The stellar mass distribution of S$^{4}$G disk galaxies

TL;DR

This study uses 3.6 μm imaging from the S$^{4}$G survey to analyze stellar density profiles and bars in disk galaxies, revealing differences related to galaxy type and bar presence, informing galaxy evolution models.

Contribution

It provides the first statistical analysis of stellar density profiles and bar properties across galaxy types using stacked images, highlighting bar-induced secular evolution effects.

Findings

Barred galaxies have larger disk scalelengths and fainter central surface brightness.

Surface brightness profiles of barred and non-barred galaxies intersect near the bar corotation.

Barred galaxies exhibit higher central mass concentration, especially in early-type spirals.

Abstract

We use 3.6 $\mu$m imaging from the S$^{4}$G survey to characterize the typical stellar density profiles ($\Sigma_{\ast}$) and bars as a function of fundamental galaxy parameters (e.g. the total stellar mass $M_{\ast}$), providing observational constraints for galaxy simulation models to be compared with. We rescale galaxy images to a common frame determined by the size in physical units, by their disk scalelength, or by their bar size and orientation. We stack the resized images to obtain statistically representative average stellar disks and bars. For a given $M_{\ast}$ bin ($\ge 10^{9}M_{\odot}$), we find a significant difference in the stellar density profiles of barred and non-barred systems that gives evidence for bar-induced secular evolution of disk galaxies: (i) disks in barred galaxies show larger scalelengths and fainter extrapolated central surface brightnesses, (ii) the mean surface brightness profiles of barred and non-barred galaxies intersect each other slightly beyond the mean bar length, most likely at the bar corotation, and (iii) the central mass concentration of barred galaxies is larger (by almost a factor 2 when $T<5$) than in their non-barred counterparts. We also show that early- and intermediate-type spirals ($0 \le T < 5$) host intrinsically narrower bars than the later types and S0s, whose bars are oval-shaped. We show a clear correlation between galaxy family and bar ellipticity.