Detecting Dark Matter in High‐Velocity Clouds

Abstract

Many high-velocity H I clouds (HVCs) are now believed to be scattered throughout the Galactic halo on scales of tens of kiloparsecs. Some of these clouds appear to contain substantial H I masses (>106 Msolar). It has been suggested that these structures may be associated with dark matter ``minihalos'' accreting onto the Galactic halo. For a compact HVC along the sight line to a more distant galaxy, we demonstrate that ``pixel gravitational lensing'' provides a crucial test for the presence of a dark halo in the form of massive compact objects. The detection of pixel lensing will provide an independent means of mapping the mass distribution within HVCs.