Sebastiano Cantalupo - September 25, 2015

Illuminating the Dark Universe with Quasar-induced Lyman-alpha Emission

Gravitational collapse during the Universe's first billion years transformed 
a nearly homogeneous matter distribution into a network of filaments 
- the Cosmic Web - where galaxies form and evolve and where the majority 
of baryons reside as rarefied gas.

Because most of this material is too diffuse to form stars, its 
study has been limited so far to absorption probes against background sources. 

In this talk, I will present the results of a new, successful program to 
directly detect and study cosmic gas in the early Universe.

This experiment uses external 'source of illuminations', bright quasars, 
to light up with fluorescent Lyman-alpha emission 'dark' proto-galactic clouds, 
dense streams around galaxies (the Circumgalactic Medium) and the Cosmic Web. 

In particular, I will show results from ultra-deep narrow-band imaging and 
recent integral-field-spectroscopy as a part of the MUSE GTO program that 
revealed numerous 'dark galaxies' and giant Lyman-alpha emitting filaments. 

Finally, I will discuss how the unexpectedly high luminosities of the giant 
Lyman-alpha Nebulae, together with other constraints from Helium and metal 
extended emission, present a serious challenge for our current understanding 
of the Intergalactic and Circumgalactic media based on hydrodynamical 
cosmological simulations.