Multiplicity of nuclear dust lanes and dust lane shocks in the Milky Way bar

TL;DR

This paper identifies additional inner-galaxy dust lanes and shocks in the Milky Way, suggesting a more complex structure and evolution of gas flow in the galactic bar than previously known.

Contribution

It reports the discovery of a small family of dust lanes and shocks beyond the main ones, expanding understanding of the Milky Way's inner gas dynamics.

Findings

Multiple new dust lanes with peculiar kinematics identified

Associated broad line profiles indicate gas shredding at shocks

Evidence suggests secondary dust lanes and shocks exist in the Milky Way bulge

Abstract

Aims: We show the existence of a small family of inner-galaxy dust lanes and dust lane standing shocks beyond the two major ones that were previously known to exist Methods: We analyze images of CO emission in the inner regions of the Galaxy Results: The peculiar kinematics of the major dust lane features are repeated in several other distinct instances at l > 0deg, in one case at a contrary location 100 pc above the galactic equator at l > 3degr at the upper extremity of Clump 2. Like the previously-known dust lanes, these new examples are alsoassociated with localized, exceptionally broad line profiles believed to be characteristic of the shredding of neutral gas at the standing dust lane shocks. Conclusions: There may be secondary dust lane and standing shocks in the Milky Way bulge. The vertical structure provides a temporal sequence for understanding the secular evolution of gas flow in the bar.