case western reserve university



Probing inflation, dark matter, dark energy, etc. using the Lyman-alpha forest

Patrick McDonald (CITA)

Cosmologists work to answer some of the oldest questions of humanity: How did the Universe begin? What is it made of? What rules does it follow? Observations of the large-scale structure (LSS) of the Universe address these questions in several ways: Measurements of the scale dependence of density fluctuations tell us about the initial conditions for structure formation, set in the very early Universe. Measurements of the expansion and growth of structure with time tell us about the matter content and gravitational laws. I will mostly discuss one LSS probe: the Lyman-alpha forest (LyaF) - the absorption in high redshift quasar spectra by neutral hydrogen in the intergalactic medium. The LyaF provides a good probe of the density field over the redshift range z~2-5 on scales down to tens of kiloparsecs. When combined with the CMB on larger scales, the LyaF observed in thousands of quasar spectra from the Sloan Digital Sky Survey (SDSS) currently provides the best constraints on the power spectrum of initial density perturbations, neutrino masses that affect structure formation, and warm dark matter. These constraints should improve significantly in the near future. I will also discuss the SDSS-III/BOSS survey, the next generation of SDSS-LSS, which will focus on probing dark energy using the standard ruler provided by the baryonic acoustic oscillation feature, detectable both in galaxy clustering at z~0-0.7 and Lyman-alpha forest absorption at z~2-3.