Sara Rezaei Khoshbakht

Sara Rezaei Khoshbakht (Iran)

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A Gaia-based 3D extinction map of the Galaxy

We present a non-parametric model to mode probabilistically the three-dimensional distribution of dust in the Milky Way. Knowledge of dust distribution in the Galaxy is required when estimating intrinsic stellar properties which are in turn necessary to estimate fundamental quantities like age, origin and structure of the Galaxy. Our model uses line-of-sight extinctions towards stars at different, known positions in the Galaxy. However, unlike many earlier studies which considered each line-of-sight separately, it addresses the correlation structure of dust. Since individual interstellar extinctions are not independent, we use a Gaussian process model to connect these individual lines-ofsight, according to distances between the stars, which gives us the possibility to infer dust densities for any point in 3D space for which no previous extinction information has been presented. Gaia will provide parallaxes to hundreds of millions of stars across the Galaxy to remarkably high accuracy from which stellar distances can be estimated. Interstellar extinctions of these stars will also be estimated using the low resolution spectrophotometry from Gaia. Having the 3D positions of stars as well as their extinctions, we can infer dust densities for areas with no or poor data. It, therefore, reveals the importance of accurate parallax estimation from Gaia on the precision of inferred dust densities.

Supervisor: Coryn Bailer-Jones (MPIA)

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