Microlensing Predictions: Impact of Galactic Disc Dynamical Models
  Galactic model plays an important role in the microlensing field, not only
for analyses of individual events but also for statistics of the ensemble of
events. However, the Galactic models used in the field varies, and some are
unrealistically simplified. Here we tested three Galactic disc dynamic models,
the first is a simple standard model that was widely used in this field,
whereas the other two consider the radial dependence of the velocity
dispersion, and in the last model, the asymmetric drift. We found that for a
typical lens mass $M_{\rm L}=0.5M_{\odot}$, the two new dynamical models
predict $\sim16\%$ or $\sim5\%$ less long-timescale events (e.g., microlensing
timescale $t_{\rm E}>300$ days) and $\sim 5\%$ and $\sim 3.5\%$ more
short-timescale events ($t_{\rm E}<3$ days) than the standard model. Moreover,
the microlensing event rate as a function of Einstein radius $\theta_{\rm E}$
or microlensing parallax $\pi_{\rm E}$ also shows some model dependence (a few
percent). The two new models also have an impact on the total microlensing
event rate. This result will also to some degree affect the Bayesian analysis
of individual events, but overall, the impact is small. However, we still
recommend that modelers should be more careful when choosing the Galactic
model, especially in statistical works involving Bayesian analyses of a large
number of events. Additionally, we find the asymptotic power-law behaviors in
both $\theta_{\rm E}$ and $\pi_{\rm E}$ distributions, and we provide a simple
model to understand them.
