Planck intermediate results. XLVIII. Disentangling Galactic dust
  emission and cosmic infrared background anisotropies
  Using the Planck 2015 data release (PR2) temperature maps, we separate
Galactic thermal dust emission from cosmic infrared background (CIB)
anisotropies. For this purpose, we implement a specifically tailored
component-separation method, the so-called generalized needlet internal linear
combination (GNILC) method, which uses spatial information (the angular power
spectra) to disentangle the Galactic dust emission and CIB anisotropies. We
produce significantly improved all-sky maps of Planck thermal dust emission,
with reduced CIB contamination, at 353, 545, and 857 GHz. By reducing the CIB
contamination of the thermal dust maps, we provide more accurate estimates of
the local dust temperature and dust spectral index over the sky with reduced
dispersion, especially at high Galactic latitudes above $b = \pm 20{\deg}$. We
find that the dust temperature is $T = (19.4 \pm 1.3)$ K and the dust spectral
index is $\beta = 1.6 \pm 0.1$ averaged over the whole sky, while $T = (19.4
\pm 1.5)$ K and $\beta = 1.6 \pm 0.2$ on 21 % of the sky at high latitudes.
Moreover, subtracting the new CIB-removed thermal dust maps from the
CMB-removed Planck maps gives access to the CIB anisotropies over 60 % of the
sky at Galactic latitudes $|b| > 20{\deg}$. Because they are a significant
improvement over previous Planck products, the GNILC maps are recommended for
thermal dust science. The new CIB maps can be regarded as indirect tracers of
the dark matter and they are recommended for exploring cross-correlations with
lensing and large-scale structure optical surveys. The reconstructed GNILC
thermal dust and CIB maps are delivered as Planck products.
