Predictions for the Detection and Characterization of Galactic Disk Microlensing Events by LSST

Abstract

Abstract The upcoming Large Synoptic Survey Telescope (LSST) survey will provide an unprecedented opportunity for studying populations of intrinsically faint objects using microlensing. The LSST’s large field of view and aperture allow effective time-series observations of many stars in the Galactic disk and bulge. Here, we combine Galactic models (for ) and simulations of LSST observations to study how observing strategies affect the number and properties of microlensing events detected by LSST. Generally, detectable microlensing events are (a little) longer than events observable with current surveys. In Galactic bulge fields, LSST should detect on the order of 600 microlensing events per square degree as compared to 19 in disk fields. Improving the cadence from 6 to 2 days approximately doubles the number of detectable microlensing events throughout the Galaxy. We develop an Operations Simulator (OpSim)–based simulation to predict the characteristics of detectable microlensing events in different OpSim strategies and compare them. Based on baseline_2018a, minion_1016, and colossus_2664 OpSim simulations, LSST will observe with either 900 or 170 epochs in different observing times and cadences. With worse cadences LSST will detect longer microlensing events of brighter stars with lower blending. Although increasing the observing time from 1 to 10 yr with a fixed number of epochs does not change the total number of microlensing events significantly, the longer observing time lets one discern artificial effects and measure baseline fluxes, parallax, etc. If LSST spends enough time observing near the Galactic plane, then the large number of microlensing events will allow studies of the Galactic distribution of planets and searches for isolated black holes among a wealth of other scientific cases.