The local spiral structure of the Milky Way

TL;DR

This study uses radio measurements to map the Milky Way's Local spiral arm, revealing it is larger and more similar to major arms than previously thought, with implications for understanding galactic structure.

Contribution

It provides new distance measurements of star-forming regions, showing the Local Arm's size, shape, and star formation rate are comparable to major spiral arms, refining galactic models.

Findings

The Local Arm is larger than previously estimated.

The Local Arm's pitch angle and star formation rate are similar to major arms.

Identification of a spur between the Local and Sagittarius arms.

Abstract

The nature of the spiral structure of the Milky Way has long been debated. Only in the last decade have astronomers been able to accurately measure distances to a substantial number of high-mass star-forming regions, the classic tracers of spiral structure in galaxies. We report distance measurements at radio wavelengths using the Very Long Baseline Array for eight regions of massive star formation near the Local spiral arm of the Milky Way. Combined with previous measurements, these observations reveal that the Local Arm is larger than previously thought, and both its pitch angle and star formation rate are comparable to those of the Galaxy's major spiral arms, such as Sagittarius and Perseus. Toward the constellation Cygnus, sources in the Local Arm extend for a great distance along our line of sight and roughly along the solar orbit. Because of this orientation, these sources cluster both on the sky and in velocity to form the complex and long enigmatic Cygnus X region. We also identify a spur that branches between the Local and Sagittarius spiral arms.