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How Lyman alpha radiation gets out of galaxies (or not)

Göran Östlin
Stockholm University

The Lyman alpha emission line is the strongest transition of hydrogen, the most abundant element in galaxies and the universe. With a rest wavelength in the far ultraviolet it is conveniently accesible for ground based observations at redshifts z > 2, and consequently, Lyman alpha is one of the most used probes to find and determine the redshift of the distant galaxy population.
However, Lyman alpha is a resonant line and sensitive to scattering on neutral hydrogen. Hence the transport of Lyman alpha photons through a galaxy is a complex process that is affected by the structure and kinematics of the ISM in galaxies, things which are difficult to measure in distant galaxies. This introduce biases and hampers the use of Lyman alpha as a quantitative probe of the physics of distant galaxies.
The Lyman Alpha Reference Sample (LARS) is a suite of projects aimed at a detailed investigation of Lyman alpha physics in the nearby universe, where galaxies can be resolved at greater detail than at high redshifts. I will review what LARS has taught us about Lyman alpha escape from galaxies and what the remaining challenges are.

2015 May 21, 13:30

Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto

Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia