We have detected stellar halo streams in the solar neighborhood using data from the 7 ^ { th } 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 Ivezić et al . ( 42 ) .
We examine and quantify the accuracy of this relation by applying it to a set of globular and open clusters observed by SDSS/SEGUE , and comparing the resulting sequence to the fiducial cluster sequences obtained by An et al . ( 2 ) .
Our final sample consists of 22,321 nearby ( d \leq 2 kpc ) , metal-poor ( [ Fe/H ] \leq - 0.5 ) main-sequence stars with 6D estimates of position and space velocity , ( \vec { r } , \vec { v } ) .
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 .
The metallicities provide an additional dimension in parameter space that is well suited to distinguish tidal streams from those of dynamical origin .
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 \sigma = 12.0 .
In addition , we find at least two new genuine halo streams , judged by their kinematics and [ Fe/H ] , at \sigma = 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 . ( 43 ) 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 .