Arm Tangents and the spiral structure of the Milky Way ; the Age Gradient

TL;DR

This study observes an age gradient in the Milky Way's spiral arms using various tracers, supporting density wave theory, and compares these findings with Gaia satellite data to understand arm dynamics.

Contribution

It provides the first measurement of an age gradient in the Milky Way's spiral arms using multiple tracers, confirming theoretical predictions.

Findings

Detected an age gradient of about 12 +/-2 Myrs/kpc in spiral arms.

Estimated dust lane departure speed at approximately 81 +/-10 km/s.

Compared arm tracer data with Gaia observations to analyze spiral structure.

Abstract

From the Sun, a look at the edge of each spiral arm in our Milky Way (seen tangentially, along the line of sight) can yield numerous insights. Using different arm tracers (dust, masers, synchrotron emission, CO gas, open star clusters), we observe here for the first time an age gradient (about 12 +/-2 Myrs/kpc), much as predicted by the density wave theory. This implies that the arm tracers are leaving the dust lane at a relative speed of about 81 +/-10 km/s. We then compare with recent optical data obtained from the Gaia satellite, pertaining to the spiral arms.