The Hercules-Aquila Cloud

We present evidence for a substantial overdensity of stars in the direction of the constellations of Hercules and Aquila. The cloud is centered at a Galactic longitude of l~40^deg and extends above and below the Galactic plane by at least 50°. Given its off-centeredness and height, it is unlikely that the Hercules-Aquila cloud is related to the bulge or thick disk. More likely, this is a new structural component of the Galaxy that passes through the disk. The cloud stretches ~80° in longitude. Its heliocentric distance lies between 10 and 20 kpc so that the extent of the cloud in projection is ~20 kpc by ~15 kpc. It has an absolute magnitude of M_v=-13, and its stellar population appears to be comparable to, but somewhat more metal-rich than, M92.