The Accelerating Pace of Star Formation
  We study the temporal and spatial distribution of star formation rates in
four well-studied star-forming regions in local molecular clouds(MCs): Taurus,
Perseus, $\rho$ Ophiuchi, and Orion A. Using published mass and age estimates
for young stellar objects in each system, we show that the rate of star
formation over the last 10 Myrs has been accelerating and is (roughly)
consistent with a $t^2$ power law. This is in line with previous studies of the
star formation history of molecular clouds and with recent theoretical studies.
We further study the clustering of star formation in the Orion Nebula
Cluster(ONC). We examine the distribution of young stellar objects as a
function of their age by computing an effective half-light radius for these
young stars subdivided into age bins. We show that the distribution of young
stellar objects is broadly consistent with the star formation being entirely
localized within the central region. We also find a slow radial expansion of
the newly formed stars at a velocity of $v=0.17\,{\rm km\,s}^{-1}$, which is
roughly the sound speed of the cold molecular gas. This strongly suggests the
dense structures that form stars persist much longer than the local dynamical
time. We argue that this structure is quasi-static in nature and is likely the
result of the density profile approaching an attractor solution as suggested by
recent analytic and numerical analysis.
