High–Velocity Clouds: Building Blocks of the Local Group

We suggest that the high–velocity clouds (HVCs) are large clouds, with typical diameters of 25 kpc and containing 5×107 solar masses of neutral gas and 3×108 solar masses of dark matter, falling onto the Local Group; altogether the HVCs contain 10 solar masses of neutral gas. Our reexamination of the Local–Group hypothesis for the HVCs connects their properties to the hierarchical structure formation scenario and to the gas seen in absorbtion towards quasars. We begin by showing that at least one HVC complex (besides the Magellanic Stream) must be extragalactic at a distance >40 kpc from the Galactic center, [email protected] [email protected] [email protected] [email protected] [email protected]