Field Brown Dwarfs
Brown dwarfs are objects with masses lying between those of stars and
planets which lack the internal temperature to fuse Hydrogen. Hence
they fade and cool with time. I use proper motion (stars' motions
across the sky over several years) surveys based on datasets such as
surveys and numerical simulations to estimate the mass function and birthrate of these objects, giving clues to how these objects formed.
Young Stellar Clusters
Most stars and brown dwarfs are born in clusters. Members of such clusters can be selected from their common motion through space. Since objects in clusters are of a known age, their masses can easily be estimated from evolutionary models and a cluster mass function produced. The mass functions can then be compared to star formation models or to other cluster mass functions to look for variation between clusters due to formation environment.
Cool White Dwarfs
White dwarfs provide a fossil record of some of the earliest stars in
our Galaxy. These can be efficiently discovered using multiple epoch
surveys such as the Pan-STARRS 3PI survey. They provide a fossil record of
the Milky Way and allow us to date the formation of its various components.