GSH 006-15+7: A local Galactic supershell featuring transition from HI emission to absorption

TL;DR

This paper reports the discovery and analysis of a nearby large Galactic supershell, GSH 006-15+7, revealing its properties, origin, and role in transferring mass and energy from the Galactic disk to the halo.

Contribution

It presents the first detailed characterization of GSH 006-15+7, including its size, mass, and formation energy, using HI emission and absorption data.

Findings

GSH 006-15+7 is one of the nearest large supershells at ~1.5 kpc.

The shell has a mass of approximately 3 million solar masses.

Evidence suggests a formation energy of about 10^52 ergs.

Abstract

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.