SDSS Survey for Resolved Milky Way Satellite Galaxies II: High-Velocity   Clouds in the Early Data Release
  In this paper, we limit the stellar content of 13 high-velocity clouds (HVCs; including 1 compact HVC) using the detection limits of a new survey for resolved Milky Way satellite galaxies in the Sloan Digital Sky Survey Early Data Release (EDR). Our analysis is sensitive to stellar associations within the virial radius of the Milky Way that are up to 50 times fainter than the faintest known Milky Way satellites. Statistically, we find no stellar overdensity associated with any of the clouds. These non-detections suggest lower limits of M_{HI}/L_V that range between ~ 0.2 and 250, assuming cloud distances of 50 and 300 kpc and using fiducial optical scale lengths of 3' and 7'. We explore the implication of these non-detections on the origin of the HVCs. 
Beth Willman, Julianne Dalcanton, Zeljko Ivezic, Donald P. Schneider,   Donald G. York