Testing Distance Estimators with the Fundamental Manifold
  We demonstrate how the Fundamental Manifold (FM) can be used to
cross-calibrate distance estimators even when those "standard candles" are not
found in the same galaxy. Such an approach greatly increases the number of
distance measurements that can be utilized to check for systematic distance
errors and the types of estimators that can be compared. Here we compare
distances obtained using SN Ia, Cepheids, surface brightness fluctuations, the
luminosity of the tip of the red giant branch, circumnuclear masers, eclipsing
binaries, RR Lyrae stars, and the planetary nebulae luminosity functions. We
find no significant discrepancies (differences are < 2 sigma) between distance
methods, although differences at the ~10% level cannot yet be ruled out. The
potential exists for significant refinement because the data used here are
heterogeneous B-band magnitudes that will soon be supplanted by homogeneous,
near-IR magnitudes. We illustrate the use of FM distances to 1) revisit the
question of the metallicity sensitivity of various estimators, confirming the
dependence of SN Ia distances on host galaxy metallicity, and 2) provide an
alternative calibration of H_0 that replaces the classical ladder approach in
the use of extragalactic distance estimators with one that utilizes data over a
wide range of distances simultaneously.
