The Detection of M-L-T-Y Dwarfs Belonging to our Milky Way Disks and Stellar Halo with the Roman Space Telescope

How many low-mass stars are in the Milky Way? And where are these low-mass stars and free-floating planet-like objects in our Galaxy? One can use the High Latitude Survey with the Roman Space Telescope to search for Galactic dwarf stars (M, L, T, and Y) to accurately model the 3D structure of the Milky Way disk in these low-mass (sub)stellar objects. Recent studies of Milky Way interlopers in high-redshift observations have revealed a 150-300 pc thick disk of these cool stars with 7% of the M-dwarfs in an oblate stellar halo.

Accurate typing has been shown to work on HST grism and photometric data using machine learning techniques. Such an approach can also be applied to Roman photometry producing accurate photometric typing to within two subtypes. The High Latitude Survey provides enough statistical power to model the Milky Way structural components (thin and thick disks and halo) for M-, L- and T/Y-dwarfs. This approach has the benefit to allow us to constrain scale-lengths, -heights and densities as well as the relative position of our Sun with respect to the disk of dwarf stars of our Milky Way. The total number of each brown dwarf type can then be inferred from each model, constraining the low-end of the Galaxy-wide Initial Mass Function (GIMF) for the first time and the fraction of stars in the halo, a prediction from cold dark matter structure formation.

Speaker: Benne Holwerda (University of Louisville)

The Roman Lecture Series is a monthly virtual lecture series focused on the scientific capabilities and technology of the Nancy Grace Roman Space Telescope, organized by Roman Mission partners.