J/ApJ/816/80 The SEGUE K giant survey. III. Galactic halo (Janesh+, 2016)
The SEGUE K giant survey.
III. Quantifying Galactic halo substructure.
Janesh W., Morrison H.L., Ma Z., Rockosi C., Starkenburg E., Xue X.X.,
Rix H.-W., Harding P., Beers T.C., Johnson J., Lee Y.S., Schneider D.P.
<Astrophys. J., 816, 80 (2016)>
=2016ApJ...816...80J 2016ApJ...816...80J (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Stars, K-type ; Abundances, [Fe/H] ;
Photometry, SDSS ; Stars, distances
Keywords: Galaxy: evolution; Galaxy: formation; Galaxy: halo;
Galaxy: kinematics and dynamics
Abstract:
We statistically quantify the amount of substructure in the Milky Way
stellar halo using a sample of 4568 halo K giant stars at
Galactocentric distances ranging over 5-125kpc. These stars have been
selected photometrically and confirmed spectroscopically as K giants
from the Sloan Digital Sky Survey's Sloan Extension for Galactic
Understanding and Exploration (SEGUE) project. Using a
position-velocity clustering estimator (the 4distance) and a model of
a smooth stellar halo, we quantify the amount of substructure in the
halo, divided by distance and metallicity. Overall, we find that the
halo as a whole is highly structured. We also confirm earlier work
using blue horizontal branch (BHB) stars which showed that there is an
increasing amount of substructure with increasing Galactocentric
radius, and additionally find that the amount of substructure in the
halo increases with increasing metallicity. Comparing to resampled BHB
stars, we find that K giants and BHBs have similar amounts of
substructure over equivalent ranges of Galactocentric radius. Using a
friends-of-friends algorithm to identify members of individual groups,
we find that a large fraction (∼33%) of grouped stars are associated
with Sgr, and identify stars belonging to other halo star streams: the
Orphan Stream, the Cetus Polar Stream, and others, including
previously unknown substructures. A large fraction of sample K giants
(more than 50%) are not grouped into any substructure. We find also
that the Sgr stream strongly dominates groups in the outer halo for
all except the most metal-poor stars, and suggest that this is the
source of the increase of substructure with Galactocentric radius and
metallicity.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 74 30 *Selected FoF groups found at linking length
4δ=0.03
table3.dat 91 1192 Group catalog: K giants sorted by group for
groups with 4 or more members
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Note on table2.dat: Group larger than 10 members or identified as notable
structure.
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See also:
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
J/ApJ/764/78 : Oxygen abundances in nearby FGK stars (Ramirez+, 2013)
J/ApJ/738/79 : SDSS-DR8 BHB stars in the Milky Way's halo (Xue+, 2011)
J/ApJ/731/119 : BHB candidates in Sagittarius stream (Ruhland+, 2011)
J/ApJ/718/683 : The edge of the young Galactic disk (Carraro+, 2010)
J/ApJ/703/2177 : Metal-poor MS turnoff stars summary (Schlaufman+, 2009)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/ApJ/684/1143 : BHB candidates in the Milky Way (Xue+, 2008)
J/AJ/135/564 : Photometry and spectroscopy of BHB candidates (Brown+, 2008)
J/AJ/132/714 : QUEST RR Lyrae survey. II. Halo overdensities (Vivas+, 2006)
J/AJ/125/2502 : Spectral indices of Galactic halo (Morrison+, 2003)
J/AJ/117/2308 : Spectroscopy of hot stars in the halo (Wilhelm+, 1999)
J/AJ/100/1191 : Giants DDO photometry (Morrison+, 1990)
http://www.sdss3.org/ : SDSS-III home page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Group [3/483] Group number
5- 7 I3 --- Nm [4/212] Number of members
9- 14 F6.2 deg GLON Galactic longitude (1)
16- 21 F6.2 deg GLAT Galactic latitude (1)
23- 29 F7.2 km/s VGSR [-149.8/153.4] Galactic Standard of Rest
velocity (1)
31- 35 F5.2 kpc Rgc [12.1/90.8] Galacto-centric radius (1)
37- 41 F5.2 [Sun] [Fe/H] [-2.2/-1.1] Abundance of [Fe/H] (1)
43- 72 A30 --- Notes Notes
74 A1 --- f_Notes Flag on Notes (2)
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Note (1): Mean value for all stars in group.
Note (2): Flag as follows:
c = See Belokurov et al. (2007ApJ...657L..89B 2007ApJ...657L..89B); well-matched in l, b,
rgc, [Fe/H], but not vgsr.
d = See Newberg et al. (2003ApJ...596L.191N 2003ApJ...596L.191N).
e = Denoted as SgrP in Z. Ma et al. (2016, in preparation).
f = See Grillmair (2014ApJ...790L..10G 2014ApJ...790L..10G).
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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 I4 --- Plate SDSS plate identifier
6- 10 I5 d MJD Modified Julian Date of SDSS observation
12- 14 I3 --- Fiber SDSS fiber identifier
16- 23 F8.4 deg GLON Galactic longitude
25- 32 F8.4 deg GLAT Galactic latitude
34- 39 F6.1 km/s VGSR [-191.5/209.5] Galactic Standard of Rest velocity
41- 44 F4.1 km/s e_VGSR [0.6/7] Error in VGSR
46- 50 F5.1 kpc Dist [5.5/92] Distance
52- 55 F4.1 kpc e_Dist [0.7/9] Error in Dist
57- 61 F5.2 [-] [Fe/H] [-3.6/0.2] Metallicity
63- 68 F6.3 mag gmag [14.7/19.1] SDSS g band magnitude
70- 74 F5.2 mag rMag [-3.1/0.5] Absolute SDSS r band magnitude
76- 82 F7.3 kpc Rgc [4.8/99.8] Galacto-centric radius
84 I1 --- Type [1/4] Target type (1)
86- 88 I3 --- Group [3/581] Group number
90- 91 I2 --- Flag [3/9] Group identity flag (2)
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Note (1): Target type as follows:
1 = l-color K giants;
2 = proper motion K giants;
3 = red K giants;
4 = serendipitous K giants.
Note (2): Group identity flag as follows:
3 = not Sgr;
4 = unlikely Sgr;
5 = possible Sgr;
6 = definitely Sgr;
7 = Orphan Stream;
8 = Virgo Overdensity;
9 = Cetus Polar Stream.
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History:
From electronic version of the journal
References:
Xue et al., Paper II. 2014ApJ...784..170X 2014ApJ...784..170X, Cat. J/ApJ/784/170
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Mar-2016