Uncertainties in galaxy rotation curves

Assessing the likelihood that rotation curve of a galaxy matches predictions from formation simulations requires uncertainties in circular speed as function radius derived observational data be statistically robust. Few presented literature meet this requirement. In paper we present new standalone tool, makemap, estimates fitted velocity at each pixel Gauss-Hermite fits to 3D spectral cube, together with its uncertainty obtained modified bootstrap procedure. We apply tool neutral hydrogen spectra for 18 galaxies THINGS sample, and maps uncertainties. propagate estimated map into our previously-described model fitting DiskFit derive curves. The obtain these take account not only errors, but also systemic velocity, position centre, inclination line sight, forced non-circular motion. They are therefore much better-defined than values have previously been available. Our on speeds differ previous by factors ranging up five, being smaller some cases larger others. conclude kinematic models well-resolved HI datasets vary widely their precision reliability, potentially value comparisons cosmological simulations.