Interferometry in astronomy

Interferometry is a powerful tool in astronomy used for sky observations with increased spatial resolution and sensitivity. Here, I demonstrate these capabilities using two leading world-class representatives of both radio and optical interferometry, namely the IRAM interferometer and the GRAVITY instrument at the Very Large Telescope Interferometer. GRAVITY observes two sky objects simultaneously at wavelengths of ~ 2 µm. Measuring the differential optical path difference (dOPD) between both signals for pairs of telescopes provides the intrinsic phase of the science object as well as its angular separation to the reference target, known as phase-referenced imaging and narrow-angle astrometry. For this purpose, the internal dOPDs in the instrument and observatory need to be measured with nanometer accuracy. This is realized by a laser metrology based on phase-shifting interferometry. The IRAM interferometer provided a first large statistical census of the molecular gas in distant galaxies at the peak of cosmic star formation. On this basis, I studied spatially-resolved molecular gas in a small sample of galaxies. I compared the morphology of the molecular gas with the structures of stellar continuum, stellar mass and star-formation rate. Furthermore, I extracted the kinematics of the molecular gas. While similar studies are frequently done for the ionized-gas component on large statistical samples, the corresponding analysis of molecular gas is still rather rare