Ej. Barton et al., The Tully-Fisher relation as a measure of luminosity evolution: A low-redshift baseline for evolving galaxies, ASTRONOM J, 121(2), 2001, pp. 625-648
We use optical rotation curves to investigate the R-band Tully-Fisher prope
rties of a sample of 90 spiral galaxies in close pairs, covering a range of
luminosities, morphological types, and degrees of tidal distortion. The ga
laxies follow the Tully-Fisher relation remarkably well, with the exception
of eight distinct similar to3 sigma outliers. Although most of the outlier
s show signs of recent star formation, gasdynamical effects are probably th
e dominant cause of their anomalous Tully-Fisher properties. Four outliers
with small emission-line widths have very centrally concentrated line emiss
ion and truncated rotation curves; the central emission indicates recent ga
s infall after a close galaxy-galaxy pass. These four galaxies may be local
counterparts to compact, blue galaxies at intermediate redshift. The remai
ning galaxies have a negligible offset from the reference Tully-Fisher rela
tion, but a shallower slope (2.6 sigma significance) and a 25% larger scatt
er. We argue that triggered star formation is a significant contributor to
the slope difference. We characterize the nonoutlier sample with measures o
f distortion and star formation to search for third-parameter dependence in
the residuals of the TF relation. Severe kinematic distortion is the only
significant predictor of TF residuals; this distortion is not, however, res
ponsible for the slope difference from the reference distribution. Because
the outliers are easily removed by sigma clipping, we conclude that even in
the presence of some tidal distortion, detection of moderate (greater than
or similar to0.5 mag in rest-frame R) luminosity evolution should be possi
ble with high-redshift samples the size of this 90-galaxy study. The slope
of the TF relation, although difficult to measure, is as fundamental for qu
antifying luminosity evolution as the zero-point offset.