Measuring galaxy distances from optical rotation curves

Abstract

We describe a distance indicator for spiral galaxies using detailed rotation curves derived from Ha velocity fields and I band CCD photometry. Two-dimensional velocity fields are obtained with an imaging Fabry-Perot spectrometer, with a velocity accuracy of better than 10 km/s. Rotation curves, based upon rotating disks geometries, are fit to these velocity fields. We present the I band photometry profiles, and the individual rotation curves for 75 galaxies. The extracted circular velocity is combined with I band magnitudes to form a Tully-Fisher relation, with a scatter of ∼ 0m.25-0m.3 mag. We discuss in some detail the accuracy of our photometric measures, the merits of the detailed rotati..