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9 November 2009
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Claude-André Faucher-Giguere (CfA)
'Ly-alpha Emission from Galaxy Formation'
Astronomers have exquisite observations of both galaxies (by directly
imaging their stars) and of the intergalactic medium (in absorption
spectra of background sources). While we know that the galactic baryons
must have been accreted from the IGM, we currently have virtually no
direct observations of the galaxy assembly process itself. Contrary to
the classical picture of galaxy formation in which the accreting gas is
shock-heated to the virial temperature of the halo before cooling,
recent simulations show that most of the gas is instead accreted in
cold streams, with temperatures T~10^4-10^5 K. At these temperatures,
the accretion streams will radiate primarily in the Ly-alpha line and
may be accessible to current observations. I will present new results
combining cosmological hydrodynamical simulations with Ly-alpha radiative
transfer, including the expected Ly-alpha luminosities, spectra, and
morphologies of the accretion streams. I will discuss whether these
streams may have already been detected in the form of extended 'Ly-alpha
blobs'.
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