Physics Colloquium : "REIONIZING THE UNIVERSE: A BRIEF HISTORY OF BARYONS AND THE COSMIC WEB"
Professor Piero Madau, The department of Astronomy and Astrophysics University of California, Santa Cruz
The beaded filamentary network of intergalactic gas in which galaxies
form and evolve, and which gives origin to a “forest” of hydrogen
Lyman-alpha absorption lines in the spectra of distant quasars, encodes
information on the physics of structure formation, the nature of the dark
matter, the temperature and ionization state of baryons in the Universe.
The potential of the Lyman-alpha forest for constraining with percent
accuracy the matter density distribution on medium to small cosmological
scales has motivated the construction of the Dark Energy Spectroscopic
Instrument (DESI), which is measuring absorption line spectra backlit
by nearly a million high-redshift (z >2) quasars. In this talk I will
describe the multiple steps needed to connect flux fluctuations in quasar
spectra to physical parameters, present an unprecedented suite of thousands
of high-resolution hydrodynamical simulations of structure formation with
different thermal histories, and use it to perform a statistical comparison
of mock spectra with the observed 1D flux power spectrum and other data.
A likelihood analysis shows that, over the last 13 billion years, gas in the
cosmic web experienced four main heating and cooling epochs.
Event Organizer: Dr. Michael Geller