The Polycyclic Aromatic Hydrocarbon Mass Fraction on a 10 pc scale in
  the Magellanic Clouds
  We present maps of the dust properties in the Small and Large Magellanic
Clouds (SMC, LMC) from fitting Spitzer and Herschel observations with the
\citet{DL07} dust model. We derive the abundance of the small carbonaceous
grain (or polycyclic aromatic hydrocarbon; PAH) component. The global PAH
fraction (q_pah, the fraction of the dust mass in the form of PAHs) is smaller
in the SMC (1.0$^{+0.3}_{-0.3}$%) than in the LMC (3.3$^{+1.4}_{-1.3}$%). We
measure the PAH fraction in different gas phases (H II regions, ionized gas
outside of H II regions, molecular gas, and diffuse neutral gas). H II regions
appear as distinctive holes in the spatial distribution of the PAH fraction. In
both galaxies, the PAH fraction in the diffuse neutral medium is higher than in
the ionized gas, but similar to the molecular gas. Even at equal radiation
field intensity, the PAH fraction is lower in the ionized gas than in the
diffuse neutral gas. We investigate the PAH life-cycle as a function of
metallicity between the two galaxies. The PAH fraction in the diffuse neutral
medium of the LMC is similar to that of the Milky Way ($\sim4.6$%), while it is
significantly lower in the SMC. Plausible explanations for the higher PAH
fraction in the diffuse neutral medium of the LMC compared to the SMC include:
a more effective PAH production by fragmentation of large grains at higher
metallicity, and/or the growth of PAHs in molecular gas.
