An Updated SynthPop Model for Microlensing Simulations I: Model Description & Evaluation

TL;DR

This paper introduces an updated Galactic model within the SynthPop framework, optimized for simulating the Nancy Grace Roman Space Telescope's microlensing survey, and evaluates its accuracy against observational data.

Contribution

The authors present a new, tuned Galactic model that better replicates stellar populations and microlensing rates, addressing previous modeling shortcomings for the Roman Space Telescope.

Findings

Good agreement with stellar catalogs in much of the bulge

Over-predicts optical microlensing event rate by about 20%

Remaining inconsistencies near the Galactic plane

Abstract

The optimization and interpretation of microlensing surveys depends on having an accurate model of the Milky Way. However, existing population synthesis Galactic modeling tools often perform poorly in replicating the stellar contents of the inner Galactic bulge region and reproducing microlensing survey results. We present an updated Galactic model implementation within the \synthpop framework that has been tuned for simulating the upcoming {\it Nancy Grace Roman Space Telescope}'s Galactic Bulge Time Domain Survey (RGBTDS). We evaluate the model against stellar catalogs and kinematics from optical and infrared surveys toward the Galactic bulge, finding good agreement in much of the bulge, including the RGBTDS' contiguous lower bulge fields. However, within Galactic latitudes of $b\lesssim0.5^\circ$ of the Galactic plane, some inconsistencies arise which may impact projections for the RGBTDS' Galactic center field. The model over-predicts optical microlensing event rate per star measurements by a $\sim20$\%, but detailed comparisons to near-infrared measurements are hampered by their lack of detection efficiencies. {\it Roman}'s GBTDS and Galactic Plane Survey will be instrumental in resolving the remaining model inconsistencies and improving our understanding of the structure of the central few degrees of our Galaxy.