Piero Madau, Department of Astronomy and Astrophysics, University of California Santa Cruz: The dark and luminous side of structure formation

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 will measure 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 hundreds 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.


The program QUID ULTRA? Frontiers and Controversies in Astrophysics is a series of monthly prestigious colloquia that will be
running from early February till December 2021. This initiative has been funded by Sapienza University with the co-sponsorship
of INAF/Astronomical Observatory of Rome and of the joint PhD program in Astronomy, Astrophysics and Space Science of Sapienza,
Tor Vergata University and INAF.

Due to the pandemic situation, the first 6 colloquia will be held online via zoom.
The scientific program and all the information on how to attend the meeting can be found on the project website: www.quidultra.it.

Looking forward to seeing you soon,

Raffaella Schneider (on behalf of the SOC)

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