FEDReD. II. 3D extinction map with 2MASS and Gaia DR2 data

Aims. We aim to map the 3D distribution of the interstellar extinction of the Milky Way disc up to distances larger than those probed with the Gaia parallax alone.Methods. We applied the FEDReD (Field Extinction-Distance Relation Deconvolver) algorithm to the 2MASS near-infrared photometry together with the Gaia DR2 astrometry and photometry. This algorithm uses a Bayesian deconvolution approach, based on an empirical HR-diagram representative of the local thin disc, in order to map the extinction as a function of distance of various fields of view.Results. We analysed more than 5.6 million stars to obtain an extinction map of the entire Galactic disc within |b | < 0.24°. This map provides information up to 5 kpc in the direction of the Galactic centre and more than 7 kpc in the direction of the anticentre. This map reveals the complete shape of structures that are known locally, such as the Vela complex and the split of the local arm. Furthermore, our extinction map shows many large “clean bubbles”, especially the one in the Sagittarius-Carina complex, and four others, which define a structure that we nickname the butterfly.