On the Survival of High-Altitude Open Clusters within the Milky Way
  Galaxy Tides
  It is a common assumption that high-altitude open clusters live longer
compared with clusters moving close to the Galactic plane. This is because at
high altitudes, open clusters are far from the disruptive effects of in-plane
substructures, such as spiral arms, molecular clouds and the bar. However, an
important aspect to consider in this scenario is that orbits of high-altitude
open clusters will eventually cross the Galactic plane, where the vertical
tidal field of the disk is strong. In this work we simulate the interaction of
open clusters with the tidal field of a detailed Milky Way Galactic model at
different average altitudes and galactocentric radii. We find that the life
expectancy of clusters decreases as the maximum orbital altitude increases and
reaches a minimum at altitudes of approximately 600 pc. Clusters near the
Galactic plane live longer because they do not experience strong vertical tidal
shocks from the Galactic disk; then, for orbital altitudes higher than 600 pc,
clusters start again to live longer due to the decrease in the number of
encounters with the disk. With our study, we find that the compressive nature
of the tides in the arms region and the bar have an important role on the
survival of small clusters by protecting them from disruption: clusters inside
the arms can live up to twice as long as those outside the arms at similar
galactocentric distance.
