2.2.6 Extinction model

Author(s): Annie Robin

The 3D extinction map is based on the Lallement et al. (2019) map derived from Gaia DR2 photometry. This map is valid up to 3 kpc from the Sun in the plane, and about 700 pc at high latitudes. In directions where one expects extinction occurring at larger distances, one makes use of the Marshall et al. (2006) map which exists only for longitudes between -100 and +100 ${}^{\circ }$, and latitudes between -10${}^{\circ }$ and 10${}^{\circ }$. In cases where these 2 maps disagree at the junction ( at about 3 kpc from the Sun), Marshall et al. (2006) extinctions are renormalised assuming that values from Lallement et al. (2019) are more correct, while Marshall et al. (2006) can suffer from systematics. Such discrepancies occur essentially in a few regions at latitudes between 5${}^{\circ }$ and 10${}^{\circ }$(in absolute value).

The interstellar extinction model is applied to Galactic and extragalactic objects. Small scale variations of the extinction are simulated by adding a dispersion on $A_0$ on a star by star basis. This dispersion is 10% of the mean extinction at the distance of the star.