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CfA theory seminars

Tue Jun 1, 12:30pm

Uri Keshet       (Weizmann Institute )

The imprint of intergalactic shocks on the gamma-ray and radio sky

Strong intergalactic shocks are a natural consequence of structure
formation in the universe. Using analytic and numeric (SPH simulation
based) analyses, we show that the non-thermal emission from such shocks
produces a significant fraction of the extra-Galactic radio (ERB) and
gamma-ray (EGRB) backgrounds, as well as anisotropy in the radio
background that dominates on ~1-30 arcminute scales and low (<10 GHz)
frequencies. We re-analyze existing gamma-ray and radio sky maps, finding
that the EGRB is significantly lower than previously estimated, and ruling
out previous claims for direct ERB detection. The predicted signals from
intergalactic shocks should be detectable in the coming few years. For
example, at least several gamma-ray clusters are predicted to be
detectable by GLAST and by ground based Cherenkov telescopes, and the
radio fluctuations are predicted to be detectable by LOFAR and by
SKA. Detection of the signal will allow to identify intergalactic shocks
and probe large-scale flows, will provide a direct detection of the
warm-hot IGM, and may allow to determine the strength and structure of
intergalactic magnetic fields.

The seminar will be held in Pratt Conference Room (G04) of CfA (60 Garden


Wed, Jun 2, 12:30pm

Romeel Dave (Arizona)

Detecting and Quantifying the Warm-Hot Intergalactic Medium

The Warm-Hot Intergalactic Medium (WHIM) contains nearly half of
the baryons in the universe at the present epoch, yet has been
largely overlooked in observational studies.  I will present
an overview of this now-famous Case of the Missing Baryons,
and discuss ways in which this case can be solved by current
and upcoming UV and X-ray observations.  In particular, I will
highlight the role of cosmological hydrodynamic simulations in
predicting, elucidating, and quantifying this important repository
of baryons.

The seminar will be held in Pratt Conference Room (G04) of CfA (60
Garden St.) at 12:30pm.