J/ApJ/880/65 LAMOST K giants in Galactic halo substructures (Yang+, 2019)
Identifying Galactic halo substructure in 6D phase space using ∼13000
LAMOST K giants.
Yang C., Xue X.-X., Li J., Zhang L., Liu C., Zhao G., Chang J., Tian H.,
Li C.
<Astrophys. J., 880, 65 (2019)>
=2019ApJ...880...65Y 2019ApJ...880...65Y
ADC_Keywords: Stars, giant; Stars, halo; Stars, K-type; Stars, distances;
Radial velocities; Proper motions; Associations, stellar; Optical
Keywords: Galaxy: evolution ; Galaxy: formation ; Galaxy: halo ;
Galaxy: kinematics and dynamics
Abstract:
We construct a large halo K-giant sample by combining the positions,
distances, radial velocities, and metallicities of over 13000 LAMOST
DR5 halo K giants with the Gaia DR2 proper motions, which covers a
Galactocentric distance range of 5-120kpc. Using a position-velocity
clustering estimator (the 6Distance), we statistically quantify the
presence of position-velocity substructure at high significance:
K giants have more close pairs in position-velocity space than a
smooth stellar halo. We find that the amount of substructure in the
halo increases with increasing distance and metallicity. With a
percolation algorithm named friends-of-friends to identify groups, we
identify members belonging to Sagittarius (Sgr) Streams, Monoceros
Ring, Virgo Overdensity, Hercules-Aquila Cloud, Orphan Streams, and
other unknown substructures and find that the Sgr streams account for
a large part of grouped stars beyond 20kpc and enhance the increase of
substructure with distance and metallicity. For the first time, we
identify spectroscopic members of Monoceros Ring in the southern and
northern Galactic hemispheres, which presents a rotation of about
185km/s and a mean metallicity of -0.66dex.
Description:
LAMOST DR5 combining with Gaia DR2 enables us to construct a large
sample of 13554 halo K giants with distances up to 100kpc, radial
velocities, metallicities, and proper motions (see Section 2).
Finally, we find 43 friends-of-friends (FoF) groups (1867 group
members), in which 25 groups belong to five known substructures:
Sgr Stream (13 groups), Monoceros Ring (4 groups), Virgo Overdensity
(4 groups), Hercules-Aquila Cloud (3 groups), and Orphan Stream (1
group); and 18 remaining groups are likely related to unknown
substructures. See Section 5.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 110 7 Known Substructures in LAMOST halo K giants
table4.dat 92 18 Unknown groups in LAMOST halo K giants
table5.dat 63 1867 Group member catalog in groups with five or
more members
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See also:
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/164 : LAMOST DR5 catalogs (Luo+, 2019)
J/ApJ/588/824 : Veloc. of blue stars near (l,b)=(198,-27) (Yanny+, 2003)
J/A+A/493/71 : UBV photometry of Shorlin 1 (Carraro+, 2009)
J/MNRAS/398/1757 : RR Lyraes in SDSS stripe 82 (Watkins+, 2009)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/ApJ/714/663 : Stellar density map of the Milky Way (de Jong+, 2010)
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/other/RAA/11.924 : Atmospheric parameters for 771 stars (Wu+, 2011)
J/ApJ/738/79 : SDSS-DR8 BHB stars in the Milky Way's halo (Xue+, 2011)
J/MNRAS/422/2116 : BHB & RR Lyrae towards Anticentre and NGP (Kinman+, 2012)
J/ApJ/776/26 : RRab stars in the Orphan stream distances (Sesar+, 2013)
J/ApJS/213/9 : Catalina Surveys periodic variable stars (Drake+, 2014)
J/A+A/566/A118 : Comprehensive view of Virgo stellar stream (Duffau+, 2014)
J/ApJ/784/170 : SEGUE K giant survey. II. Distances (Xue+, 2014)
J/ApJ/816/80 : SEGUE K giant survey. III. Galactic halo (Janesh+, 2016)
J/ApJ/844/L4 : RRab for tracing outer Virgo overdensity (Sesar+, 2017)
J/ApJ/836/5 : Abundances of LAMOST giants from APOGEE DR12 (Ho+, 2017)
J/ApJS/245/34 : LAMOST DR5 abundances for 6 million stars (Xiang+, 2019)
Byte-by-byte Description of file: table[34].dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Group [0/41] Group identifier
4- 9 F6.2 deg RAdeg [-8/336] Right ascension, minimum (J2000)
11- 16 F6.2 deg RAMdeg [5/353] Right ascension, maximum (J2000)
18- 22 F5.2 deg DEdeg [-6/35] Declination, minimum (J2000)
24- 28 F5.2 deg DEMdeg [8/61] Declination, maximum (J2000)
30- 34 F5.2 kpc Distm [6/78] Distance, minimum
36- 40 F5.2 kpc DistM [17/96] Distance, maximum
42- 48 F7.2 km/s HRVm [-330/118] Heliocentric radial velocity,
minimum
50- 56 F7.2 km/s HRVM [-203/289] Heliocentric radial velocity,
maximum
58- 62 F5.2 mas/yr pmRA [-7/1.4] Proper motion in right ascension,
minimum
64- 68 F5.2 mas/yr pmRAM [-1/4.2] Proper motion in right ascension,
maximum
70- 74 F5.2 mas/yr pmDE [-7.5/-0.1] Proper motion in declination,
minimum
76- 80 F5.2 mas/yr pmDEM [-2.1/0.9] Proper motion in declination, max
82- 86 F5.2 [-] [Fe/H]m [-2.5/-1.5] Log of Fe/H abundance, minimum
88- 92 F5.2 [-] [Fe/H]M [-1.8/-0.1] Log of Fe/H abundance, maximum
94-110 A17 --- Name Name of the known substructure
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- obsID [203248/584701188] LAMOST observation
identifier (1)
11- 20 F10.6 deg RAdeg Right Ascension (J2000)
22- 30 F9.6 deg DEdeg [-5.7/60.2] Declination (J2000)
32- 38 F7.4 kpc Dist [6.15/96] Distance
40- 46 F7.2 km/s HRV [-329.5/288.3] Heliocentic radial velocity
48- 53 F6.3 mas/yr pmRA [-6.6/4.2] Gaia DR2 proper motion
in Right Ascension
55- 60 F6.3 mas/yr pmDE [-7.5/0.9] Gaia DR2 proper motion
in Declination
62- 63 I2 --- Group [0/24]? Group identifier, as in Table 4 (2)
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Note (1): obsID is a unique identifier in LAMOST.
Note (2): Group identifier codes as follows:
0 = Sagittarius (Sgr) trailing arm (595 occurrences);
1 = Sgr leading arm (477 occurrences);
2 = Monoceros Ring (258 occurrences);
3 = Virgo Overdensity (106 occurrences);
4 = Hercules-Aquila (56 occurrences);
5 = Sgr Debris (17 occurrences);
6 = Orphan Stream (8 occurrences);
>6 = unknown.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 13-Jan-2021