J/ApJ/698/865 Halo streams in the SDSS-DR7 (Klement+, 2009)
Halo streams in the seventh Sloan Digital Sky Survey data release.
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.
<Astrophys. J., 698, 865-894 (2009)>
=2009ApJ...698..865K 2009ApJ...698..865K
ADC_Keywords: Abundances, [Fe/H] ; Photometry, SDSS ; Stars, halo ;
Radial velocities ; Stars, distances
Keywords: Galaxy: kinematics and dynamics - solar neighborhood
Abstract:
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 Ivezic et al. (2008ApJ...684..287I 2008ApJ...684..287I).
Our final sample consists of 22321 nearby (d≤2kpc), metal-poor
([Fe/H]≤-0.5) main-sequence stars with six-dimensional estimates of
position and space velocity (r{vec},ν{vec}). 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.
(1999MNRAS.307..495H 1999MNRAS.307..495H) 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.
Description:
SDSS-I was an imaging and spectroscopic survey that began routine
operations in 2000 April and continued through 2005 June. The SDSS,
and its extensions, uses a dedicated 2.5m telescope located at the
Apache Point Observatory in New Mexico.
One of three subsurveys carried out during the first extension of the
SDSS, known as SDSS-II, the Sloan Extension for Galactic Understanding
and Exploration (SEGUE), ran from 2005 July to 2008 June. SEGUE
obtained some 250000 medium-resolution spectra of stars in the
Galaxy.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 70 7 Main characteristics of the stellar streams
considered real
table3.dat 102 278 Putative members of the identified streams:
astrophysical parameters
table4.dat 108 206 Putative members of the identified streams:
photometry and velocities
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See also:
II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
J/AJ/136/2070 : SEGUE stellar parameter pipeline. III. (Allende Prieto+, 2008)
J/AJ/134/1579 : Halo stars in solar neighborhood (Kepley+, 2007)
http://www.sdss.org/ : Sloan Digital Sky Survey (SDSS) home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Stream Stream designation
6- 20 A15 --- Aut Author's reference
22- 40 A19 --- BibCode Bibcode reference
42- 45 I4 km/s Vaz Azimuthal velocity (Vaz) (1)
47- 49 I3 km/s VdelE VΔE parameter (2)
51- 53 I3 deg nu Orbital inclination (ν)
55- 58 F4.1 --- Sig Significance of the stream obtained as
described in Section 6
60- 61 I2 --- N Number of putative stream members
63- 66 F4.1 [Sun] <[Fe/H]> Mean metallicity of the stream
68- 70 F3.1 [Sun] e_<[Fe/H]> <[Fe/H]> standard deviation
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Note (1): The azimuthal velocity of a star is given by (U,V,W are the
cartesian components of the velocity): Vaz2=(V+VLSR)2+W2
Note (2): The parameter VΔE parametrizes the difference between
the energy of a star at the guiding center of its orbit and at the
solar radius, and is a measure of its orbital eccentricity:
VΔE2=U2+2(VLSR-Vaz)2; the eccentricity is then
e=2-1/2.VΔE/VLSR
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Stream Stream designation (G1)
6- 9 A4 --- --- [SDSS]
11- 29 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS.s)
31- 34 I4 --- Plate SDSS plate
35 A1 --- --- [-]
36- 40 I5 --- MJD SDSS modified Julian date
41 A1 --- --- [-]
42- 44 I3 --- Fiber SDSS fiber
46- 56 F11.7 deg RAdeg Right ascension in decimal degrees (J2000)
58- 68 F11.7 deg DEdeg Declination in decimal degrees (J2000)
70- 75 F6.3 [Sun] [Fe/H] Fe/H abundance
77- 81 F5.3 [Sun] e_[Fe/H] Fe/H uncertainty (1)
83- 86 I4 K Teff Effective temperature
88- 90 I3 K e_Teff Teff uncertainty (1)
92- 96 F5.3 [cm/s2] logg Surface gravity
98-102 F5.3 [cm/s2] e_logg logg uncertainty (1)
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Note (1): The errors on [Fe/H], Teff, and logg are internal estimates,
obtained from averaging of multiple techniques.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Stream Stream designation (G1)
6- 9 A4 --- --- [SDSS]
11- 29 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS.s)
31- 36 F6.3 mag umag SDSS u-band AB magnitude
38- 43 F6.3 mag gmag SDSS g-band AB magnitude
45- 50 F6.3 mag rmag SDSS r-band AB magnitude
52- 57 F6.3 mag i'mag SDSS i'-band AB magnitude
59- 64 F6.3 mag z'mag SDSS z'-band AB magnitude
66- 70 F5.3 kpc Dist Estimated distance
72- 76 F5.3 kpc e_Dist 1σ error in Dist
78- 87 F10.5 km/s HRV Heliocentric radial velocity
89- 94 F6.1 km/s U U component radial velocity (1)
96-101 F6.1 km/s V V component radial velocity
103-108 F6.1 km/s W W component radial velocity (1)
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Note (1): Stars of the RAVE DR-1 stream possess high vertical and low
radial velocity components, =121±2km/s and =24±2km/s
(Paper I, Klement et al., 2008ApJ...685..261K 2008ApJ...685..261K, section 6).
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Global notes:
Note (G1): The last two entries in the bottom of the list are stars that
appear in both "S3" and "C2", and both "S3" and "C3", respectively.
The reason is that our selection criteria for "C2", "C3" and "S3" show
some overlap. Also, we already noted in Section 7.4 and Section 7.6
that a connection between these streams probably exists.
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History:
From electronic version of the journal
References:
Klement et al. Paper I: Identifying stellar streams in the First RAVE
Public Data Release (2008ApJ...685..261K 2008ApJ...685..261K)
(End) Emmanuelle Perret [CDS] 07-Jun-2011