3D Stellar Reddening Map from 2MASS Photometry: An Improved Version
  An improved version of the 3D stellar reddening map in a space with a radius
of 1200 pc around the Sun and within 600 pc of the Galactic midplane is
presented. As in the previous 2010 and 2012 versions of the map, photometry
with an accuracy better than $0.05^m$ in the $J$ and $K_s$ bands for more than
70 million stars from the 2MASS catalogue is used in the new version. However,
the data reduction technique is considerably more complicated. As before, an
analysis of the distribution of stars near the main-sequence turnoff on the
$(J-K_s)$ - $K_s$ diagram, where they form a distribution maximum, provides a
basis for the method. The shift of this maximum, i.e., the $mode(J-K_s)$, along
$(J-K_s)$ and $K_s$, given the spatial variations of the mean de-reddened color
$(J-K_s)_0$ of these stars, is interpreted as a growth of the reddening with
increasing distance. The main distinction of the new method is that instead of
the fixed mean absolute magnitude, de-reddened color, distance, and reddening
for each cell, the individual values of these quantities are calculated for
each star by iterations when solving the system of equations relating them.
This has allowed one to increase the random accuracy of the map to $0.01^m$ and
its spatial resolution to 20 pc in coordinates and distance and to $1^{\circ}$
in longitude and latitude. Comparison with other reddening estimates for the
same spatial cells and Gaia DR1 TGAS stars shows that the constructed map is
one of the best maps for the space under consideration. Its systematic errors
have been estimated to be $\sigma(E(J-K_s))=0.025^m$, or
$\sigma(E(B-V))=0.04^m$. The main purpose of the map is to analyze the
characteristics of Galactic structures, clouds, and cloud complexes. For this
purpose, the reddening map within each spatial cell has also been computed by
analyzing the reddening along each line of sight.
