Shedding light on the Epoch of Reionization with the 21cm signal

Wed 7th Aug 2019 @14:15 PM, level 7, David Caro Building
Dr Anne Hutter



The Epoch of Reionization represents an important epoch in the history
in the Universe, when the first stars and galaxies gradually ionize the
neutral hydrogen in the intergalactic medium (IGM). Understanding the
nature of the ionizing sources, the associated ionization of the IGM,
and its impact on subsequent structure formation and galaxy evolution by
means of radiative feedback effects, represent key outstanding questions
in current astrophysics.

In the past few years high-redshift galaxy observations and simulations
have significantly extended our knowledge on the nature of high-redshift
galaxies. However, essential properties such as the escape fraction of
ionizing photons from galaxies into the intergalactic medium and their
dependency on galactic properties remain essentially unknown, but
determine significantly the distribution and time evolution of the
ionized regions during reionization. Analysing this ionization topology
by means of the neutral hydrogen sensitive 21cm signal with radio
interferometers such as the Square Kilometre Array (SKA) offers a
complementary and unique opportunity to determine the nature of these
first galaxies and pin down the reionization history.

In this talk, I will discuss how synergising high-redshift galaxy
observations with 21cm signal detections can provide constraints on
reionization. Furthermore, I will show results from a self-consistent
semi-numerical model of galaxy evolution and reionization, and discuss
the potential of inferring galactic properties, as the escape fraction
of ionizing photons, with the 21cm signal by means of its bispectrum.

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