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The Zwicky Transient Facility is a time-domain optical survey that has substantially increased our ability to observe and construct massive catalogs of astronomical objects by use of its 47 square degree camera that can observe in multiple filters. However the telescope’s i-band filter suffers from significant atmospheric fringes that reduce photometric precision, especially for faint sources and in multi-epoch co-additions. Here we present a method for constructing models of these atmospheric fringes using Principal Component Analysis that can be used to identify and remove these artifacts from contaminated images. In addition, we present the Uniform Background Indicator as a quantitative measurement of the reduced correlated background noise and photometric error present after removing fringes. We conclude by evaluating the effect of our method on measuring faint sources through the injection and recovery of artificial stars in both single-image epochs and co-additions. Our method for constructing atmospheric fringe models and applying those models to produce cleaned images is available for public download in the open source Python package fringez (https://github.com/MichaelMedford/fringez).

© 2020. The American Astronomical Society. All rights reserved. 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, including the Galactic plane, every few nights. The ZTF observes ∼109 stars in the g and r bands and can significantly contribute to the observed microlensing population. We predict that the ZTF will observe ∼1100 microlensing events in 3 yr of observing within 10° latitude of the Galactic plane, with ∼500 events in the outer Galaxy (ℓ ≥ 10°). This yield increases to ∼1400 (∼800) events by combining every three ZTF exposures, ∼1800 (∼900) events if the ZTF observes for a total of 5 yr, and ∼2400 (∼1300) events for a 5 yr survey with postprocessing 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. The ZTF will constrain Galactic structure, stellar populations, and primordial black holes through photometric microlensing.

© 2020. The American Astronomical Society. All rights reserved. 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, including the Galactic plane, every few nights. The ZTF observes ∼109 stars in the g and r bands and can significantly contribute to the observed microlensing population. We predict that the ZTF will observe ∼1100 microlensing events in 3 yr of observing within 10° latitude of the Galactic plane, with ∼500 events in the outer Galaxy (ℓ ≥ 10°). This yield increases to ∼1400 (∼800) events by combining every three ZTF exposures, ∼1800 (∼900) events if the ZTF observes for a total of 5 yr, and ∼2400 (∼1300) events for a 5 yr survey with postprocessing 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. The ZTF will constrain Galactic structure, stellar populations, and primordial black holes through photometric microlensing.