Enhanced dust emissivity power-law index along the western H$\alpha$
  filament of NGC 1569
  We used a data set from AKARI and Herschel images at wavelengths from 7
$\mu$m to 500 $\mu$m to catch the evidence of dust processing in galactic winds
in NGC 1569. Images show a diffuse infrared (IR) emission extending from the
galactic disk into the halo region. The most prominent filamentary structure
seen in the diffuse IR emission is spatially in good agreement with the western
H$\alpha$ filament (western arm). The spatial distribution of the
$F_\mathrm{350}/F_\mathrm{500}$ map shows high values in regions around the
super-star clusters (SSCs) and towards the western arm, which are not found in
the $F_\mathrm{250}/F_\mathrm{350}$ map. The color-color diagram of
$F_\mathrm{250}/F_\mathrm{350}$-$F_\mathrm{350}/F_\mathrm{500}$ indicates high
values of the emissivity power-law index ($\beta_\mathrm{c}$) of the cold dust
component in those regions. From a spectral decomposition analysis on a
pixel-by-pixel basis, a $\beta_\mathrm{c}$ map shows values ranging from
$\sim1$ to $\sim2$ over the whole galaxy. In particular, high
$\beta_\mathrm{c}$ values of $\sim2$ are only observed in the regions indicated
by the color-color diagram. Since the average cold dust temperature in NGC 1569
is $\sim30$ K, $\beta_\mathrm{c}<2.0$ in the far-IR and sub-mm region
theoretically suggests emission from amorphous grains, while
$\beta_\mathrm{c}=2.0$ suggests that from crystal grains. Given that the
enhanced $\beta_\mathrm{c}$ regions are spatially confined by the HI ridge that
is considered to be a birthplace of the SSCs, the spatial coincidences may
indicate that dust grains around the SSCs are grains of relatively high
crystallinity injected by massive stars originating from starburst activities
and that those grains are blown away along the HI ridge and thus the western
arm.
