A unified picture of breaks and truncations in spiral galaxies from SDSS and S^{4}G imaging

TL;DR

This study analyzes the surface brightness, color, and stellar mass density profiles of 34 inclined spiral galaxies using SDSS and S^{4}G data, identifying two key features: inner breaks and outer truncations, linked to star formation thresholds and angular momentum limits.

Contribution

It provides a unified observational framework for understanding breaks and truncations in spiral galaxies, proposing different physical origins for each feature.

Findings

Inner break radius at ~8 kpc or 0.77 R_{25}

Outer truncation radius near the galaxy's optical edge (~14 kpc or 1.09 R_{25})

Breaks related to star formation thresholds; truncations linked to maximum stellar angular momentum

Abstract

The mechanism causing breaks in the radial surface brightness distribution of spiral galaxies is not yet well known. Despite theoretical efforts, there is not a unique explanation for these features and the observational results are not conclusive. In an attempt to address this problem, we have selected a sample of 34 highly inclined spiral galaxies present both in the Sloan Digital Sky Survey and in the Spitzer Survey of Stellar Structure in Galaxies. We have measured the surface brightness profiles in the five Sloan optical bands and in the 3.6$\mu m$ Spitzer band. We have also calculated the color and stellar surface mass density profiles using the available photometric information, finding two differentiated features: an innermost break radius at distances of $\sim 8 \pm 1$ kpc [$0.77 \pm 0.06$ $R_{25}$] and a second characteristic radius, or truncation radius, close to the outermost optical extent ($\sim 14 \pm 2$ kpc [$1.09 \pm 0.05$ $R_{25}$]) of the galaxy. We propose in this work that the breaks might be a phenomena related to a threshold in the star formation, while truncations are more likely a real drop in the stellar mass density of the disk associated with the maximum angular momentum of the stars.