Abstract
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.
Highlights
The interstellar extinction attenuates the light coming from background objects
Field Extinction-Distance Relation Deconvolver (FEDReD) compares the apparent photometry of the star to an empirical HertzprungRussel diagram based on a Gaia DR2 representative of local thin disc stars
Once we computed the density of every star P O j | A0, D in the line of sight (LoS), we merged them to obtain an estimate of the joint distribution of extinction and distance of the entire field of view, P (A0, D), using a Bayesian iterative Richardson-Lucy deconvolution (Richardson 1972; Lucy 1974)
Summary
The interstellar extinction attenuates the light coming from background objects. this attenuation is a function of the wavelength of radiation, which causes the reddening phenomenon. Provides photometry in three near-infrared bands: J, H, and Ks. Since Gaia DR2 and 2MASS are full sky surveys, we were able to draw an extinction map of the entire Galactic disc. It looks for P O j | A0, D , in other words, the likelihood of an observed star O j (considering its apparent magnitudes and possibly its parallax) to be at a distance D with extinction A0 (absorption at 550 nm) To compute this probability, FEDReD compares the apparent photometry of the star to an empirical HertzprungRussel diagram based on a Gaia DR2 representative of local thin disc stars. Once we computed the density of every star P O j | A0, D in the LoS, we merged them to obtain an estimate of the joint distribution of extinction and distance of the entire field of view, P (A0, D), using a Bayesian iterative Richardson-Lucy deconvolution (Richardson 1972; Lucy 1974). The white area centred on the Sun corresponds to the too-close distances where the red clump is saturated (see previous section)
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