminous, larger star-forming galaxies at high z. Rix et al (1997), Simard & Pritchet (1997) sought to address the question of whether a faint blue galaxy is rotationally supported and thus selected the bluest or strongest emission line sources at z = 0.25-0.45, considered to be typical of the excess population. Rix et al measured line widths indicative of rotational support and, as with Simard & Pritchet, claimed to demonstrate that their galaxies are at least 1.5-mag brighter than expected from the local Tully-Fisher relation. The difficulty is finding an appropriate local calibration for these galaxies. Rix et al presented various alternatives, but more work is needed to define a self-consistent dynamic data set over a range in redshift in conjunction with HST images.