A substructure inside spiral arms, and a mirror image across the Galactic Meridian

TL;DR

The paper identifies a mirror-image substructure within the Milky Way's spiral arms, revealing four distinct lanes with specific gas and dust features, challenging or refining existing galactic density wave models.

Contribution

It uncovers a previously unrecognized mirror-image substructure inside the Milky Way's spiral arms, detailing four distinct lanes with specific physical characteristics.

Findings

Mirror-image substructure across the Galactic Meridian

Four lanes with distinct gas and dust properties

Reveals detailed internal structure of spiral arms

Abstract

While the galactic density wave theory is over 50 years old and well known in science, whether it fits our own Milky Way disk has been difficult to say. Here we show a substructure inside the spiral arms. This substructure is reversing with respect to the Galactic Meridian (longitude zero), and crosscuts of the arms at negative longitudes appear as mirror images of crosscuts of the arms at positive longitudes. Four lanes are delineated: mid-arm (extended 12CO gas at mid arm, HI atoms), in-between offset by about 100 pc (synchrotron, radio recombination lines), in between offset by about 200 pc (masers, colder dust), and inner edge (hotter dust seen in Mid-IR and Near-IR).