Spiral density wave triggering of star formation in SA and SAB galaxies

TL;DR

This study investigates how spiral density waves in certain galaxies trigger star formation, analyzing color gradients and resonance locations to support density wave theory.

Contribution

It provides observational evidence linking spiral density waves to star formation triggering and determines pattern speeds and resonance positions in multiple galaxies.

Findings

Most galaxies show color gradients consistent with density wave predictions.

Spiral arms extend to the outer Lindblad resonance in most cases.

Resonance analysis supports the role of density waves in star formation.

Abstract

Azimuthal color (age) gradients across spiral arms are one of the main predictions of density wave theory; gradients are the result of star formation triggering by the spiral waves. In a sample of 13 spiral galaxies of types A and AB, we find that 10 of them present regions that match the theoretical predictions. By comparing the observed gradients with stellar population synthesis models, the pattern speed and the location of major resonances have been determined. The resonance positions inferred from this analysis indicate that 9 of the objects have spiral arms that extend to the outer Lindblad resonance (OLR); for one of the galaxies, the spiral arms reach the corotation radius. The effects of dust, and of stellar densities, velocities, and metallicities on the color gradients are also discussed.