Three-dimensional extinction mapping of the Milky Way faces a fundamental trade-off: Gaia's precise astrometry and photometry enable high-resolution mapping but only to limited distances due to visible-wavelength extinction, while infrared surveys like 2MASS penetrate deeper into the Galactic plane but provide poor distance constraints, especially in the solar neighbourhood. Many studies have cross-matched these surveys in order to provide more wavelength coverage and therefore better extinction estimates. This comes at a cost as the cross-matching limits depth to the visible survey's reach, as highly extinguished stars detected in infrared lack visible counterparts. We develop PyRedLine as an evolution of the REDLINE method, enabling simultaneous exploitation of multiple surveys without cross-matching. Our goal is to achieve both high spatial resolution at short distances through Gaia and extended reach into the Galactic plane through 2MASS, with target resolution of ~100pc within several kpc. PyRedLine compares statistical distributions of observed stellar properties (colours, parallaxes, absolute magnitudes) against predictions from the Besancon Galaxy Model reddened by parameterised extinction profiles. Using Bayesian inference with MCMC sampling, we independently determine extinction along each LOS by fitting model predictions to Gaia DR3 and 2MASS observations simultaneously, then assemble these profiles into three-dimensional maps. Validation with synthetic data confirms reliable structure detection to ~8kpc. We successfully map the Galactic plane from 240{deg}<=l<=303{deg} and |b|<=5{deg} at 15' resolution. The resulting map reveals extinction to 13kpc with up to 42pc resolution. We recover known structures including the Vela molecular complex and Carina arm tangent, achieving significantly finer resolution at short distances compared to REDLINE while maintaining comparable depth. We detect distant features potentially associated with the Perseus arm that remain undetected in other surveys.
Cone search capability for table J/A+A/710/A344/list (List of 3D extinction map fits datacubes)
