J/ApJ/950/142 Orbital param. of the MW thick-disk giant stars (Hu+, 2023)
Angular momentum variation of the Milky Way thick disk: the dependence of
chemical abundance and evidence of the inside-out formation scenario.
Hu G., Shao Z., Li Lu
<Astrophys. J., 950, 142 (2023)>
=2023ApJ...950..142H 2023ApJ...950..142H
ADC_Keywords: Milky Way; Stars, giant; Abundances; Stars, ages;
Stars, diameters; Surveys; Optical; Infrared
Keywords: Milky Way disk ; Milky Way evolution ; Stellar kinematics ;
Dynamical evolution ; Galaxy structure ; Astronomy data analysis ;
Chemical abundances
Abstract:
We investigate the angular momentum of mono-abundance populations
(MAPs) of the Milky Way thick disk by using a sample of 26,076 giant
stars taken from APOGEE Data Release (DR) 17 and Gaia early DR3. The
vertical and perpendicular angular momentum components, LZ and LP, of
the MAPs in narrow bins have significant variations across the
[α/M]-[M/H] plane. LZ and LP systematically change with [M/H]
and [α/M] and can be alternatively quantified by the chemical
gradients: d[M/H]/dLZ=1.2x10-3dex/kpc/km.s,
d[M/H]/dLP=-5.0x10-3dec.kpc-1.km-1.s, and
d[α/M]/dLZ=-3.0x10-4dex.kpc-1.km-1.s,
d[α/M]/dLP=1.2x10-3dec.kpc-1.km-1.s. These correlations
can also be explained as the chemical dependence of the spatial
distribution shape of the MAPs. We also exhibit the corresponding age
dependence of the angular momentum components. Under the assumption
that the guiding radius (Rg) is proportional to LZ, this provides
direct observational evidence of the inside-out structure formation
scenario of the thick disk, with dRg/dAge=-1.9kpc/Gyr. The progressive
changes in the disk thickness can be explained by the upside-down
formation or/and the consequent kinematical heating.
Description:
In HS22 (Hu & Shao, 2022, J/ApJ/929/33), we have identified and
quantified four subdisk components of the MW, by using the chemical
abundances ([M/H], [α/M]) and the 3D velocities (VR , Vφ ,
VZ) taken or derived from APOGEE DR17 and Gaia EDR3 for a sample of
119558 giant stars. We have also calculated the 6D kinematical
information (3D positions and 3D velocities) relative to the Sun, by
using the coordinates and proper motions from Gaia EDR3, the radial
velocities from APOGEE DR17, and the photogeometric distances
estimated by Bailer-Jones+ (2021, I/352).
In this work, we subsequently use the 6D kinematic data as the input
of the GALPOT package to integrate the stellar orbit of each sample
star under the Galactic potential model of McMillan (2017MNRAS.465...76M 2017MNRAS.465...76M).
Thus, we obtain the vertical and perpendicular angular momentum
components LZ and LP. Additionally, we obtain the Galactic pericenter
(rperi) and apocenter (rapo) radii, and then derive the orbital
eccentricity.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 94 26076 Parameters for thick-disk stars
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See also:
V/130 : Geneva-Copenhagen Survey of Solar neighbourhood III (Holmberg+, 2009)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
I/352 : Distances to 1.47 billion stars in Gaia EDR3 (Bailer-Jones+, 2021)
III/286 : APOGEE-2 DR17 final allStar catalog (Abdurro'uf+, 2022)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/572/A33 : Abundances from Gaia-ESO Survey (Mikolaitis+, 2014)
J/ApJ/823/114 : The Cannon: a new approach to determine masses (Ness+, 2016)
J/ApJ/868/133 : j-M relation for disk and bulge type galaxies (Fall+, 2018)
J/MNRAS/489/176 : Dynamical heating across the MW disc (Mackereth+, 2019)
J/ApJ/929/33 : Kinematics of giants from APOGEE & Gaia (Hu+, 2022)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- APOGEE APOGEE DR17 identifier
20- 38 I19 --- Gaia Gaia EDR3 identifier
40- 43 F4.2 [-] [a/M] [0.15/0.35] [α/M] In APOGEE DR17
45- 49 F5.2 [-] [M/H] [-1/-0.1] [M/H] In APOGEE DR17
51- 55 F5.2 Gyr Age [0/12.6]? Age;
Sanders & Das 2018MNRAS.481.4093S 2018MNRAS.481.4093S
57- 60 F4.2 --- phia [0/1] The membership probabilities
belonging to high-α for individual
sample stars (1)
62- 69 F8.2 kpc.km.s-1 LZ [-1958/3291] Vertical angular momentum
component, LZ
71- 77 F7.2 kpc.km.s-1 LP [5.28/2446] Perpendicular angular momentum
component, LP
79- 82 F4.2 --- ecc [0.01/1] Orbital eccentricity
((rapo-rperi)/ (rapo+rperi))
84- 88 F5.2 kpc Rg [0/14.31] Guiding radius, Rg (2)
90- 94 F5.2 kpc Rgc [0.2/17.2] Galactocentric distance
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Note (1): Table 2 of HS22 (Hu & Shao, 2022, J/ApJ/929/33)
Note (2): Usually, the LZ of a star can be transferred to its guiding radius
(Rg), based on the relationship Vφ2/Rg=LZ2/Rg3. We
calculate the Rg for each star under the assumption that the
rotational velocity is a constant across the region covering our
thick-disk sample, with Vφ=230km/s.
See Section 2.2.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 04-Aug-2025