Galactic archaeology
Stellar streams
Tidally disrupted star clusters and dwarf galaxies stretch into streams that record the Milky Way's gravitational field and accretion history. I founded and lead the Southern Stellar Stream Spectroscopic Survey (S5), mapping the 6D phase space and chemistry of streams across the southern sky.
On-sky map of a dozen S5 streams. Li et al. 2022
Near-field cosmology
Dwarf galaxies & dark matter
The faintest satellite galaxies are the most dark-matter-dominated systems known. Their internal kinematics and chemistry constrain both galaxy formation on the smallest scales and the particle nature of dark matter.
Members & velocities of the distant dwarf Eridanus II. Li et al. 2017
Survey science
Imaging & spectroscopic surveys
As a builder of both the Dark Energy Survey (DES) and the Dark Energy Spectroscopic Instrument (DESI), and former chair of the DESI Milky Way Survey and DES Milky Way working groups, I help turn surveys of millions of stars into chemo-dynamical maps of the Galactic halo — with LSST and future facilities on the horizon.
Example S5 spectra and derived parameters. Li et al. 2019
Instrumentation
Spectrographs & detectors
I build the instruments that make these surveys possible — from DESI's focus-and-alignment system to DMD-MOS, a student-driven multi-object spectrograph prototype now commissioned on sky, novel detectors, and a Canadian contribution to the ANDES instrument for the ELT.
The DMD-MOS prototype on the UofT campus. DMD-MOS project page