The universal acceleration scale from stellar feedback
  It has been established for decades that rotation curves deviate from the
Newtonian gravity expectation given baryons alone below a characteristic
acceleration scale $g_{\dagger}\sim 10^{-8}\,\rm{cm\,s^{-2}}$, a scale promoted
to a new fundamental constant in MOND. In recent years, theoretical and
observational studies have shown that the star formation efficiency (SFE) of
dense gas scales with surface density, SFE $\sim \Sigma/\Sigma_{\rm crit}$ with
$\Sigma_{\rm crit} \sim \langle\dot{p}/m_{\ast}\rangle/(\pi\,G)\sim
1000\,\rm{M_{\odot}\,pc^{-2}}$ (where $\langle \dot{p}/m_{\ast}\rangle$ is the
momentum flux output by stellar feedback per unit stellar mass in a young
stellar population). We argue that the SFE, more generally, should scale with
the local gravitational acceleration, i.e. that SFE $\sim g_{\rm
tot}g_\mathrm{crit} \equiv (G\,M_{\rm tot}/R^{2}) /
\langle\dot{p}/m_{\ast}\rangle$, where $M_{\rm tot}$ is the total gravitating
mass and $g_\mathrm{crit}=\langle\dot{p}/m_{\ast}\rangle = \pi\,G\,\Sigma_{\rm
crit} \approx 10^{-8}\,\rm{cm\,s^{-2}} \approx g_{\dagger}$. Hence the observed
$g_\dagger$ may correspond to the characteristic acceleration scale above which
stellar feedback cannot prevent efficient star formation, and baryons will
eventually come to dominate. We further show how this may give rise to the
observed acceleration scaling $g_{\rm obs}\sim(g_{\rm
baryon}\,g_{\dagger})^{1/2}$ (where $g_{\rm baryon}$ is the acceleration due to
baryons alone) and flat rotation curves. The derived characteristic
acceleration $g_{\dagger}$ can be expressed in terms of fundamental constants
(gravitational constant, proton mass, and Thomson cross section):
$g_{\dagger}\sim 0.1\,G\,m_{p}/\sigma_{\rm T}$.
