Bibcode
Klement, R.; Rix, H.-W.; Flynn, C.; Fuchs, B.; Beers, T. C.; Allende Prieto, C.; Bizyaev, D.; Brewington, H.; Lee, Y. S.; Malanushenko, E.; Malanushenko, V.; Oravetz, D.; Pan, K.; Re Fiorentin, P.; Simmons, A.; Snedden, S.
Referencia bibliográfica
The Astrophysical Journal, Volume 698, Issue 1, pp. 865-894 (2009).
Fecha de publicación:
6
2009
Revista
Número de citas
74
Número de citas referidas
65
Descripción
We have detected stellar halo streams in the solar neighborhood using
data from the seventh public data release of the Sloan Digital Sky
Survey (SDSS), which includes the directed stellar program Sloan
Extension For Galactic Understanding and Exploration (SEGUE). In order
to derive distances to each star, we used the metallicity-dependent
photometric parallax relation from Ivezić et al. We examine and
quantify the accuracy of this relation by applying it to a set of
globular and open clusters observed by the SDSS/SEGUE and comparing the
resulting sequence to the fiducial cluster sequences obtained by An et
al. Our final sample consists of 22,321 nearby (d <= 2 kpc),
metal-poor ([Fe/H] <=-0.5) main-sequence stars with six-dimensional
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. at a significance level of
σ = 12.0. In addition, we find at least two new genuine halo
streams, judged by their kinematics and [Fe/H], at σ = 2.9 and
4.8, respectively. For one stream the stars even show coherence in the
configuration space, matching a spatial overdensity of stars found by
Juric et al. at (R, z) ≈ (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.