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The role of faint star forming galaxies in cosmic reionization

Jure Japelj

The epoch of cosmic reionization represents an important evolutionary
stage of the Universe marking the formation of the first cosmic structures.
Star forming galaxies have long been considered as the dominant sources of
the cosmic ultraviolet background radiation at early epochs. However,
observing and characterizing the galaxy population with significant ionizing
emission has proven to be challenging. In particular, the fraction of
ionizing radiation that escapes from the local environment to the intergalactic
medium (escape fraction) is poorly known. I will present recent observational
and theoretical efforts to understand the properties of the escape fraction
of the star forming population. It has been often suggested that, on average,
escape fraction could be higher for low-luminosity galaxies. The existent
observational data can provide us with meaningful constraints on the escape
fraction. I will show how these constraints, combined with theoretical modelling,
can help us to test the dependence of escape fraction on galaxy luminosity
and furthermore provide means to better understand the properties of star
forming regions.