Jens Chluba (Canadian Institute for Theoretical Astrophysics)

Signals from the Cosmological Recombination Epoch

The Planck Surveyor is currently measuring the CMB temperature and polarization anisotropies with unprecedented precision. For the analysis of these data sets it will be very important to understand the ionization history of the Universe at redshift z~1100 with very high accuracy, since otherwise uncertainties in the modelling of the recombination process may lead to significant biases in the deduced values of some cosmological parameters. In addition to the simple fact that free electrons are captured by protons and helium ions also some photons are released in the cosmological recombination process, leading to small distortions in the CMB blackbody spectrum which should still be present today. This recombination radiation carries valuable information about the dynamics of recombination and the underlying cosmological parameters, which until now has not been accessed. In my talk I will discuss some of the recent refinements in connection with the ionization history of the Universe and the CMB power spectra, showing that neglecting details in the physics of recombination will lead to important biases in the values of n_s and Omega_b. Furthermore, I will try to show that one could learn a lot about cosmological parameters, details in the recombination dynamics, energy release at high redshift and possible dark matter annihilations during recombination by directly measuring the cosmological recombination radiation.

Else Starkenburg (Gronigen University)

Title: The satellites of the Milky Way: Insights from modeling and observations

Abstract: There is much to be learned about galaxy formation and evolution from our own Milky Way halo and the dwarf galaxies around it. Resolved stellar spectroscopy presents us with “archeological” evidence about the chemical enrichment of the interstellar medium back to the earliest times. In this talk I will discuss several insights in the (chemical) evolution of the dwarf galaxies around the Milky Way from both modeling and observational perspectives. I will show that the classical dwarf galaxies are not so devoid of extremely low-metallicity stars as was previously thought and discuss how well we can represent the dwarf galaxy satellite system by semi-analytical prescriptions in fully cosmological simulations.