2012MNRAS.421.3159M

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 and in HI self-absorption (HISA) at b ≳ -6°5. We use this feature along with HISA diagnostics to estimate an optical depth of τ ∼ 3, a spin temperature of ∼ 40 K and a swept-up mass of M ∼ 3 {x} 10⁶ M_☉. 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 ∼ 10⁵² erg. We find that this structure provides evidence for the transfer of mass and energy from the Galactic disc into the halo.