Mapping diffuse interstellar bands in the local ISM on small scales via
  MUSE 3D spectroscopy
  We map the interstellar medium (ISM) including the diffuse interstellar bands
(DIBs) in absorption toward the globular cluster NGC 6397 using VLT/MUSE. This
pilot study demonstrates the power of MUSE for mapping the local ISM on very
small scales which provides a new window for ISM observations. Assuming the
absorbers are located at the rim of the Local Bubble we trace small-scale
variations in NaI and KI as well as in several DIBs structures on the order of
mpc (milliparsec, a few thousand AU). The sightlines defined by binned stellar
spectra are separated by only a few arcseconds and we probe the absorption
within a physically connected region. This analysis utilized the fitting
residuals of individual stellar spectra of NGC 6397 member stars and analyzed
lines from neutral species and several DIBs in Voronoi-binned composite spectra
with high signal-to-noise ratio (S/N). We verify the suitability of the MUSE 3D
spectrograph for such measurements and gain new insights by probing a single
physical absorber with multiple sight lines.
