Reading the metal diaries of the universe : tracing cosmic chemical evolution from the reionization epoch till the present

Metals are essential for star formation and their subsequent evolution, and ultimately the formation of planets and the development of life, as we know it. Reconstructing the cosmic history of metals, reaching from the first population of stars to the processes involved in the formation of galaxies and clusters of galaxies, is the framework of this White Paper. Most baryons reside in diffuse structures, in (proto)-galaxies and clusters of galaxies, and are predicted to trace the vast filamentary structures created by Dark Matter and Dark Energy. X-ray spectroscopy of diffuse matter has the unique capability of simultaneously probing all the elements (C through Fe), in all their ionization stages and all binding states (atomic, molecular, and solid), and thus provides a model-independent survey of the metals. A medium-size cosmology mission, Xenia – named for the Greek word for hospitality – will combine cryogenic imaging spectrometers and wide field X-ray optics with fast repointing to collect essential information from three major tracers of these cosmic structures: the Warm Hot Intergalactic Medium (WHIM), Galaxy Clusters, and Gamma Ray Bursts (GRBs).