Unveiling the Structure of Barred Galaxies at 3.6 $\mu {\rm m}$ with the
  Spitzer Survey of Stellar Structure in Galaxies (S$^4$G): I. Disk Breaks
  We have performed two-dimensional multicomponent decomposition of 144 local
barred spiral galaxies using 3.6 $\mu {\rm m}$ images from the Spitzer Survey
of Stellar Structure in Galaxies. Our model fit includes up to four components
(bulge, disk, bar, and a point source) and, most importantly, takes into
account disk breaks. We find that ignoring the disk break and using a single
disk scale length in the model fit for Type II (down-bending) disk galaxies can
lead to differences of 40% in the disk scale length, 10% in bulge-to-total
luminosity ratio (B/T), and 25% in bar-to-total luminosity ratios. We find that
for galaxies with B/T $\geq$ 0.1, the break radius to bar radius, $r_{\rm
br}/R_{\rm bar}$, varies between 1 and 3, but as a function of B/T the ratio
remains roughly constant. This suggests that in bulge-dominated galaxies the
disk break is likely related to the outer Lindblad Resonance (OLR) of the bar,
and thus moves outwards as the bar grows. For galaxies with small bulges, B/T
$<$ 0.1, $r_{\rm br}/R_{\rm bar}$ spans a wide range from 1 to 6. This suggests
that the mechanism that produces the break in these galaxies may be different
from that in galaxies with more massive bulges. Consistent with previous
studies, we conclude that disk breaks in galaxies with small bulges may
originate from bar resonances that may be also coupled with the spiral arms, or
be related to star formation thresholds.
