J/ApJ/878/21 Vertical motions of APOGEE & Gaia red clump stars (Ting+, 2019)
The vertical motion history of disk stars throughout the Galaxy.
Ting Y.-S., Rix H.-W.
<Astrophys. J., 878, 21-21 (2019)>
=2019ApJ...878...21T 2019ApJ...878...21T (SIMBAD/NED BibCode)
ADC_Keywords: Abundances; Stars, ages; Stars, distances
Keywords: Galaxy: disk; Galaxy: evolution; Galaxy: kinematics and dynamics
Galaxy: structure; methods: data analysis; methods: statistical
Abstract:
It has long been known that the vertical motions of Galactic disk
stars increase with stellar age, commonly interpreted as vertical
heating through orbit scattering. Here we map the vertical actions of
disk stars as a function of age (τ≤8Gyr) and across a large range
of Galactocentric radii, RGC, drawing on APOGEE and Gaia data. We
fit Jz(RGC,τ) as a combination of the vertical action at
birth, Jz,0, and the subsequent heating ΔJz,1Gyr(RGC),
which scales as τγ(RGC_)^. The inferred birth temperature,
Jz,0(RGC) is 1kpc.km/s for 3kpc<RGC<10kpc, consistent with the
ISM velocity dispersion, but it rapidly rises outward, to 8kpc.km/s
for RGC=14kpc, likely reflecting the stars' birth in a warped or
flared gas disk. We find the heating rate ΔJz,1Gyr to be
modest and nearly constant across all radii, 1.6kpc.km/s/Gyr. The
stellar age dependence γ gently grows with Galactocentric
radius, from γ∼1 for RGC≲R☉ to γ∼1.3 at
RGC=14kpc. The observed Jz-τ relation at all radii is
considerably steeper (γ≳1) than the time dependence
theoretically expected from orbit scattering, Jz∝t0.5. We
illustrate how this conundrum can be resolved if we also account for
the fact that at earlier epochs, the scatterers were more common, and
the restoring force from the stellar disk surface mass density was
low. Our analysis may reinstate gradual orbital scattering as a
plausible and viable mechanism to explain the age-dependent vertical
motions of disk stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 163 20764 APOGEE red clump value-added catalog
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See also:
V/117 : Geneva-Copenhagen Survey of Solar neighbourhood (Holmberg+, 2007)
V/130 : Geneva-Copenhagen Survey of Solar neighbourhood III (Holmberg+, 2009)
III/284 : APOGEE-2 data from DR16 (Johnsson+, 2020)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
J/A+A/480/91 : Gal. disk stars vertical distribution. IV. (Soubiran+, 2008)
J/ApJ/706/1364 : SINS survey of high-redshift gal. (Forster Schreiber+, 2009)
J/A+A/530/A138 : Geneva-Copenhagen survey re-analysis (Casagrande+, 2011)
J/MNRAS/419/1637 : Nearby red clump stars JHK observations (Laney+, 2012)
J/MNRAS/421/3362 : Kinematics of galactic red clump stars (Bilir+, 2012)
J/MNRAS/456/3655 : Masses and ages of red giants (Martig+, 2016)
J/A+A/588/A87 : Seismic global parameters of 6111 KIC (Vrard+, 2016)
J/ApJ/823/114 : The Cannon: a new approach to determine masses (Ness+, 2016)
J/ApJ/858/L7 : Red clump stars selected from LAMOST and APOGEE (Ting+, 2018)
J/ApJS/239/32 : APOKASC-2 cat. of Kepler evolved stars (Pinsonneault+, 2018)
J/ApJ/872/95 : GALEX & Gaia data for APOGEE red clump stars (Mohammed+, 2019)
J/ApJ/872/137 : Abund. of red clump & RGB stars with APOGEE (Shetrone+, 2019)
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 identifier
(from Ting+, 2018, J/ApJ/858/L7)
20- 25 F6.3 [-] [Fe/H] [-0.7/0.4] Abundance, [Fe/H] (1)
27- 32 F6.3 [-] [Mg/Fe] [-0.15/0.3] Abundance, [Mg/Fe] (1)
34- 52 I19 --- Gaia Gaia DR2 (I/345) source identifier
54- 62 F9.5 deg RAdeg Gaia DR2 Right Ascension (ICRS) at Ep=2015.5
64- 72 F9.5 deg DEdeg Gaia DR2 Declination (ICRS) at Ep=2015.5
74- 80 F7.5 Gyr Age [0.16/8] Stellar age (2)
82- 88 F7.5 kpc Dist [0.026/8.8] Inferred photometric red clump
distance from the Sun
90- 97 F8.5 kpc Rgc [3/16.4] Galactocentric observed radius
99-106 F8.5 kpc Zgc [-0.5/0.5] Galactic observed height
108-118 F11.5 kpc RgcBirth [0.00095/17.4]?=-9999 Inferred birth radius
120-130 F11.5 kpc RgcMean [1.8/14.7]?=-9999 Mean Radius (3)
132-142 F11.5 kpc.km/s JR [0/1492]?=-9999 Radial phase space action
144-153 F10.5 kpc.km/s Lz [-125/6580] Angular momentum
phase space action
155-163 F9.5 kpc.km/s Jz [9e-5/1000] Vertical phase space action
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Note (1): Abundances derived from The Payne method (Ting+ 2019ApJ...879...69T 2019ApJ...879...69T).
Note (2): Stellar ages inferred from the spectra via an asteroseismic
training set.
Note (3): Mean radii are defined to be the average of the observed radii
and the birth radii.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Nov-2020