J/ApJ/891/39 LAMOST DR3 very metal-poor stars of the Galactic halo (Yuan+, 2020)
Dynamical relics of the ancient Galactic halo.
Yuan Z., Myeong G.C., Beers T.C., Evans N.W., Lee Y.S., Banerjee P.,
Gudin D., Hattori K., Li H., Matsuno T., Placco V.M., Smith M.C.,
Whitten D.D., Zhao G.
<Astrophys. J., 891, 39 (2020)>
=2020ApJ...891...39Y 2020ApJ...891...39Y
ADC_Keywords: Stars, metal-deficient; Abundances; Effective temperatures;
Photometry; Optical; Stars, halo
Keywords: Milky Way stellar halo ; Milky Way formation ; R-process
Abstract:
We search for dynamical substructures in the LAMOST DR3 very
metal-poor (VMP) star catalog. After cross-matching with Gaia DR2,
there are ∼3300 VMP stars with available high-quality astrometric
information that have halo-like kinematics. We apply a method based on
the self-organizing map StarGO to find groups clustered in the 4D
space of orbital energy and angular momentum. We identify
57 dynamically tagged groups (DTGs), which we label DTG-1 to DTG-57.
Most of them belong to existing massive substructures in the nearby
halo, such as the Gaia Sausage or Sequoia. The stream identified by
Helmi+ (1999Natur.402...53H 1999Natur.402...53H) is recovered, but the two disjointed
portions of the substructure appear to have distinct dynamical
properties. The very retrograde substructure Rg5 found previously by
Myeong+ (2018MNRAS.478.5449M 2018MNRAS.478.5449M) is also retrieved. We report six new
DTGs with highly retrograde orbits, two with very prograde orbits, and
12 with polar orbits. By mapping other data sets (APOGEE halo stars,
and catalogs of r-process-enhanced and carbon-enhanced metal-poor
[CEMP] stars) onto the trained neuron map, we can associate stars with
detailed chemical abundances with the DTGs and look for associations
with chemically peculiar stars. The highly eccentric Gaia Sausage
groups contain representatives of both debris from the satellite
itself (which is α-poor) and the Splashed Disk, sent up into
eccentric halo orbits from the encounter (and which is α-rich).
The new prograde substructures also appear to be associated with the
Splashed Disk. The DTGs belonging to the Gaia Sausage host two
relatively metal-rich r-II stars and six CEMP stars in different
subclasses, consistent with the idea that the Gaia Sausage progenitor
is a massive dwarf galaxy. Rg5 is dynamically associated with two
highly r-process-enhanced stars with [Fe/H]~-3. This finding indicates
that its progenitor might be an ultrafaint dwarf galaxy that has
experienced r-process enrichment from neutron star mergers.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 97 8117 Cleaned LAMOST DR3 very metal-poor (VMP) star catalog
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See also:
III/279 : RAVE 5th data release (Kunder+, 2017)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
V/153 : LAMOST DR4 catalogs (Luo+, 2018)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/A+A/523/A17 : Individual stars in Fornax dSph center (Letarte+, 2010)
J/A+A/511/L10 : Abundances and space velocities of 94 stars (Nissen+, 2010)
J/ApJ/778/56 : Hamburg/ESO Survey extremely metal-poor stars (Cohen+, 2013)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/ApJ/794/58 : Metal-poor stars in the Galaxy thick disk (Beers+, 2014)
J/ApJ/786/74 : EW measurements of 6 Segue 1 red giants (Frebel+, 2014)
J/A+A/572/A88 : Measured EWs for Fornax RGB stars (Lemasle+, 2014)
J/ApJ/797/21 : Carbon-enhanced metal-poor stars (Placco+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/A+A/579/A28 : Abundances of 3 CEMP stars (Bonifacio+, 2015)
J/AJ/150/187 : Abundances & stellar parameters of LAMOST stars (Lee+, 2015)
J/ApJ/833/20 : Carbon-enhanced metal-poor star abundances (Yoon+, 2016)
J/ApJ/838/44 : Abund. of the brightest member of Tuc III (Hansen+, 2017)
J/ApJ/858/92 : RPA Southern Pilot Search of 107 Stars (Hansen+, 2018)
J/ApJS/238/16 : LAMOST-DR3 very metal-poor star catalog (Li+, 2018)
J/AJ/156/179 : r-process-enhanced field stars kinematics (Roederer+, 2018)
J/ApJ/868/110 : R-Process Alliance: 1st release in Gal. halo (Sakari+, 2018)
J/A+A/623/A128 : Gal. halo CEMP stars abundances & kinematics (Hansen+, 2019)
J/MNRAS/484/2832 : Proper motions of MW globular clusters (Vasiliev, 2019)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- LAMOST Star name (JHHMMSS.ss+DDMMSS.s)
21- 26 F6.3 mag g0mag [7.78/18.98]? De-reddened g-band magnitude
28- 33 F6.3 mag (g-r)0 [-0.19/2.94]? g-r color, de-reddened
35- 38 I4 K Teff [3609/7381] Surface effective temperature (1)
40- 42 I3 K e_Teff [0/424] Uncertainty in Teff (1)
44- 48 F5.3 [cm/s2] logg [0.14/4.77] log of surface gravity (1)
50- 54 F5.3 [cm/s2] e_logg [0/1.3] Uncertainty in logg (1)
56- 61 F6.3 [-] [Fe/H] [-4.4/-1.8] Metallicty (1)
63- 67 F5.3 [-] e_[Fe/H] [0/1.16] Uncertainty in [Fe/H] (1)
69- 74 F6.3 [-] [C/Fe] [-2.02/4.81] log C/Fe abundance ratio (1)
76- 80 F5.3 [-] e_[C/Fe] [0.05/1.3] Uncertainty in [C/Fe]
82- 82 A1 --- f_[C/Fe] Detection flag on [C/Fe] (2)
84- 89 F6.3 [-] [a/Fe] [-0.2/0.6]? log α/Fe abundance ratio (1)
91- 95 F5.3 [-] e_[a/Fe] [0.02/0.3]? Uncertainty in [a/Fe]
97- 97 A1 --- f_[a/Fe] Detection flag on [a/Fe] (2)
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Note (1): Estimates from the n-SSPP, a modified version of the SEGUE Stellar
Parameter Pipeline.
Note (2): Detection flags as follows:
D = detections;
U = upper limits;
L = lower limits;
N = non-detections.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Aug-2021