ERA-Net_ASTRONET Call 2008_Optimal Exploration of Sub-mm Surveys (TAMASIS)

The formation and evolution of stars and galaxies remain among the big questions in astrophysics, primarily because astrophysical dust hides the fundamental processes from traditional optical telescopes. Much of the optical light generated during these processes is absorbed by the dust, and re-radiated at longer wavelengths, mostly in the submillimetre (submm) and far-infrared (far-IR) part of the electromagnetic spectrum. Because the Universe remains largely unexplored in these wavelengths, large surveys are the prime focus of current far-IR/sub-mm research. Indeed, new instruments like the Herschel Space Observatory (Herschel for short) are predominantly going to be used for surveys, both galactic and extra-galactic. Such surveys are an essential ingredient to test current models of the formation and evolution of stars and galaxies, but have so far lacked sufficient data, both in quality and quantity, to make much progress. Herschel will radically change this situation. To deliver the science from these surveys, however, one needs to go well beyond the capacities of the standard tools that will be offered to observers. In fact, to use the unique capabilities and reach the ultimate performance of detectors such as PACS and SPIRE on Herschel, detailed knowledge of all instrumental artifacts has to be intimately woven into the algorithms used to reconstruct sky maps. To produce these algorithms in an efficient way we propose here to bring together data processing experts, Herschel instruments` experts as well as modelers and data analysis experts. Indeed, accurate and realistic simulations of the submillimeter sky offer a very powerful way to adjust the algorithms to the specific science objectives of the surveys, as well as provide clean test cases to quantify the merits of map-making methods. Similarly, advanced data analysis tools, that can for instance take in multi-wavelength data, are required to estimate the algorithms` performance where it matters the most, i.e. at the instrument detection limit.

The formation and evolution of stars and galaxies remain among the big questions in astrophysics, primarily because astrophysical dust hides the fundamental processes from traditional optical telescopes. Much of the optical light generated during these processes is absorbed by the dust, and re-radiated at longer wavelengths, mostly in the submillimetre (submm) and far-infrared (far-IR) part of the electromagnetic spectrum.Because the Universe remains largely unexplored in these wavelengths, large surveys are the prime focus of current far-IR/sub-mm research. Indeed, instruments like the Herschel Space Observatory (Herschel for short) have predominantly been used for surveys, both galactic and extra-galactic. Such surveys are an essential ingredient to test current models of the formation and evolution of stars and galaxies. TAMASIS brought together data processing experts, Herschel instruments' experts as well as modelers and data analysis experts. Accurate and realistic simulations of the submillimeter sky offer a very powerful way to adjust the algorithms to the specific science objectives of the surveys, as well as provide clean test cases to quantify the merits of map-making methods. The Austrian part of the project was to provide these simulations, where the aim was to use a realistic galaxy formation model in combination with a tool to produce 'lightcones', which are basically cone-shaped volumes containing all galaxies visible from Earth on a patch of sky. The main work was implementing the effect of gravitational lensing, which artificially boosts the light of a fraction of the galaxies, thus significantly affecting statistics like number counts (which are well-observed).Most of the work in the Austrian part of the project consisted in implementing gravitational lensing in the creation of realistic mock maps, and the actual production of such maps to test map-making tools (the TAMASIS work done in Paris and Leiden). This work was fully completed, and besides providing maps for our partners, the implementation of the effects of gravitational lensing has also much improved the actual predictions of models for the formation and evolution of dusty galaxies, notably number counts.