APEC Seminar (Astronomy - Particle Physics - Experimental Physics - Cosmology)

Speaker: Daniele Sorini (MPIA)
Title: Constraining Cosmology and Galaxy Formation with Lyman-alpha absorption
Date (JST): Wed, Dec 13, 2017, 11:00 - 12:00
Place: Seminar Room A
Abstract: Lyman-alpha (Ly-a) absorption features detected in quasar spectra in the redshift range 0<z<6 are a powerful tool to probe the intergalactic and circumgalactic media (IGM/CGM) and, consequently, to constrain models of galaxy formation and cosmology. In the first part of the talk, I will present a novel semi-analytic technique to predict various statistics of Ly-a absorption in the IGM with large N-body cosmological simulations, allowing us to overcome numerical challenges posed by cosmological hydrodynamic simulations, thus enabling accurate investigation of the Ly-a absorption on 〜Gpc scales. In the second part of the talk, I will compare predictions of state-of-the-art hydrodynamic cosmological simulations with observations of the mean Ly-a absorption around foreground galaxies, at different transverse distances (〜20kpc-20Mpc) from background quasars. Far from galaxies >2Mpc, the simulations asymptotically match the observations, because the LCDM model successfully describes the ambient IGM. This represents a critical advantage of studying the mean absorption profile.
However, significant differences between the simulations, and between simulations and observations are present on scales 20kpc-2Mpc, illustrating the challenges of accurately modeling and resolving galaxy formation physics. It is noteworthy that these differences are observed as far out as 〜2Mpc, indicating that the `sphere of influence' of galaxies could extend to approximately 〜20 times the halo virial radius (〜100kpc). Current and upcoming observations are very precise on these scales and can thus strongly discriminate between different galaxy formation models..