Simulating Reionization: Character and Observability

In recent years there has been considerable progress in our understanding of the nature and properties of the reionization process. In particular, the numerical simulations of this epoch have made a qualitative leap forward, reaching sufficiently large scales to derive the characteristic scales of the reionization process and thus allowing for realistic observational predictions. Our group has recently performed the first such large-scale radiative transfer simulations of reionization, run on top of state-of-the-art simulations of early structure formation. This allowed us to make the first realistic observational predictions about the Epoch of Reionization based on detailed radiative transfer and structure formation simulations. We discuss the basic features of reionization derived from our simulations and some recent results on the observational implications for the high-redshift Ly-alpha sources.Comment: 3 pages, to appear in the Proceedings of First Stars III, Santa Fe, July 2007, AIP Conference Serie

XMM-Newton observations of NGC 253: Resolving the emission components in the disk and nuclear area

The high XMM-Newton throughput allows a detailed investigation of the spatial, spectral and variability properties of the extended and point source emission of the starburst galaxy NGC 253 simultaneously. We characterize the brightest sources by their hardness ratios, detect a bright X-ray transient, and show the spectrum and light curve of the brightest point source, most likely a black-hole X-ray binary. The unresolved emission of two disk regions can be modeled by two thin thermal plasma components of 0.13 and 0.4 keV plus residual harder emission, with the lower temperature component originating from above the disk, the nuclear spectrum by a three temperature plasma (~0.6, 0.9, and 6 keV) with the higher temperatures increasingly absorbed. The high temperature component most likely originates from the starburst nucleus. No non-thermal component, that would point at a significant contribution from an active nucleus (AGN), is needed. Assuming that type IIa supernova remnants (SNRs) are mostly responsible for the E>4 keV emission, the detection with EPIC of the 6.7 keV line allows us to estimate a supernova rate within the nuclear starburst of 0.2 yr^-1. RGS spectra and EPIC images reveal that the limb-brightening of the plume is mostly seen in higher ionization emission lines, while in the lower ionization lines, and below 0.5 keV, the plume is more homogeneously structured. (abridged

Fundamental cosmological observations and data interpretation

ISBN 978364200791