In order to use most effectively the Tully-Fisher relation as a
distance indicator, we need to understand better the general properties
of disk galaxies. Over the years, we have accumulated a large archive
of multiwavelength imaging and spectroscopic data and we are currently
using the entire set to probe the nature of spiral galaxies and to
look for additional parameters that might affect the use of the TF relation
for distance measures.
- Karen Masters used the 2MASS database to explore the effects of
internal extinction in galaxies via statistical tests. She explored a
simple photometric model for extinction which is able to qualitatively
reproduce the observed trends and also revisited the issue of
the variation in the amount of extinction with galaxy luminosity.
- Barbara Catinella has used a homogenous sample of some 2000 spiral
galaxies to construct average, or template,
rotation curves in separate luminosity classes, spanning 6 magnitudes
in I-band luminosity. These template rotation curves
show no evidence of velocity decline within the spatial
scales over which they are sampled, even in the case of the most luminous
systems. In contrast to some previous expectations, the fastest rotators
(most luminous galaxies) have, on average, rotation curves that are flat
or mildly rising beyond the optical radius, implying that the dark
matter halo makes an important contribution to the kinematics
also in these systems.
The template rotation curves and the derived functional fits provide
quantitative constraints for studies of the structure and evolution of
disk galaxies, which aim at reproducing the internal kinematics
properties of disks at the present cosmological epoch.
- Karen Masters and Chris Springob have combined the EGG HI and optical
archival datasets to construct a new TF database, referred to as SFI++.
This work is to be submitted for publication soon!