Cosmology at cosmic noon and beyond

Most galaxy surveys map the relatively nearby Universe. Lyman-Break Galaxies (LBGs) let us push much further — to redshifts $2 < z < 5$, when the Universe was only one-to-three billion years old and forming stars most vigorously. Mapping structure this far back is one of the most promising ways to sharpen constraints on dark energy and the growth of structure.

I co-lead the Lyman-Break Galaxies topical team within the Dark Energy Science Collaboration (DESC), where we are developing the tools to turn future LBG samples — from surveys like the Vera C. Rubin Observatory’s LSST — into precision cosmological probes.

Getting the systematics right

LBGs are selected by the tell-tale “break” in their spectra, where light blueward of the Lyman limit is absorbed. But that absorption happens in the intergalactic medium (IGM), and the models we use for it are imperfect.

My current work quantifies how mis-specifying the IGM attenuation model biases the cosmological parameters inferred from LBGs — a prerequisite for trustworthy high-redshift cosmology, and for realizing the statistical power of the next generation of surveys.