GSH 006-15+7: A local Galactic supershell featuring transition from HI
  emission to absorption
  We report on the discovery of a new Galactic supershell, GSH 006-15+7, from
the Galactic All Sky Survey data. Observed and derived properties are presented
and we find that GSH 006-15+7 is one of the nearest physically large
supershells known, with dimensions of ~ 780 x 520 pc at a distance of ~ 1.5
kpc. The shell wall appears in HI emission at b <~ -6.5 deg and in HI
self-absorption (HISA) at b >~ -6.5 deg. We use this feature along with HISA
diagnostics to estimate an optical depth of tau ~ 3, a spin temperature of ~ 40
K and a swept-up mass of M ~ 3e6 solar masses. We also investigate the origin
of GSH 006-15+7, assessing the energy contribution of candidate powering
sources and finding evidence in favour of a formation energy of ~ 1e52 ergs. We
find that this structure provides evidence for the transfer of mass and energy
from the Galactic disk into the halo.
