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The Galaxy is found to be in disequilibrium based on recent findings of theNorth/South (N/S) asymmetry and the phase mixing signatures, such as a phasespiral (snail) structure in the vertical phase space ($z-V_{z}$). We show thatthe N/S asymmetry in a tracer population of dwarfs may be quantitativelymodeled with a simple phase snail model superimposed on a smooth equilibriumbackground. As the phase snail intersects with the $z$ axis, the number densityis enhanced, and the velocity dispersion ($\sigma_{z}$) is decreased relativeto the other side of the Galactic plane. Fitting only to the observedasymmetric N/S $\sigma_{z}$ profiles, we obtain reasonable parameters for thephase space snail and the potential utilized in modeling the background,despite the complex dependence of the model on the potential parameters and thesignificant selection effects of the data. Both the snail shape and the N/Snumber density difference given by our best-fit model are consistent withprevious observations. The equilibrium background implies a local dark matterdensity of $0.0151^{+0.0050}_{-0.0051}$ ${\rm M}_{\odot}\,{\rm pc}^{-3}$. Thevertical bulk motion of our model is similar to the observation, but with a$\sim$1.2 $\rm km\,s^{-1}$ shift. Our work demonstrates the strong correlationbetween the phase space snail and the N/S asymmetry. Future observationalconstraints will facilitate more comprehensive snail models to unravel theMilky Way potential and the perturbation history encoded in the snail feature.

The North/South Asymmetry of the Galaxy: Possible Connection to the Vertical Phase Space Snail