Mid- and far-infrared properties of Spitzer Galactic bubbles revealed by
  the AKARI all-sky surveys
  We have carried out a statistical study on the mid- and far-infrared (IR)
properties of Galactic IR bubbles observed by Spitzer. Using the Spitzer 8
${\mu}{\rm m}$ images, we estimated the radii and covering fractions of their
shells, and categorized them into closed, broken and unclassified bubbles with
our data analysis method. Then, using the AKARI all-sky images at wavelengths
of 9, 18, 65, 90, 140 and 160 ${\mu}{\rm m}$, we obtained the spatial
distributions and the luminosities of polycyclic aromatic hydrocarbon (PAH),
warm and cold dust components by decomposing 6-band spectral energy
distributions with model fitting. As a result, 180 sample bubbles show a wide
range of the total IR luminosities corresponding to the bolometric luminosities
of a single B-type star to many O-type stars. For all the bubbles, we
investigated relationships between the radius, luminosities and luminosity
ratios, and found that there are overall similarities in the IR properties
among the bubbles regardless of their morphological types. In particular, they
follow a power-law relation with an index of $\sim$3 between the total IR
luminosity and radius, as expected from the conventional picture of the
Str$\rm{\ddot{o}}$mgren sphere. The exceptions are large broken bubbles; they
indicate higher total IR luminosities, lower fractional luminosities of the PAH
emission, and dust heating sources located nearer to the shells. We discuss the
implications of those differences for a massive star-formation scenario.
