  Galactic infrared (IR) bubbles, which can be seen as shell-like structures at
mid-IR wavelengths, are known to possess massive stars within their shell
boundaries. In our previous study, Hanaoka et al. (2019) expanded the research
area to the whole Galactic plane ($0^{\circ} \leq l \leq 360^{\circ}$, $|b|
\leq 5^{\circ}$) and studied systematic differences in the shell morphology and
the IR luminosity of the IR bubbles between inner and outer Galactic regions.
In this study, utilizing high spatial-resolution data of AKARI and WISE in the
mid-IR and Herschel in the far-IR, we investigate the spatial distributions of
dust components around each IR bubble to discuss the relation between the
star-formation activity and the dust properties of the IR bubbles. For the 247
IR bubbles studied in Hanaoka et al. (2019), 165 IR bubbles are investigated in
this study, which have the Herschel data ($|b| \leq 1^{\circ}$) and known
distances. We created their spectral energy distributions on a pixel-by-pixel
basis around each IR bubble, and decomposed them with a dust model consisting
of polycyclic aromatic hydrocarbons (PAHs), hot dust, warm dust and cold dust.
As a result, we find that the offsets of dust heating sources from the shell
centers in inner Galactic regions are systematically larger than those in outer
Galactic regions. Many of the broken bubbles in inner Galactic regions show
large angles between the offset and the broken shell directions from the
center. Moreover, the spatial variations of the PAH intensity and cold dust
emissivity around the IR bubbles in inner Galactic regions are larger than
those in outer Galactic regions. We discuss these results in light of the
interstellar environments and the formation mechanism of the massive stars
associated with the IR bubbles.
