ASTRONOMY COLLOQUIUM

The Lyman-alpha (Lya) forest is currently one of the most powerful probes of large-scale structure at high redshift (2 < z < 4). This is made possible by large spectroscopic surveys that measure hundreds of thousands of quasar spectra. Over the last decade, the Lya forest has been successfully used to measure the high redshift expansion rate, and place tight constraints on the nature of dark energy. The next generation of cosmological surveys is spearheaded by the Dark Energy Spectroscopic Instrument (DESI), which has finished collecting its first year of data in June 2022. This already comprises the largest ever spectroscopic data set. In this talk, I will show how DESI is using the Lya forest to comprehensively map the cosmic expansion history between redshifts 2 and 4, and present the current status of our analysis of Year 1 data. I will also discuss my recent work on how we can take full advantage of the cosmological information contained in the 3D distribution of the Lya forest, and the exciting opportunities this can unlock.