The relation between dynamics and star formation in barred galaxies

TL;DR

This study investigates the connection between star formation and galaxy dynamics in barred spiral galaxies by analyzing color and age gradients, deriving pattern speeds, and comparing them with theoretical expectations.

Contribution

It introduces a method to link observed star formation gradients with galaxy dynamics, estimating pattern speeds and resonance locations in barred galaxies.

Findings

Color/age gradients suggest star formation triggering in bars and spirals.

Derived pattern speeds tend to overestimate true speeds near corotation due to non-circular motions.

Most galaxies show similar pattern speeds for bars and spirals, indicating linked dynamics.

Abstract

We analyze optical and near-infrared data of a sample of 11 barred spiral galaxies, in order to establish a connection between star formation and bar/spiral dynamics. We find that 22 regions located in the bars, and 20 regions in the spiral arms beyond the end of the bar present azimuthal color/age gradients that may be attributed to star formation triggering. Assuming a circular motion dynamic model, we compare the observed age gradient candidates with stellar populations synthesis models. A link can then be established with the disk dynamics that allows us to obtain parameters like the pattern speed of the bar or spiral, as well as the positions of resonance radii. We subsequently compare the derived pattern speeds with those expected from theoretical and observational results in the literature (e.g., bars ending near corotation). We find a tendency to overestimate bar pattern speeds derived from color gradients in the bar at small radii, away from corotation; this trend can be attributed to non-circular motions of the young stars born in the bar region. In spiral regions, we find that ~ 50% of the color gradient candidates are "inverse", i.e., with the direction of stellar aging contrary to that of rotation. The other half of the gradients found in spiral arms have stellar ages that increase in the same sense as rotation. Of the 9 objects with gradients in both bars and spirals, six (67%) appear to have a bar and a spiral with similar Omega_p, while three (33%) do not.