Halo streams in the 7th SDSS data release
  We have detected stellar halo streams in the solar neighborhood using data
from the 7th public data release of the Sloan Digital Sky Survey (SDSS), which
includes the directed stellar program SEGUE: Sloan Extension For Galactic
Understanding and Exploration. In order to derive distances to each star, we
used the metallicity-dependent photometric parallax relation from Ivezic et al.
(2008) for which we examine and quantify the accuracy. Our final sample
consists of 22,321 nearby (d < 2 kpc), metal-poor ([Fe/H] < -0.5) main-sequence
stars with 6D estimates of position and space velocity. We characterize the
orbits of these stars through suitable kinematic proxies for their "effective"
integrals of motion, angular momentum, eccentricity, and orbital polar angle
and compare the observed distribution to expectations from a smooth
distribution in four [Fe/H] bins. On this basis we identify at least five
significant "phase-space overdensities" of stars on very similar orbits in the
solar neighborhood to which we can assign unambiguously peaked [Fe/H]
distributions. Three of them have been identified previously, including the
halo stream discovered by Helmi et al. (1999) at a significance level of 12.0.
In addition, we find at least two new genuine halo streams, judged by their
kinematics and [Fe/H], at significance levels of 2.9 and 4.8, respectively. For
one stream the stars even show coherence in configuration space, matching a
spatial overdensity of stars found by Juric et al. (2008) at (R,z) \approx
(9.5,0.8) kpc. Our results demonstrate the practical power of our search method
to detect substructure in the phase-space distribution of nearby stars without
making a-priori assumptions about the detailed form of the gravitational
potential.
