A robust method for measuring the Hubble parameter

We obtain a robust, non-parametric, estimate of the Hubble constant from th e linear diameters and rotation velocities of galaxies in the recent KLUN s ample, calibrated using Cepheid distances to Hubble Space Telescope Key Pro ject galaxies. There are two key features that make our analysis considerab ly more robust than previous work. First, the method is independent of the spatial distribution of galaxies and is insensitive to Malmquist bias. It m ay, therefore, be applied to more distant samples than so-called 'plateau' methods - making it much less vulnerable to the impact of peculiar motions in the Local Supercluster. Secondly, we include information on the galaxy r otation velocities in a fully non-parametric manner: unlike the conventiona l Tully-Fisher relation we reconstruct a robust estimate of the cumulative distribution function of galaxy diameter at given rotation velocity, withou t requiring the assumption of, for example, a linear Tully-Fisher relation with symmetric Gaussian residuals. Using this robust method we find H-0 = 65 +/- 6 km s(-1) Mpc(-1) from our a nalysis - in excellent agreement with many recent determinations of the Hub ble parameter, although somewhat larger than previous results using galaxy diameters.