Galaxies Hidden in the Forest as a new BAO tracer (and other applications)

The acceleration of the expansion rate of the Universe is yet to be explained. Several models, including LCDM, try to explain this acceleration. LCDM bases its explanation on a mysterious dark energy, adding up to ~75% of the total energy density of the Universe. Other models present modified theories of gravity to explain this effect. But which one is correct? The expansion history of the Universe is a great observable to discriminate between these models. I will talk about measurements of this expansion history at redshift greater than 2 using BAO with the Lyman alpha forest, and review the latest measurements. I will motivate how galaxies in absorption can be affecting our measurements and explain what do we need to extract them and use them as a new BAO tracers. I will end on a note on other possible applications of these galaxies including the creation of new IGM observables for simulations.