Graduating student, Josh Speagle, awarded the annual Keto Prize for his thesis "Mapping the Milky Way in the Age of Gaia."

May 8, 2020
Josh Speagle

The Eric R. Keto Prize for Graduate Students in Theoretical Astrophysics, endowed with a generous donation by ITC Senior Member Eric Keto, is awarded each year for the best thesis in theoretical astrophysics by a student at the CfA, as selected by the Senior Members of the ITC.

In the Fall, Josh will begin a five year Dunlap Postdoctoral Fellowship (Dunlap Institute, University of Toronto)

Abstract of Josh's thesis


A central problem in astronomy is converting the 2-D positions of sources observed on the sky to their 3-D
positions in space. This has become especially important in the last decades as large-scale surveys such as Gaia are
providing astrometric and photometric measurements of billions of sources. These datasets open up an entirely
new regime for understanding galaxies such as our own Milky Way, provided we can develop the appropriate
statistical algorithms to analyze them and the computational methods necessary to apply them at unprecedented

In pursuit of these goals, I present new computational and statistical algorithms both for general use as well
as specifically to model the 3-D distribution of stars and dust using these large datasets. Using empirical stellar
models, I derive new constraints on the 3-D distribution of nearby star-forming regions. Using state-of-the-art
theoretical stellar models, I then derive the 3-D distribution of 170M stars at high Galactic latitudes along with
their associated stellar properties. I also discuss methods used to characterize systematics in both the photometric
data and the underlying stellar models.

These results are accompanied by publicly available datasets, interactive figures, and open-source code that can
be used by others to explore my results as well as further their own research interests.

Two relevant papers: dynestylocal ISM