Halo streams in the 7th SDSS data release

We have detected stellar halo streams in the solar neighborh ood using data from the 7 public data release of the Sloan Digital Sky Survey (SDSS), w hich includes the directed stellar program SEGUE: Sloan Extension For Galact ic Understanding and Exploration. In order to derive distances to each star, we used the metallicity-dependent photometric parallax relation from Ivezi ć et al. (2008). We examine and quantify the accuracy of this relation by applying it to a set of globular a nd open clusters observed by SDSS/SEGUE, and comparing the resulting sequence to the fi ducial cluster sequences obtained by An et al. (2008). Our final sample consist s of 22,321 nearby (d ≤ 2 kpc), metal-poor ([Fe/H] ≤ −0.5) main-sequence stars with 6D estimates of position and space velocity, (~r, ~v). We characterize the orbits of these stars through suitable kinematic proxies for their “effective” integral s of motion, angular momentum, eccentricity, and orbital polar angle and compare the o bserved distribution to expectations from a smooth distribution in four [Fe/H] bins. T he metallicities provide an additional dimension in parameter space that is well suited to distinguish tidal streams 1Max-Planck-Institut für Astronomie, Königstuhl 17, D-691 17 Heidelberg; klement,rix@mpia.de 2Tuorla Observatory, V ais al antie 20, FI-21500 PIIKKI O; cfly nn@utu.fi 3Astronomisches Rechen-Institut am Zentrum für Astronomie Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg; fuchs@ari.uni-heidelberg.de 4Department of Physics & Astronomy, CSCE: Center for the Stud y of Cosmic Evolution, and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, E. La nsing, MI 48824, USA; beers,lee@pa.msu.edu 5Department of Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana Slovenia; paola.refiorentin@fmf.uni-lj.si 6Apache Point Observatory, Sunspot, NM 88349, USA; snedden, dmbiz, hjbrew, viktorm, elenam, doravetz, kpan, asimmons@apo.nmsu.edu 7McDonald Observatory and Department of Astronomy, The Univ ersity of Texas, 1 University Station, C1400, Austin, TX 78712-0259, USA; callende@astro.as.utexas.ed u 8Mullard Space Science Laboratory, University College Lond on, Holmbury St. Mary, Surrey RH5 6NT, United Kingdom