J/ApJ/886/154 Sgr stream K- & M-giants and BHB stars (Yang+, 2019)
Tracing kinematic and chemical properties of Sagittarius stream by K-giants,
M-giants, and BHB stars.
Yang C., Xue X.-X., Li J., Liu C., Zhang Bo, Rix H.-W., Zhang L., Zhao G.,
Tian H., Zhong J., Xing Q., Wu Y., Li C., Carlin J.L., Chang J.
<Astrophys. J., 886, 154 (2019)>
=2019ApJ...886..154Y 2019ApJ...886..154Y
ADC_Keywords: Stars, M-type; Stars, K-type; Stars, giant; Abundances;
Proper motions; Radial velocities; Stars, distances; Optical
Keywords: Galaxy evolution ; Galaxy formation ; Galaxy stellar halos ;
Galaxy kinematics ; Galaxy dynamics
Abstract:
We characterize the kinematic and chemical properties of ∼3000
Sagittarius (Sgr) stream stars, including K-giants, M-giants, and blue
horizontal branch stars (BHBs), selected from SEGUE-2, Large Sky Area
Multi-Object Fibre Spectroscopic Telescope, and Sloan Digital Sky
Survey separately in Integrals-of-Motion space. The orbit of the Sgr
stream is quite clear from the velocity vector in the X-Z plane. Stars
traced by K-giants and M-giants show that the apogalacticon of the
trailing steam is ∼100kpc. The metallicity distributions of Sgr
K-giants, M-giants, and BHBs indicate that the M-giants are on average
the most metal-rich population, followed by K-giants and BHBs. All of
the K-giants, M-giants, and BHBs indicate that the trailing arm is on
average more metal-rich than the leading arm, and the K-giants show
that the Sgr debris is the most metal-poor part. The α-abundance
of Sgr stars exhibits a similar trend with the Galactic halo stars at
lower metallicity ([Fe/H]≲-1.0dex), and then evolve down to lower
[α/Fe] than disk stars at higher metallicity, which is close to
the evolution pattern of the α-element of Milky Way dwarf
galaxies. We find that VY and metallicity of K-giants have gradients
along the direction of the line of sight from the Galactic center in
the X-Z plane, and the K-giants show that VY increases with
metallicity at [Fe/H]≳-1.5dex. After dividing the Sgr stream into
bright and faint streams according to their locations in equatorial
coordinates, the K-giants and BHBs show that the bright and faint
streams present different VY and metallicities, the bright stream is
on average higher in VY and metallicity than the faint stream.
Description:
The Sgr stream sample consists of K-giants, M-giants, and blue
horizontal branch stars (BHBs).
The K-giants are from Sloan Extension for Galactic Understanding and
Exploration 2 (SEGUE-2; Yanny+, 2009, J/AJ/137/4377) and the fifth
data release of Large Sky Area Multi-Object Fibre Spectroscopic
Telescope (LAMOST DR5; see V/164), and their distances were estimated
by Bayesian method Xue+ (2014, J/ApJ/784/170).
The M-giants are picked up from LAMOST DR5 through a 2MASS+WISE
photometric selection criteria. The distances were calculated through
the (J-K)0 color-distance relation Li+ (2016, J/ApJ/823/59),
Li+ (2019, J/ApJ/874/138), and Zhong+ (2019, J/ApJS/244/8).
The BHBs are chosen from SDSS by color and Balmer line cuts, and their
distances were easy to estimate because of the nearly constant
absolute magnitude of BHB stars (Xue+ 2011, J/ApJ/738/79).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 148 3028 Parameters of Sgr stream stars
table2.dat 125 3028 Orbital parameters of Sgr stream stars
(updated version from the author)
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See also:
V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer- Jones+, 2018)
V/164 : LAMOST DR5 catalogs (Luo+, 2019)
J/AJ/113/634 : The survival of Sagittarius dwarf galaxy (Ibata+ 1997)
J/A+A/465/815 : Abundances of Sgr dSph stars (Sbordone+, 2007)
J/AJ/135/1580 : Element abundances in ten red giants of Car dSph (Koch+, 2008)
J/AJ/136/2050 : SEGUE stellar parameter pipeline. II. (Lee+, 2008)
J/ApJ/684/1143 : BHB candidates in the Milky Way (Xue+, 2008)
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/520/A95 : Abundances of red giants in M54 and Sgr dSph (Carretta+, 2010)
J/A+A/523/A17 : Individual stars in Fornax dSph center (Letarte+, 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/A+A/538/A100 : Abundances red giants in Carina dSph (Lemasle+, 2012)
J/ApJ/751/102 : Equivalent widths of 9 RGB in Carina dSph (Venn+, 2012)
J/ApJ/778/149 : Abundances for 3 stars in Sgr dSph (McWilliam+, 2013)
J/A+A/572/A88 : Measured EWs for Fornax RGB stars (Lemasle+, 2014)
J/ApJ/784/170 : SEGUE K giant survey. II. Distances of 6036 stars (Xue+, 2014)
J/ApJ/805/189 : Highly likely members of the Sgr stream (Hyde+, 2015)
J/other/RAA/15.1154 : M-giant star candidates in LAMOST DR 1 (Zhong+, 2015)
J/ApJ/817/40 : High-resolution NIR spectra of local giants (Feuillet+, 2016)
J/ApJ/823/59 : WISE and 2MASS photometry of M giant stars (Li+, 2016)
J/ApJ/850/96 : PS1 3π RRab stars within Sgr stream (Hernitschek+, 2017)
J/ApJ/844/L4 : PS1 RRab for tracing outer Virgo overdensity (Sesar+, 2017)
J/ApJ/872/58 : Sagittarius stream stars with APOGEE obs. (Hasselquist+, 2019)
J/ApJ/874/138 : Gaia and LAMOST DR4 M giant members of Sgr stream (Li+, 2019)
J/ApJ/880/65 : LAMOST K giants in Galactic halo substructures (Yang+, 2019)
J/ApJS/244/8 : M-type stars in LAMOST DR5 (Zhong+, 2019)
J/ApJ/889/63 : Properties of Sgr Stars (Hayes+, 2020)
J/A+A/638/A104 : Gaia DR2 cand. RR Lyrae of Sgr stream & dwarf (Ramos+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- ID Unique identifier in LAMOST (ObsID) or
SDSS (objID) if recno>1817
21- 39 I19 --- Gaia Solution identifier in Gaia DR2 (Source)
41- 49 A9 --- Type Type (1)
51- 59 F9.5 deg RAdeg Right Ascension (J2000)
61- 69 F9.5 deg DEdeg [-18.71/45.38] Declination (J2000)
71- 75 F5.1 kpc Dist [3.4/105.7] Distance (2)
77- 80 F4.1 kpc e_Dist [0.2/23.5] Uncertainty in Dist
82- 87 F6.1 km/s HRV [-306.1/328.1] Heliocentric radial velocity (3)
89- 92 F4.1 km/s e_HRV [0/88.4] Uncertainty in HRV
94- 99 F6.3 mas/yr pmRA [-7.4/3.1] Gaia DR2 proper motion along RA
101-105 F5.3 mas/yr e_pmRA [0.02/1.1] Uncertainty in pmRA
107-113 F7.3 mas/yr pmDE [-12.6/0.42] Gaia DR2 proper motion along DEC
115-119 F5.3 mas/yr e_pmDE [0.02/1.2] Uncertainty in pmDE
124-128 F5.2 [-] [Fe/H] [-3.5/1]? Metallicity (4)
134-137 F4.2 [-] e_[Fe/H] [0.03/0.3]? Uncertainty in feh
139-143 F5.2 [-] [a/Fe] [-0.4/0.7]? Alpha-element abundance
145-148 F4.2 [-] e_[a/Fe] [0.02/0.08]? Uncertainty in [a/Fe]
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Note (1): Source and object type as follows:
LAMOST KG = K-giant from LAMOST (1659 occurrences)
LAMOST MG = M-giant from LAMOST (158 occurrences)
SDSS BHB = blue horizontal branch stars from SDSS (244 occurrences)
SEGUE KG = K-giant from SEGUE (967 occurrences)
Note (2): We calibrated the distances of K-giants, M-giants, and BHBs with
Gaia DR2 (I/345) parallax. See Section 2.
Note (3): The HRV of the LAMOST K-giants are obtained by the ULySS package
(Wu+ 2011RAA....11..924W 2011RAA....11..924W), HRV of LAMOST M-giants are calculated by
Zhong+ (2019, J/ApJS/244/8), and HRV of SEGUE K-giants and SDSS BHBs are
from SEGUE Stellar Parameter Pipeline (SPSS; Lee+ 2008AJ....136.2022L 2008AJ....136.2022L and
2008AJ....136.2050L 2008AJ....136.2050L).
Note (4): The chemical abundances (the overall metallicity [M/H] and the
abundance of α-element [α/M]) of LAMOST K- and M-giants are
from Zhang+ (2020ApJS..246....9Z 2020ApJS..246....9Z), who introduced a machine-learning
program called Stellar LAbel Machine (SLAM) to transfer the APOGEE
DR15 (Majewski+ 2017AJ....154...94M 2017AJ....154...94M) stellar labels to LAMOST DR5 stars.
The metallicity [Fe/H] of SDSS BHBs and SEGUE K-giants are estimated
by SPSS. Since in the APOGEE data, [M/H] and [Fe/H] are calibrated
using the same method, we use [Fe/H] to represent the metallicity of
all stars and do not to distinguish the [M/H] of LAMOST stars and
[Fe/H] of SDSS/SEGUE stars. See Section 2.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- ID Unique identifier in LAMOST/SDSS
21- 24 F4.2 --- e [0.06/1] Integrals-of-Motion eccentricity
26- 29 F4.2 --- e_e [0/0.35] Uncertainty in e
31- 37 F7.2 kpc a [6.4/5032] Integrals-of-Motion semimajor
axis
39- 45 F7.2 kpc e_a [0.1/2452] Uncertainty in a
47- 52 F6.2 deg l-orb [2.8/359.3] Integrals-of-Motion direction
of the orbital pole, galactic longitude
54- 59 F6.2 deg e_l-orb [0.3/161] Uncertainty in l-orbit
61- 66 F6.2 deg b-orb [8.8/160] Integrals-of-Motion direction of
the orbital pole, galactic latitude
68- 72 F5.2 deg e_b-orb [0.1/51] Uncertainty in b-orbit
74- 79 F6.2 deg lapo [0.8/360] Integrals-of-Motion, angle
between apocenter and the projection of
X-axis on the orbital plane
81- 86 F6.2 deg e_lapo [1.6/163] Uncertainty in lapo
88- 97 F10.2 km2/s2 E [-119656/-2024] Energy
99- 107 F9.2 km2/s2 e_E [732/132671] Uncertainty in E
109- 116 F8.2 kpc.km/s L [240/23095] Angular momentum
118- 125 F8.2 kpc.km/s e_L [26/18455] Uncertainty in L
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Acknowledgements:
Chengqun Yang [ycq at bao.ac.cn]
History:
From electronic version of the journal
Column "e_a" in Table 2 updated by the author.
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Apr-2021