The Distance to M51
  Great investments of observing time have been dedicated to the study of
nearby spiral galaxies with diverse goals ranging from understanding the star
formation process to characterizing their dark matter distributions. Accurate
distances are fundamental to interpreting observations of these galaxies, yet
many of the best studied nearby galaxies have distances based on methods with
relatively large uncertainties. We have started a program to derive accurate
distances to these galaxies. Here we measure the distance to M51 - the
Whirlpool galaxy - from newly obtained Hubble Space Telescope optical imaging
using the tip of the red giant branch method. We measure the distance modulus
to be 8.58+/-0.10 Mpc (statistical), corresponding to a distance modulus of
29.67+/-0.02 mag. Our distance is an improvement over previous results as we
use a well-calibrated, stable distance indicator, precision photometry in a
optimally selected field of view, and a Bayesian Maximum Likelihood technique
that reduces measurement uncertainties.
