Water in the early Universe

Nuclear environments of galaxies are difficult to observe. Dense clouds containing dust inhibit observational access to these interesting regions at optical or ultraviolet wavelengths. Observations in the far infrared or at X-rays do not provide the required angular resolution to map the innermost parts of galaxies hosting supermassive nuclear engines. However, the 1.3-cm line of water vapor, the strongest spectral line at radio wavelengths, is ideal for such studies. The line permits observations under normal weather conditions, helps to detect water in external galaxies, and allows us to map its distribution with submilliarcsecond resolution. As a consequence, nuclear accretion disks can be mapped, their morphology and size can be evaluated, and direct “geometrical” distances of galaxies can be obtained. In the future, this may lead to the determination of the expansion rate of the local Universe with unprecedented accuracy and to new constraints to the equation of state of the dark energy. In the following, we report the detection of water in the early Universe. This result was obtained by a Ph.D. student of the Max-Planck-Institut für Radioastronomie at Bonn, employing the 100-m telescope at Effelsberg for the original detection and the Very Large Array in New Mexico for confirmation.