Interaction of the Galactic-Centre Super Bubbles with the Gaseous Disc

TL;DR

This paper investigates how the Galactic-Centre super bubbles interact with the Milky Way's gaseous disc and halo, revealing their structure, formation, and the impact of past explosive events on the galaxy's gas distribution.

Contribution

It provides a new unified model of the Galactic-Centre super bubbles' structure and formation mechanism based on multi-wavelength survey data.

Findings

GSB forms a GC-symmetrical Ω shape.

Gas density increases sharply at the 3-kpc crater.

Crater formed by a shock wave from a past explosion ~10 My ago.

Abstract

The interaction of Galactic-Centre (GC) super bubbles (GSB) with the gaseous disc and halo of the Milky Way is investigated using radio continuum, X-ray, HI and CO line surveys. The radio North Polar Spur (NPS) constitutes the brightest eastern ridge of GSB, brightening towards the galactic plane and reaching $ l = 22\deg, \ b = + 2\deg$ at the sharpest end, where it intersects the tangential direction of the 3-kpc expanding ring and crater. Examination of the spur ridges reveals that the entire GSB, including the NPS and its counter spurs, constitutes a GC-symmetrical $\Omega /$\rotatebox[origin=c]{180}{$\Omega$} shape. The thickness and gas density of the HI and CO discs are shown to increase sharply from the inside (lower longitude) to the outside of the 3-kpc crater. Formation of crater is explained by the sweeping of the upper layer of disc gas by the shock wave from the GC by the explosion $ \sim 10 $ My ago with the emitted energy of several $10 ^ {55} $ ergs. Based on the discussion, a unified view on the structure and formation mechanism of GSB is presented.