Evidence of Hubble flow-like motion of young stellar populations away
  from the Perseus arm
  In this letter we present evidence of coherent outward motion of a sample of
young stars ($t<$30 Myr) in the Perseus Arm, whose apparent origin is located
in the vicinity of the W3/W4/W5 complex. Using astrometric and photometric data
from the Gaia DR2 catalog of an 8$^\circ$ radius field centered near W4, we
selected a sample of young, intermediate to high-mass star candidates. The
sample is limited to sources with parallax uncertainties below 20% and Bayesian
distance estimates within 1800 and 3100 pc. The selection includes embedded
stellar populations as well as young open clusters. Projected velocities
derived from perspective-corrected proper motions clearly suggest that the
young star population emerge from the Perseus arm, with a possible convergence
zone near W3/W4/W5 region, tracing a front that expands away at a rate of about
$15~{\rm km~s}^{-1}~{\rm kpc}^{-1}$.
