Research

Reading the Milky Way's history in its stars

My group combines wide-field imaging and spectroscopic surveys with deep, targeted follow-up observations to map the Milky Way and its satellites — and to use them as cosmological probes of dark matter.

On-sky map of stellar streams observed by S5 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
Color-magnitude diagram and member velocities of the dwarf galaxy Eridanus II 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
Example stellar spectra from the S5 survey with derived stellar parameters 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
The DMD-MOS prototype spectrograph in front of the UofT sign on campus 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

Where the data comes from

Surveys & collaborations

My science is built on the world's major sky surveys, several of which I help lead.

S5 — founder & leader DESI — builder, former MWS WG chair DES — builder, former MW WG chair DELVE LSST / Rubin SDSS-V Euclid MSE ANDES / ELT

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Publications & talks

A full, up-to-date publication list lives on my publications page, with links to ADS and Google Scholar. For the full record of grants, service, and observing experience, see my CV.

Recorded talks:

New to the field? Good places for students to start: