The impact of bars on disk breaks as probed by S4G imaging

TL;DR

This study investigates how bars influence disk break features in galaxy stellar distributions, revealing that stellar migration driven by bars and resonances significantly shapes disk profiles across different galaxy masses.

Contribution

It provides new insights into the relationship between bars, resonances, and disk breaks, emphasizing the role of stellar migration in galaxy disk structure.

Findings

Disks with single exponential profiles have intermediate scale-lengths and brightness.

The ratio Rbr/Rbar peaks at ~2 and ~3.5 for massive galaxies, linked to resonances.

Radial stellar migration can explain disk breaks at various radii.

Abstract

We have analyzed the radial distribution of old stars in a sample of 218 nearby face-on disks, using deep 3.6um images from the Spitzer Survey of Stellar Structure in Galaxies (S4G). In particular, we have studied the structural properties of those disks with a broken or down-bending profile. We find that, on average, disks with a genuine single exponential profile have a scale-length and a central surface brightness which are intermediate to those of the inner and outer components of a down-bending disk with the same total stellar mass. In the case of barred galaxies, the ratio between the break and the bar radii (Rbr/Rbar) depends strongly on the total stellar mass of the galaxy. For galaxies more massive than 10^10 Msun, the distribution is bimodal, peaking at Rbr/Rbar~2 and ~3.5. The first peak, which is the most populated one, is linked to the Outer Lindblad Resonance of the bar, whereas the second one is consistent with a dynamical coupling between the bar and the spiral pattern. For galaxies below 10^10 Msun, breaks are found up to ~10 Rbar, but we show that they could still be caused by resonances given the rising nature of rotation curves in these low-mass disks. While not ruling out star formation thresholds, our results imply that radial stellar migration induced by non-axysymmetric features can be responsible not only for those breaks at 2 Rbar, but also for many of those found at larger radii.