Fitting the density substructure of the stellar halo with MilkyWay@home
  We propose and test a method for applying statistical photometric parallax to
main sequence turn off (MSTO) stars in the Sloan Digital Sky Survey (SDSS).
Using simulated data, we show that if our density model is similar to the
actual density distribution of our data, we can reliably determine the density
model parameters of three major substructures in the Milky Way halo using the
computational resources available on MilkyWay@home (a twenty parameter fit). We
fit the stellar density in SDSS stripe 19 with a smooth stellar spheroid
component and three major streams. One of these streams is consistent with the
Sagittarius tidal stream at $21.1$ kpc away, one is consistent with the
trailing tail of the Sagittarius tidal stream in the north Galactic cap at $48$
kpc away, and one is possibly part of the Virgo Overdensity at $6$ kpc away. We
find the one sigma widths of these three streams to be $1.0$ kpc, $17.6$ kpc,
and $6.1$ kpc, respectively. The width of the trailing tail is extremely wide
($41$ kpc full width at half maximum). This large width could have implications
for the shape of the Milky Way dark matter halo. The width of the Virgo
Overdensity-like structure is consistent with what we might expect for a
"cloud"-like structure; analysis of additional stripes of data are needed to
outline the full extent of this structure and confirm its association with the
Virgo Overdensity.
