Spectroscopic Observations of the Fermi Bubbles
  Two giant plasma lobes, known as the Fermi Bubbles, extend 10 kpc above and
below the Galactic Center. Since their discovery in X-rays in 2003 (and in
gamma-rays in 2010), the Bubbles have been recognized as a new morphological
feature of our Galaxy and a striking example of energetic feedback from the
nuclear region. They remain the subject of intense research and their origin
via AGN activity or nuclear star formation is still debated. While imaging at
gamma-ray, X-ray, microwave, and radio wavelengths has revealed their
morphology and energetics, spectroscopy at radio and UV wavelengths has
recently been used to study the kinematics and chemical abundances of
outflowing gas clouds embedded in the Bubbles (the nuclear wind). Here we
identify the scientific themes that have emerged from the spectroscopic
studies, determine key open questions, and describe further observations needed
in the next ten years to characterize the basic physical conditions in the
nuclear wind and its impact on the rest of the Galaxy. Nuclear winds are
ubiquitous in galaxies, and the Galactic Center represents the best opportunity
to study the constitution and structure of a nuclear wind in close detail.
