Determining distances to stars statistically from photometry

In determining the distances to starswithin the Milky Waygalaxy, one often uses photometric or spectroscopic parallax. In these methods, the type of each individual staris determined, and the absolute magnitudeof that startype is compared with the measured apparent magnitudeto determine individual distances. In this article, we define the term statistical photometric parallax, in which statistical knowledge of the absolute magnitudesof stellar populationsis used to determine the underlying density distributions of those stars. This technique has been used to determine the density distribution of the Milky Waystellar halo and its component tidal streams, using very large samples of starsfrom the Sloan Digital Sky Survey. Most recently, the volunteer computing platform MilkyWay@homehas been used to find the best fit modelparameters for the density of these halo stars.