From stars to clusters to galaxies to clusters of galaxies
Over the coming decade the astrophysics community will witness an unprecedented revolution in the amount and quality of high-resolution multi-wavelength data on galaxies and their constituents, the result of massive international infrastructure investments in space-borne and ground-based great observatories and experiments. Our proposal aims to exploit this strategic opportunity for the University of Strasbourg to build an ambitious and unifying science-driven project. We propose to take advantage of our highly complementary scientific and technical expertise covering the sub-disciplines of galaxies, stars, interstellar medium, high-energy processes and huge data bases to forge a project to study “galactic ecosystems”, which we define as the dynamical, evolving system of the inter-relations between the constituents of galaxies.
Most importantly, however, we believe that many of the most fundamental and far-reaching questions that astrophysics is confronted with today can best be resolved by studying galaxies as a dynamic whole. Such an approach is necessary because of the complex interactions between a galaxy’s constituent structures. For instance, to understand the chemo-dynamical growth of a galaxy, it is necessary to understand the cosmological accretion that feeds the galaxy, the dynamics of the interstellar medium, the cooling of gas and dust into star-forming regions, the ejection of stellar winds, the production of supernovae and their ensuing ejecta, and the formation of supermassive black holes. The feedback from these energetic processes creates galactic chimneys and fountains, filling a hot gaseous halo, and regulating the further accretion of cosmological gas. So to understand the chemical enrichment of galaxies, we are obliged to follow closely the exchange of matter through these various physical stages which range spatially from scales of hundreds of kiloparsec down to a few hundreds of AU, and to follow a similarly huge range in temperature, pressure, mass, etc. The endeavour therefore requires the fusion of expertise from a wide range of sub-disciplines, wavelength specialisations and analysis methods. Similar arguments hold for all other projects in the science of complex systems.
Despite its complexity, the potential rewards of the approach are great: it will allow us to better understand the formation and evolution of galaxies and their constituent structures, contribute to the understanding of the mysterious dark matter, probe the event horizon of black holes, and follow the cycle of matter through cosmic time, among numerous other fundamentally important issues.