[Todos] IAFE -COLOQUIOS: "Towards Ab-initio Cosmological Simulations"

["Area Difusión IAFE"]

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                   PRÓXIMO COLOQUIO DEL IAFE
                 Instituto de Astronomía y Física del Espacio
                           CONICET-UBA
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              "Towards Ab-initio Cosmological Simulations"

                              Justin Read
                         University of Surrey, UK
                   Lunes 2 de setiembre 2013 a las 14:00hs.
                          Aula del Edificio IAFE

The cosmic microwave background radiation gives us a unique snapshot of
the Universe aged just ~400,000 years old. It provides powerful
constraints on our current cosmological model on large scales, suggesting
that most of the Universe is dark: dark matter (~22%) and dark energy
(~74%). However, to probe the nature of dark matter we need to test this
model on smaller scales. This means making cosmological predictions on the
scale of galaxies. I discuss recent progress in raising the realism and
accuracy of such models. I show that the results for cold or
non-relativistic dark matter simulations are robust and converged.
However, in warm dark matter simulations spurious structures form at the
numerical resolution limit. I show that this is a result of force error
and present a novel adaptive force softening that solves the problem. I go
on to discuss the role of gas and stars - baryons - in the Universe. In
the absence of cooling, I show that the simulations are now
well-understood and converged. However, once we allow for radiative
cooling, we must also model star formation and feedback. These rely on
`sub-grid' physics prescriptions that are poorly constrained. I show how
recent high resolution simulations are becoming less sensitive to such
parameters, leading to greater realism and greater predictive power. The
latest results suggest that gas collapse significantly reshapes and
redistributes the dark matter in galaxies. Dark matter halos can both
expand and contract, depending on the mass scale considered; the dark
matter halo shape changes, becoming more spherical; and - for disc
galaxies - accreted satellites lead to the build-up of a dark matter disc.
Building predictive models of such processes is vital if we want to
constrain the nature of dark matter from observations on galactic scales.


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Area Difusión IAFE
Susana Boudemont
susana en iafe.uba.ar
y
Liliana Opradolce
opra en iafe.uba.ar