  The Baryonic Tully-Fisher Relation (BTFR) is an empirical relation between
baryonic mass and rotation velocity in disk galaxies. It provides tests of
galaxy formation models in LCDM and of alternative theories like MOND.
Observations of gas rich galaxies provide a measure of the slope and
normalization of the BTFR that is more accurate (if less precise) than that
provided by star dominated spirals, as their masses are insensitive to the
details of stellar population modeling. Recent independent data for such
galaxies are consistent with Mb = AVf^4 with A = 47+/-6 Msun (km/s)^-4. This is
equivalent to MOND with $a_0 = 1.3 +/- 0.3 A/s/s. The scatter in the data is
consistent with being due entirely to observational uncertainties. It is
unclear why the physics of galaxy formation in LCDM happens to pick out the
relation predicted by MOND. We introduce a feedback efficacy parameter E to
relate halo properties to those of the galaxies they host. E correlates with
star formation rate and gas fraction in the sense that galaxies that have
experienced the least star formation have been most impacted by feedback.
