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Centro de Astrofísica da Universidade do Porto
How Lyman alpha radiation gets out of galaxies (or not)

G÷ran Ístlin
Stockholm University

Abstract
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.

21 May 2015, 13:30

Centro de AstrofÝsica
Rua das Estrelas
4150-762 Porto

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

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