AN IMPROVED DISTANCE INDICATOR FOR SPIRAL GALAXIES THE 2-PARAMETER TULLY-FISHER RELATION IN URSA MAJOR

in the process of trying to understand the tullyfisher relation, the relation between luminosity and rotation velocity of spiral galaxies, we have found for the ursa major cluster that the scatter around the relation decreases substantially when we introduce a second parameter, the iras flux at 60 micron. this might be very important, since it leads to a better understanding of how to use the tullyfisher relation when determining galaxy distances. since distances from peculiar velocity measurements are very difficult to get, because the peculiar velocity of an individual galaxy is smaller than the uncertainty in the distance estimate, peculiar velocities might be subject to unknown systematic effects. therefore it is important to understand the way the tullyfisher relation works. the aim of the proposal is to expand this preliminary result for ursa major. the cluster population resembles that of field galaxies while the small velocity dispersion allows to discriminate foreground and background galaxies. its proximity enables us to obtain spatially resolved information for most of the individual galaxies. the ursa major cluster, which can be considered as a young cluster, is an excellent candidate to establish an improved tullyfisher relation. for this cluster we will increase the current irassample by a factor 2, and obtain much higher quality data. we have already obtained substantial datasets in the nearinfrared and in neutral hydrogen, and together with the iso data we will have a superior data set that will allow us to obtain a much better understanding of the tullyfisher relation than is currently available. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]