Validations and corrections of the SFD and Planck maps
  Precise correction of dust reddening is fundamental to obtain the intrinsic
parameters of celestial objects. The Schlegel et al. (SFD) and the Planck 2D
extinction maps are widely used for the reddening correction. In this work,
using accurate reddening determinations of about two million stars from the
Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) data release
5 (DR5) and Gaia DR2, we check and calibrate the SFD and Planck maps in the
middle and high Galactic latitudes. The maps show similar precision in
reddening correction. We find small yet significant spatially dependent biases
for the four maps, which are similar between the SFD and Planck2014-R maps, and
between the Planck2014-Tau and Planck2019-Tau maps. The biases show a clear
dependence on the dust temperature and extinction for the SFD and Planck2014-R
maps. While those of the Planck2014-Tau and Planck2019-Tau maps have a weak
dependence on the dust temperature, they both strongly depend on the dust
spectral index. Finally, we present corrections of the SFD and Planck
extinction maps within the LAMOST footprint, along with empirical relations for
corrections outside the LAMOST footprint. Our results provide important clues
for the further improvement of the Galactic all-sky extinction maps and lay an
significant foundation for the accurate extinction correction in the era of
precision astronomy.
