Modeling the 3D Milky Way using Machine Learning with Gaia and infrared
  surveys
  The observation of our home galaxy, the Milky Way (MW), is made difficult by
our internal viewpoint. The Gaia survey that contains around 1.6 billion star
distances is the new flagship of MW structure and can be combined with other
large-scale infrared (IR) surveys to provide unprecedented long distance
measurements inside the Galactic plane. Concurrently, the past two decades have
seen an explosion of the use of Machine Learning (ML) methods that are also
increasingly employed in astronomy.
  I will first describe the construction of a ML classifier to improve a widely
adopted classification scheme for Young Stellar Object (YSO) candidates. Stars
being born in dense interstellar environment, the youngest ones that did not
had time to move away from their formation location are a probe of the densest
structures of the interstellar medium. The combination of YSO identification
and Gaia distance measurements then enables the reconstruction of dense cloud
structures in 3D. Our ML classifier is based on Artificial Neural Networks
(ANN) and uses IR data from the Spitzer space telescope to reconstruct the YSO
classification automatically from given examples.
  In a second part, I will propose a new method for reconstructing the 3D
extinction distribution of the MW based on Convolutional Neural Networks (CNN).
The CNN is trained using a large-scale Galactic model, the Besan\c{c}on Galaxy
Model, and learns to infer the extinction distance distribution by comparing
results of the model with observed data. This method is able to resolve distant
structures up to 10 kpc with a formal resolution of 100 pc, and was found to be
capable of combining 2MASS and Gaia datasets without the necessity of a cross
match. The results from this combined prediction are encouraging and open the
possibility for future full Galactic plane prediction using a larger
combination of various datasets.
