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SUMMARY:Illuminating the Dark Universe with quasar-induced Ly-alpha emissi
 on - Sebastiano Cantalupo (UC Santa Cruz)
DTSTART:20130215T100000Z
DTEND:20130215T110000Z
UID:TALK41453@talks.cam.ac.uk
CONTACT:Martin Haehnelt
DESCRIPTION:Galaxy formation occurs along the densest part of the filament
 ary\nIntergalactic Medium where the gas can collapse and form stars. The\n
 proto-galactic phases preceding substantial star-formation are however\nun
 observable - in emission - in most of the studies conducted so far\nand th
 us poorly constrained. Recent theoretical models have suggested\nthat gas-
 rich\, low-mass haloes at high redshift may have indeed very\nlow or absen
 t star formation\, as a consequence of lower gas\nmetallicity\, H2 self-re
 gulation effects or reduced cooling accretion\ndue photoionization. These 
 "dark" galaxies may represent an important\ngas baryonic reservoir for lat
 er star-formation in more massive\nsystems and a crucial ingredient in ord
 er to reproduce the properties\nof current galaxy population. In this talk
 \, I will present the result\nof a an ongoing\, successful program that us
 es a new approach to\ndirectly detect and study these "dark" phases of gal
 axy formation: the\nkey idea is to use an external ``source of illuminatio
 n''\, a bright\nquasar\, to light up with fluorescent Ly-alpha emission da
 rk\, proto-\ngalactic clouds and dense streams around galaxies in a large\
 ncosmological volume. In the first part of the talk\, I will discuss our\n
 pilot project based on deep narrow-band imaging on VLT/FORS centered\non a
  z=2.4 hyper-luminous quasar: how we identified and characterized\nthe phy
 sical properties of the first sample of high-redshift\, "dark"\ngalaxy can
 didates. In the second part of the talk\, I will present the\ndetection of
  fluorescent emission from the Circumgalactic Medium of\nstar forming gala
 xies and very recent\, spectacular results obtained\nwith Keck/LRIS of the
  detection of hundred-kpc scale filaments\nsurrounding bright quasars.\n
LOCATION:Kavli LMR\, IoA
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