A Break in Spiral Galaxy Scaling Relations at the Upper Limit of Galaxy
  Mass
  Super spirals are the most massive star-forming disk galaxies in the universe
(Ogle et al. 2016, 2019). We measured rotation curves for 23 massive spirals
and find a wide range of fast rotation speeds (240-570 km/s), indicating
enclosed dynamical masses of 0.6 - 4E12 Msun. Super spirals with mass in stars
log Mstars / Msun > 11.5 break from the baryonic Tully-Fisher relation (BTFR)
established for lower mass galaxies. The BTFR power-law index breaks from 3.75
+/- 0.11 to 0.25 +/- 0.41 above a rotation speed of 340 km/s. Super spirals
also have very high specific angular momenta that break from the Fall (1983)
relation. These results indicate that super spirals are under-massive for their
dark matter halos, limited to a mass in stars of log Mstars / Msun < 11.8. Most
giant elliptical galaxies also obey this fundamental limit, which corresponds
to a critical dark halo mass of log Mhalo / Msun = 12.7. Once a halo reaches
this mass, its gas can no longer cool and collapse in a dynamical time. Super
spirals survive today in halos as massive as log Mhalo / Msun = 13.6,
continuing to form stars from the cold baryons they captured before their halos
reached critical mass. The observed high-mass break in the BTFR is inconsistent
with the Modified Newtonian Dynamics (MOND) theory (Bekenstein and Milgrom
1984).
