UC Berkeley

Despite models predicting the presence of millions of isolated black holes in the Milky Way galaxy, not a single one has been observed to date. Microlensing of background stars caused by these non-luminous black holes is theoretically the only observational method for detecting them. However black hole candidates obtained through photometric microlensing for astrometric follow-up have been scarce due to the limited number of surveys looking for microlensing events.

This thesis presents the first wide-field untargeted microlensing survey designed and executed on a multi-purpose synoptic instrument. The Zwicky Transient Facility (ZTF) has taken observations covering the visible Northern night sky in multiple filters every few nights for several years. This work makes predictions for the number of observable microlensing events contained within the ZTF surveys, implements significant improvements to ZTF long-wavelength optical calibration necessary to characterize these events, and carries out an all-sky search for microlensing events in the facility’s first several years of observations. A list of microlensing events containing black hole candidates is produced that cover regions of the Galactic plane and field stars not previously covered by microlensing campaigns.

ZTF is a predecessor to upcoming synoptic surveys such as the Vera C. Rubin Observatory and the Nancy Grace Roman Space Observatory. Challenges exist in processing the massive heterogeneous datasets these instruments will generate as they attempt to further many different scientific pursuits. The computational and statistical techniques developed within this thesis can help realize the ambitions to conduct microlensing surveys on these instruments.