Astronomy Tea Talks at Caltech

"Dynamical distances to high-velocity clouds"
High-velocity clouds (HVCs) are pockets of neutral hydrogen that reside in
abundance in the Galactic halo and have velocities that cannot be
explained by a simple model of differential Galactic rotation. These HI
clouds do not harbour stars, making it challenging to determine distances
to them. For some HVCs, lower and/or upper distance limits have been
derived through the interstellar absorption line technique. I will
present some rather different and complementary approaches to determining
distances to these HI clouds, in particular those that exhibit stream-like
appearances. These methos primarily use knowledge of the radial velocity
of the clouds, together with the assumption of them following orbits in a
suitable Galactic potential. We have successfully applied the simplest
method to the Magellanic stream and generalise this method in order to
apply them to the numerous, shorter, less coherent HVC streams that can be
identified in all-sky HI maps.