J/A+A/619/A72 Milky Way disk kinematic sub-structures (Ramos+, 2018)
Riding the kinematic waves in the Milky Way disk with Gaia.
Ramos P., Antoja T., Figueras F.
<Astron. Astrophys. 619, A72 (2018)>
=2018A&A...619A..72R 2018A&A...619A..72R (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, nearby ; Space velocities
Keywords: Galaxy: kinematics and dynamics - Galaxy: disk - Galaxy: structure -
solar neighbourhood
Abstract:
Gaia DR2 has delivered full-sky six-dimensional measurements for
millions of stars, and the quest to understand the dynamics of our
Galaxy has entered a new phase.
Our aim is to reveal and characterise the kinematic substructure of
the different Galactic neighbourhoods, to form a picture of their
spatial evolution that can be used to infer the Galactic potential,
its evolution, and its components.
We take approximately 5 million stars in the Galactic disk from the
Gaia DR2 catalogue and build the velocity distribution in different
Galactic neighbourhoods distributed along 5kpc in Galactic radius and
azimuth. We decompose their distribution of stars in the VR-Vφ
plane with the wavelet transformation and asses the statistical
significance of the structures found.
We detect distinct kinematic substructures (arches and more rounded
groups) that diminish their azimuthal velocity as a function of
Galactic radius in a continuous way, connecting volumes up to 3kpc
apart in some cases. The average rate of decrease is ∼23km/s/kpc. In
azimuth, the variations are much smaller. We also observe different
behaviours: some approximately conserve their vertical angular
momentum with radius (e.g. Hercules), while others seem to have nearly
constant kinetic energy (e.g. Sirius). These two trends are consistent
with the approximate predictions of resonances and phase mixing,
respectively. Besides, the overall spatial evolution of Hercules is
consistent with being related to the outer Lindblad resonance of the
Galactic bar. In addition, we detect new kinematic structures that
only appear at either inner or outer Galactic radius, different from
the solar neighbourhood.
The strong and distinct variation observed for each kinematic
substructure with position in the Galaxy, along with the
characterisation of extrasolar moving groups, will allow to better
model the dynamical processes affecting the velocity distributions.
Description:
Position of the peaks detected in the velocity plane with the Wavelet
Transformation, at the scale j=3 (4-8km/s). It contains only those
overdensities significant according to at least one of the two
indicators (Poisson noise or Bootstrap).
The table contains also the common name given to the structure (if
any), the value of the wavelet coefficient, the number of stars
contributing to the peak, as well as their median uncertainty in the
velocity components. Finally, it shows the number of structures in the
selected literature that fall inside the circle of 8km/s defined
around the over-density ('Matches').
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 69 195 All the significant peaks in the Solar
Neighbourhood sample at the scale 4-8km/s (j=3)
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/195] According to wavelet coefficient
5- 23 A19 --- Name Name in the literature that is most commonly
assigned to the group (1)
25- 30 F6.1 km/s Vr Velocity in the GC->Sun direction,
positive outwards
32- 37 F6.1 km/s Vphi Azimuthal velocity, negative in the direction
of the Galactic rotation
39- 45 F7.4 --- Wavelet Coefficient of the wavelet transformation
47 I1 --- CL [0-3] Poisson significance
49- 52 F4.2 --- PBS Bootstrap probability of observing the peak
54- 57 I4 --- Stars Number of stars inside a circle of radius
8km/s centred at the peak
59- 62 F4.1 km/s sigmaVrM Median uncertainty in Vr
64- 67 F4.1 km/s sigmaVphiM Median uncertainty in Vphi
69 I1 --- Matches [0/2] Unique Moving Groups close to the peak
in the selected literature
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Note (1): Appendix C of the article contains an extended explanation of this
field.
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Antoja12 (15) = 2012MNRAS.426L...1A 2012MNRAS.426L...1A, [AHB2012] 15 in Simbad
Bobylev16 (14) = 2016AstL...42...90B 2016AstL...42...90B, [BB2016] 14 in Simbad
Bobylev16 (15) = 2016AstL...42...90B 2016AstL...42...90B, [BB2016] 15 in Simbad
Coma Berenices = NAME Coma Berenices Moving Group in Simbad
Dehnen 98 (11) = 1998AJ....115.2384D 1998AJ....115.2384D, [D98b] 11 in Simbad
Dehnen 98 (14) = 1998AJ....115.2384D 1998AJ....115.2384D, [D98b] 14 in Simbad
Dehnen 98 (6) = 1998AJ....115.2384D 1998AJ....115.2384D, [D98b] 6 in Simbad
Hercules II = Hercules II Moving Group
Hyades = NAME Hyades Moving Group in Simbad
Kushniruk17 (J3-13) = 2017A&A...608A..73K 2017A&A...608A..73K, group 13
Kushniruk17 (J3-18) = 2017A&A...608A..73K 2017A&A...608A..73K, group 18
Kushniruk17 (J3-19) = 2017A&A...608A..73K 2017A&A...608A..73K, group 19
Pleiades = NAME Pleiades Moving Group in Simbad
Sirius = NAME Sirius Moving Group
eps Ind = epsilon Ind Moving Group
gammaLeo = gamma Leo Moving Group
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Acknowledgements:
Pau Ramos, pramos(at)fqa.ub.edu
(End) Patricia Vannier [CDS] 20-Aug-2018