New Constraints on the Origin of Surface Brightness Profile Breaks of Disk Galaxies from MaNGA

摘要

In an effort to probe the origin of surface brightness profile (SBP) breaks widely observed in nearby disk galaxies, we carry out a comparative study of stellar population profiles of 635 disk galaxies selected from the Mapping Nearby Galaxies at Apache Point Observatory spectroscopic survey. We classify our galaxies into single exponential (Ti), down-bending (Tii), and up-bending (Tiii) SBP types and derive their spin parameters and radial profiles of age/metallicity-sensitive spectral features. Most Tii (Tiii) galaxies have down-bending (up-bending) star formation rate (SFR) radial profiles, implying that abrupt radial changes of SFR intensities contribute to the formation of both Tii and Tiii breaks. Nevertheless, a comparison between our galaxies and simulations suggests that stellar migration plays a significant role in weakening down-bending Σ_(?) profile breaks. While there is a correlation between the break strengths of SBPs and age/metallicity-sensitive spectral features for Tii galaxies, no such correlation is found for Tiii galaxies, indicating that stellar migration may not play a major role in shaping Tiii breaks, as is also evidenced by a good correspondence between the break strengths of Σ_(?) and SBPs of Tiii galaxies. We do not find evidence for galaxy spin being a relevant parameter for forming different SBP types, nor do we find significant differences between the asymmetries of galaxies with different SBP types, suggesting that environmental disturbances or satellite accretion in the recent past do not significantly influence the break formation. By dividing our sample into early and late morphological types, we find that galaxies with different SBP types follow nearly the same tight stellar mass– relation, which makes the hypothesis that stellar migration alone can transform SBP types from Tii to Ti and then to Tiii highly unlikely.