Helium and Iron in X-ray galaxy clusters

I discuss the role of the sedimentation of helium in galaxy cluster cores on the observed X-ray properties and present a history of the metal accumulation in the ICM, with new calculations with respect to my previous work following the recent evidence of a bi-modal distribution of the delay time in Supernovae Type Ia.Comment: 6 pages. To appear in the Proceedings of "Heating vs. Cooling in Galaxies and Clusters of Galaxies", August 2006, Garching (Germany

Numerical simulations for performance optimization of a few-cycle terawatt NOPCPA system

We present a systematic numerical design and performance study of an ultra-broadband noncollinear optical parametric chirped pulse amplification (NOPCPA) system. Using a split-step Fourier approach, we model a three-stage amplifier system which is designed for the generation of 7 fs pulses with multi-terawatt peak intensity. The numerical results are compared with recent experimental data. Several important aspects and design parameters specific to NOPCPA are identified, and the values of these parameters required to achieve optimal working conditions are investigated. We identify and analyze wavelength-dependent gain saturation effects, which are specific to NOPCPA and have a strong influence on the parametric amplification process. © Springer-Verlag 2007

The chemical enrichment of the ICM from hydrodynamical simulations

The study of the metal enrichment of the intra-cluster and inter-galactic media (ICM and IGM) represents a direct means to reconstruct the past history of star formation, the role of feedback processes and the gas-dynamical processes which determine the evolution of the cosmic baryons. In this paper we review the approaches that have been followed so far to model the enrichment of the ICM in a cosmological context. While our presentation will be focused on the role played by hydrodynamical simulations, we will also discuss other approaches based on semi-analytical models of galaxy formation, also critically discussing pros and cons of the different methods. We will first review the concept of the model of chemical evolution to be implemented in any chemo-dynamical description. We will emphasise how the predictions of this model critically depend on the choice of the stellar initial mass function, on the stellar life-times and on the stellar yields. We will then overview the comparisons presented so far between X-ray observations of the ICM enrichment and model predictions. We will show how the most recent chemo-dynamical models are able to capture the basic features of the observed metal content of the ICM and its evolution. We will conclude by highlighting the open questions in this study and the direction of improvements for cosmological chemo-dynamical models of the next generation.Comment: 25 pages, 11 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 18; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

Observations of metals in the intra-cluster medium

Because of their deep gravitational potential wells, clusters of galaxies retain all the metals produced by the stellar populations of the member galaxies. Most of these metals reside in the hot plasma which dominates the baryon content of clusters. This makes them excellent laboratories for the study of the nucleosynthesis and chemical enrichment history of the Universe. Here we review the history, current possibilities and limitations of the abundance studies, and the present observational status of X-ray measurements of the chemical composition of the intra-cluster medium. We summarise the latest progress in using the abundance patterns in clusters to put constraints on theoretical models of supernovae and we show how cluster abundances provide new insights into the star-formation history of the Universe.Comment: 28 pages, 12 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 16; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

The x-ray polarimetry view of the accreting pulsar Cen X-3

Galaxie

Reflection-dominated Nuclear X-Ray Emission in the Early-type Galaxy ESO 565-G019

We present the discovery of a reflection-dominated active galactic nucleus (AGN) in the early-type radio-quiet galaxy ESO 565-G019 with Suzaku and Swift/Burst Alert Telescope. The source X-ray spectrum below 10 keV is characteristic of other Compton-thick (CT) AGNs, clearly showing an inverted continuum and prodigious fluorescence iron emission above ~3 keV. A Compton shoulder to the neutral Fe Kα line also appears to be present. There is evidence for long-term hard X-ray flux variability that we associate with changes in the intrinsic AGN power law. More of such reflection-dominated AGNs should be uncovered in the near future with the increased sensitivity of ongoing and new hard X-ray surveys. ESO 565-G019 is hosted in an early-type galaxy whose morphology has been variously classified as either type E or type S0. Only about 20 bona fide CT-AGNs have been identified in the local universe so far, and all exist in host galaxies with late Hubble types (S0 or later). CT columns of nuclear obscuring gas are uncommon in early-type galaxies in the local universe, so confirmation of the exact morphological class of ESO 565-G019 is important. Infrared photometry also shows the presence of large quantities of cool dust in the host, indicative of significant ongoing star formation. ESO 565-G019 may be the first identified local example of minor-merger-driven CT-AGN growth in an early-type host, or may be the result of interaction with its neighboring galaxy ESO 565-G018 in a wide pair