Galactic HI supershells: Kinetic energies and possible origin
  The Milky Way, when viewed in the neutral hydrogen line emission, presents
large structures called Galactic supershells (GSs). The origin of these
structures is still a subject of debate. The most common scenario invoked is
the combined action of strong winds from massive stars and their subsequent
explosion as supernova. The aim of this work is to determine the origin of 490
GSs that belong to the Catalog of HI supershell candidates in the outer part of
the Galaxy. To know the physical processes that took place to create these
expanding structures, it is necessary to determine their kinetic energies. To
obtain all the GS masses, we developed and used an automatic algorithm, which
was tested on 95 GSs whose masses were also estimated by hand. The estimated
kinetic energies of the GSs vary from $1\times10^{47}$ to $3.4\times10^{51}$
erg. Considering an efficiency of 20% for the conversion of mechanical stellar
wind energy into the kinetic energy of the GSs, the estimated values of the GS
energies could be reached by stellar OB associations. For the GSs located at
high Galactic latitudes, the possible mechanism for their creation could be
attributed to collision with high velocity clouds (HVC). We have also analysed
the distribution of GSs in the Galaxy, showing that at low Galactic latitudes,
$|b|<2^\circ$, most of the structures in the third Galactic quadrant seem to be
projected onto the Perseus Arm. The detection of GSs at very high distances
from the Galactic centre may be attributed to diffuse gas associated with the
circumgalactic medium of M31 and to intra-group gas in the Local Group
filament.
