Mapping the Milky Way's ISM

The goal of this project is to map the large-scale structure of our
Galaxy's interstellar medium. There are many publicly available
radio surveys of the distribution of HI and molecular gas in the
Galactic plane. Our group and others have already shown how
hydrodynamical models can -- in principle -- be used to constrain
the large-scale Galactic potential by comparing model predictions
to the (l,b,v) distribution observed in such surveys. In
particular, such models offer the most direct way of constraining
the length, orientation and pattern speed of the Galactic bar. But
no model is yet able to fit all of the observed features: while the
bar orientation is reasonably well constrained, its strength and
pattern speed are still quite uncertain.

This project will develop the ideas we have recently developed for
searching systematically for "good" potentials and for
understanding how best to model the large-scale kinematics of
instellar gas (Sormani & Magorrian 2015 Sormani, Binney & Magorrian
2015a,b,c). Refinements to be investigated include: using trial
potentials based on stellar number counts or on live N-body models;
simple models of different ISM species; improving the
fingerprinting algorithm used to compare models to observations;
modelling the 3d structure of the gas.

A longer-term goal is to use the gas density distributions provided
by such models as priors for our dust-mapping effort. This will
involve collaborating closely with others who are using stellar
photometry and kinematics to constrain the distribution of the
densest parts of the ISM.