Gravitational Microlensing Event Statistics for the Zwicky Transient
  Facility
  Microlensing surveys have discovered thousands of events with almost all
events discovered within the Galactic bulge or toward the Magellanic clouds.
The Zwicky Transient Facility (ZTF), while not designed to be a microlensing
campaign, is an optical time-domain survey that observes the entire northern
sky every few nights including the Galactic plane. ZTF observes $\sim10^9$
stars in g-band and r-band and can significantly contribute to the observed
microlensing population. We predict that ZTF will observe $\sim$1100
microlensing events in three years of observing within $10^\circ$ degrees
latitude of the Galactic plane, with $\sim$500 events in the outer Galaxy
($\ell \geq 10^\circ$). This yield increases to $\sim$1400 ($\sim$800) events
by combining every three ZTF exposures, $\sim$1800 ($\sim$900) events if ZTF
observes for a total of five years, and $\sim$2400 ($\sim$1300) events for a
five year survey with post-processing image stacking. Using the microlensing
modeling software PopSyCLE, we compare the microlensing populations in the
Galactic bulge and the outer Galaxy. We also present an analysis of the
microlensing event ZTF18abhxjmj to demonstrate how to leverage these population
statistics in event modeling. ZTF will constrain Galactic structure, stellar
populations, and primordial black holes through photometric microlensing.
