Studying the Milky Way through its Lowest-Mass Members: The Roman Ultracool Dwarf Survey

Studying the Milky Way through its Lowest-Mass Members: The Roman Ultracool Dwarf Survey

Program ID	19101
Science Category	Stellar Physics
Program Type	Analysis
Category	Medium
Principal Investigator	Adam Burgasser
PI Institution	UC San Diego
Co-Investigators	()
Abstract	The lowest mass stars and brown dwarfs - the ultracool dwarfs - are a largely untapped population for studying the structure and evolution of the Milky Way due to their low luminosities. The Nancy Grace Roman Space Telescope's Community Surveys provide our first opportunity to use UCDs to study the Milky Way at large, while providing new empirical tests of low temperature atmospheres and substellar evolution. We propose to use Roman's High Latitude Time Domain Survey (HLTDS), High Latitude Wide Area Survey (HLWAS), and Parallel Fields to identify a large (millions), deep (out to 40 kpc), and robustly-characterized sample of ultracool dwarfs to achieve three primary science objectives: (1) measure the Milky Way’s thick disk and halo mass functions and star formation histories across the star/brown dwarf boundary for the first time, and evaluate the role of metallicity on low-mass star formation; (2) measure thin disk scaleheights of cool brown dwarfs to simultaneously constrain population ages and mass-dependent scattering in the Galactic potential; and (3) statistically measure wavelength-dependent variability associated with cloud structure with the largest synoptic sample of L/T transition dwarfs ever assembled. These scientific objectives will be achieved by creating a comprehensive empirical and theoretical template sample for Roman ultracool dwarf studies, developing robust machine learning models to select and characterize these sources in Roman photometry and spectroscopy, developing a low-mass population synthesis code that accounts for metallicity effects on atmospheres and evolution, and applying these resources to the first imaging and spectroscopic data from the HLWAS, HLTDS Deep, and Parallel fields. Our template resources, analysis tools, and discovery source catalogs will be made publicly available for science planning and investigations with other Community and General Astrophysics Surveys.