A three-dimensional extinction map of the Galactic anticentre from multiband photometry

Abstract

We present a three dimensional extinction map in $r$ band. The map has a\nspatial angular resolution, depending on latitude, between 3 -- 9\\,arcmin and\ncovers the entire XSTPS-GAC survey area of over 6,000\\,$\\rm deg^2$ for Galactic\nlongitude $\\rm 140 \\leq$ $l$ $ \\leq 220\\deg$ and latitude $\\rm -40\\leq$ $b$ $\n\\leq 40\\deg$. By cross-matching the photometric catalog of the Xuyi Schmidt\nTelescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC) with those\nof 2MASS and WISE, we have built a multi-band photometric stellar sample of\nabout 30 million stars and applied spectral energy distribution (SED) fitting\nto the sample. By combining photometric data from the optical to the\nnear-infrared, we are able to break the degeneracy between the intrinsic\nstellar colours and the amounts of extinction by dust grains for stars with\nhigh photometric accuracy, and trace the extinction as a function of distance\nfor low Galactic latitude and thus highly extincted regions. This has allowed\nus to derive the best-fit extinction and distance information of more than 13\nmillion stars, which are used to construct the three dimensional extinction\nmap. We have also applied a Rayleigh-Jeans colour excess (RJCE) method to the\ndata using the 2MASS and WISE colour $(H-W2)$. The resulting RJCE extinction\nmap is consistent with the integrated two dimensional map deduced using the\nbest-fit SED algorithm. However for individual stars, the amounts of extinction\nyielded by the RJCE method suffer from larger errors than those given by the\nbest-fit SED algorithm.\n