J/A+A/618/A121 Azimuthal anisotropy of stellar galactic disks (Chemin, 2018)
A mass-velocity anisotropy relation in galactic stellar disks.
Chemin L.
<Astron. Astrophys. 618, A121 (2018)>
=2018A&A...618A.121C 2018A&A...618A.121C (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galaxy catalogs ; Morphology
Keywords: galaxies: kinematics and dynamics - galaxies: fundamental parameters -
galaxies: stellar content - galaxies: individual: Milky Way
Abstract:
The ellipsoid of stellar random motions is a fundamental ingredient of
galaxy dynamics. Yet it has long been difficult to constrain this
component in disks others than the Milky Way. This article presents
the modeling of the azimuthal-to-radial axis ratio of the velocity
ellipsoid of galactic disks from stellar dispersion maps using
integral field spectroscopy data of the CALIFA survey. The measured
azimuthal anisotropy is shown to be not strongly dependent on the
assumed vertical-to-radial dispersion ratio of the ellipsoid. The
anisotropy distribution shows a large diversity in the orbital
structure of disk galaxies from tangential to radial stellar orbits.
Globally, the orbits are isotropic in inner disk regions and become
more radial as a function of radius, although this picture tends to
depend on galaxy morphology and luminosity. The Milky Way orbital
anisotropy profile measured from the Second Gaia Data Release is
consistent with those of CALIFA galaxies. A new correlation is
evidenced, linking the absolute magnitude or stellar mass of the disks
to the azimuthal anisotropy. More luminous disks have more radial
orbits and less luminous disks have isotropic and somewhat tangential
orbits. This correlation is consistent with the picture in galaxy
evolution in which orbits become more radial as the mass grows and is
redistributed as a function of time. With the help of circular
velocity curves, it is also shown that the epicycle theory fails to
reproduce the diversity of the azimuthal anisotropy of stellar random
motions, as it predicts only nearly radial orbits in the presence of
flat curves. The origin of this conflict is yet to be identified. It
also questions the validity of the vertical-to-radial axis ratio of
the velocity ellipsoid derived by many studies in the framework of the
epicyclic approximation.
Description:
Azimuthal anistropy of 93 disk galaxies from the CALIFA sample. Values
represent the median of the anisotropy profile and interpolations at
R=0.5h, h, 2h, Re, where h is the stellar disk scale-length and Re the
galaxy effective radius. Photometric radii are given in CALIFA papers
Falcon-Barroso et al. (2017, Cat. J/A+A/597/A48) and Mendez-Abreu et
al. (2017, J/A+A/598/A32). For each galaxy, the quoted error
associated to the median anisotropy is the median of the errors of the
anistropy profile.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 71 93 Disk galaxies from the CALIFA sample
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See also:
J/A+A/597/A48 : Stellar kinematics in CALIFA survey (Falcon-Barroso+, 2017)
J/A+A/598/A32 : 2D decomposition of CALIFA galaxies (Mendez-Abreu+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Galaxy Galaxy name
15- 16 I2 --- Nbin Number of radial bins in anisotropy profile
18- 22 F5.2 --- B05h ?=- Azimuthal anisotropy (at R=h/2)
24- 27 F4.2 --- e_B05h ?=- Error on azimuthal anisotropy (at R=h/2)
29- 33 F5.2 --- B1h ?=- Azimuthal anisotropy at R=h
35- 38 F4.2 --- e_B1h ?=- Error on azimuthal anisotropy at R=h
40- 44 F5.2 --- B2h ?=- Azimuthal anisotropy at R=2h
46- 49 F4.2 --- e_B2h ?=- Error on azimuthal anisotropy at R=2h
51- 55 F5.2 --- Bre ?=- Azimuthal anisotropy at R=Re
57- 60 F4.2 --- e_Bre ?=- Error on azimuthal anisotropy at R=Re
62- 66 F5.2 --- Bmed Median azimuthal anisotropy from profile
68- 71 F4.2 --- e_Bmed Error on median azimuthal anisotropy
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Acknowledgements:
Laurent Chemin, astro.chemin(at)gmail.com
(End) Laurent Chemin [Univ. Antofagasta], Patricia Vannier [CDS] 03-Aug-2018