SecondPeriodProjectB3 - TransRegio

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B3 - Supernovae probing the Dark Energy

Principal Investigators: Wolfgang Hillebrandt (Garching); Bruno Leibundgut (Garching); Friedrich Röpke (Garching; until December 2010)

Project B3 investigates the physics and astrophysics of Type Ia supernovae in order to check for systematic effects which might limit their usefulness in constraining the cosmic expansion history H(z) out to a redshift of about 2. In addition, guided by theory, the high-quality data emerging from present and future supernova surveys will be used to reconstruction H(z) without further model assumptions.

Type Ia supernovae, in their unprecedented capability as distance indicators, are the only direct proof of the accelerated expansion of the universe. The are now employed to probe the equation of state of the dark energy throughout a large fraction of the history of the universe. They are currently the only means to map the expansion history of the universe out to a redshift of about 1 and to identify the influence of the dominating energy density. The combination of distances from the local universe to beyond a look-back time of half the history of the universe gives potentially the best leverage on dark energy and its changes, if any.

Several projects have been finished, are under way, or are planned to observe SNe Ia at all redshifts, starting from very nearby ones to search for systematic effects in their calibration, at intermediate redshifts, and also very high redshifts, the aim being to determine the equation of state parameter of dark energy and, possibly, also its first derivative. In contrast, model independent ways of interpreting the data have be developed recently. They require high data quality if applied to constrain models of the dark energy. Guided by theoretical modeling we will make an attempt create such a data set from existing supernova data and from those to come. In addition, the model-independent approach will also be applied to baryon acoustic oscillation data as an independent way to get H(z).

100s_scaled.jpg sa2_scaled.jpg
Three-dimensional hydrodynamical simulation of a SNIa explosion. The first image shows the density distribution 100s after the explosion. The second image shows color-coded the distribution chemical composition of the same simulation. Blue corresponds to unburned material, redder color intermediate mass elements like magnesium, silicon and sulfur, the yellow region corresponds to material rich in iron group elements.

With our re fined numerical codes LEAFS (combustion hydrodynamics) and ARTIS (Monte-Carlo radiative-transfer) we are in a position to perform 'parameter-free' numerical simulations of SNe Ia explosions and to predict the physical quantities which are needed for the investigation of systematic e ffects of metallicity, age and environment on their lightcurves and spectra, as well as di fferent progenitor systems. In particular we investigate the question of whether the observed correlation between peak-luminosity and light-curve shape and other similar correlations can be understood in the framework of the explosion models and, thus, can be made more reliable and robust. Moreover, we will start a search of which parameters are crucial in determining the correlations.

Publications (2nd funding period)>>>
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