Contributed Talk - Splinter EScience

Friday, 17 September 2021, 10:20   (virtual ESc)

Deriving the 3D structure of the Milky Way: A fast and scalable Gaussian Process applied to nearby star-formation regions

Thavisha Dharmawardena(1), Coryn Bailer-Jones(1), Morgan Fouesneau(1), Dan Foreman-Mackey(2)
(1) Max Planck Institute for Astronomy; (2) Center for Computational Astrophysics, Flatiron Institute

The detailed 3D distributions of dust and extinction in the Milky Way have long been sought after. Three-dimensional reconstruction from sparse data is a non-trivial problem, but it is essential to understanding the properties of both the stars obscured by dust and the large-scale dynamics and structure of our Galaxy. We present a new fast and scalable model based on Gaussian processes implemented using public python packages that runs on either CPUs or GPUs. We use a Gaussian process latent variable method combined with variational inference to map the Galaxy on parsec scales using data from large surveys including Gaia, 2MASS, and WISE. The model maintains non-decreasing extinction and non-negative densities throughout, which has proven problematic in previous efforts. Once trained, the model can be used to predict both extinction and density structure on the fly. This allows us to view the large-scale structure of the Milky Way while simultaneously peering into individual molecular clouds, and provides insights into multi-scale processes such as fragmentation in molecular clouds and the spiral structure of our Galaxy. We have applied our new model to the Orion, Cygnus, Perseus and Taurus star formation regions to recover detailed 3D density structures and localise small scale regions within them. A number of features that are superimposed in 2D extinction maps are deblended in our 3D dust extinction density maps. For example, we find a large filament on the edge of Orion that may host a number of star clusters. We also identify a coherent structure that may link the Taurus and Perseus regions, and show that Cygnus X is located 1300–1500 pc away, in line with VLBI measurements. By comparing our predicted extinctions to Planck data, we find that known relationships between density and dust processing, where high-extinction lines of sight have the most processed grains, hold up in resolved observations when density is included, and that they exist at smaller scales than previously suggested. This can be used to study the changes in size or composition of dust as they are processed in molecular clouds.