Measuring cosmic expansion and growth with the Lyman-𝛼 forest in DESI

by Calum Gordon (IFAE)

Friday Sep 19, 2025, 11:00 AM → 1:00 PM Europe/Madrid

IFAE Seminar Room (In-Person)

This PhD thesis explores how the Lyman-α forest — a pattern of absorption lines in quasar spectra — can be used as a powerful tracer of the Universe’s large-scale structure. I present the first clustering measurements in the Lyman-α forest from Dark Energy Spectroscopic Instrument (DESI) data, and outline the analysis pipeline used to produce groundbreaking measurements of cosmic expansion. This work also develops new methods to correct for systematic effects, such as quasar redshift errors, improving the accuracy of precise cosmological inferences from the full shape of Lyman-α correlation functions. Finally, the thesis contains forecasts for the next-generation DESI-II survey, highlighting its potential to map the cosmos with unprecedented detail through quasars and high-redshift galaxies.

Supervisor: Andreu Font Ribera
Committee members: Keir Rogers, Natalia Porqueres, Jordi Miralda Escudé