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We present dynamical distance estimates for 15 Galactic globular clusters anduse these to check the consistency of dynamical and photometric distanceestimates. For most of the clusters, this is the first dynamical distanceestimate ever determined. We extract proper-motion dispersion profiles usingcleaned samples of bright stars from the Hubble Space Telescope proper-motioncatalogs recently presented in Bellini et al. (2014) and compile a set ofline-of-sight velocity-dispersion profiles from a variety of literaturesources. Distances are then estimated by fitting spherical, non-rotating,isotropic, constant mass-to-light (M/L) dynamical models to the proper-motionand line-of-sight dispersion profiles together. We compare our dynamicaldistance estimates with literature photometric estimates from the Harris (1996,2010 edition) globular cluster catalog and find that the mean fractionaldifference between the two types is consistent with zero at just $-1.9 \pm 1.7\%$. This indicates that there are no significant biases in either estimationmethod and provides an important validation of the stellar-evolution theorythat underlies photometric distance estimates. The analysis also estimatesdynamical M/L ratios for our clusters; on average, the dynamically-inferred M/Lratios agree with existing stellar-population-based M/L ratios that assume aChabrier initial mass function (IMF) to within $-8.8 \pm 6.4 \%$, implying thatsuch an IMF is consistent with our data. Our results are also consistent with aKroupa IMF, but strongly rule out a Salpeter IMF. We detect no correlationbetween our M/L offsets from literature values and our distance offsets fromliterature values, strongly indicating that our methods are reliable and ourresults are robust.

Hubble Space Telescope proper motion (HSTPROMO) catalogs of Galactic globular clusters. III. Dynamical distances and mass-to-light ratios