Revisiting the Stellar Velocity Ellipsoid - Hubble type relation: observations versus simulations

Abstract

The stellar velocity ellipsoid (SVE) in galaxies can provide important information on the processes that participate in the dynamical heating of their disc components (e.g. giant molecular clouds, mergers, spiral density waves, bars). Earlier findings suggested a strong relation between the shape of the disc SVE and Hubble type, with later-type galaxies displaying more anisotropic ellipsoids and early-types being more isotropic. In this paper, we revisit the strength of this relation using an exhaustive compilation of observational results from the literature on this issue. We find no clear correlation between the shape of the disc SVE and morphological type, and show that galaxies with the same Hubble type display a wide range of vertical-to-radial velocity dispersion ratios. The points are distributed around a mean value and scatter of ${\sigma }_z/{\sigma }_R=0.7\pm 0.2$. With the aid of numerical simulations, we argue that different mechanisms might influence the shape of the SVE in the same manner and that the same process (e.g. mergers) does not have the same impact in all the galaxies. The complexity of the observational picture is confirmed by these simulations, which suggest that the vertical-to-radial axis ratio of the SVE is not a good indicator of the main source of disc heating. Our analysis of those simulations also indicates that the observed shape of the disc SVE may be affected by several processes simultaneously and that the signatures of some of them (e.g. mergers) fade over time.

Published in MNRAS, 05 January 2018. 17 pages, 9 figures, 4 tables

References in corpus (21)

• The Radial Velocity Experiment (RAVE): first data release
• New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey
• The KMOS^3D Survey: design, first results, and the evolution of galaxy kinematics from 0.7<z<2.7
• The SAURON project -- X. The orbital anisotropy of elliptical and lenticular galaxies: revisiting the (V/sigma,epsilon) diagram with integral-field stellar kinematics
• The long bar as seen by the VVV survey: I. Colour-magnitude diagrams
• Vertical disc heating in Milky Way-sized galaxies in a cosmological context
• Light and Motion in SDSS Stripe 82: The Catalogues
• Cold Dark Matter Substructure and Galactic Disks II: Dynamical Effects of Hierarchical Satellite Accretion
• Age velocity dispersion relations and heating histories in disc galaxies
• The effect of radial migration on galactic disks
• Dissecting simulated disc galaxies II: the age-velocity relation
• Galaxies grow their bulges and black holes in diverse ways
• A numerical study of interactions and stellar bars
• Kinematic clues to bar evolution for galaxies in the local universe: why the fastest rotating bars are rotating most slowly
• A unified model for age-velocity dispersion relations in Local Group galaxies: Disentangling ISM turbulence and latent dynamical heating
• Line-of-sight velocity dispersions and a mass distribution model of the Sa galaxy NGC 4594
• The BaLROG project - II. Quantifying the influence of bars on the stellar populations of nearby galaxies
• Exploring Disk Galaxy Dynamics Using IFU Data
• Disk mass and disk heating in the spiral galaxy NGC 3223
• The imprints of bars on the vertical stellar population gradients of galactic bulges
• Stellar kinematics using a third integral of motion: method and application on the Andromeda galaxy

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• Resolved stellar population properties of PHANGS-MUSE galaxies
• From giant clumps to clouds I: the impact of gas fraction evolution on the stability of galactic discs
• Angular momentum and local gravitational instability in galaxy discs: does $Q$ correlate with $j$ or $M$?
• Bars and boxy/peanut bulges in thin and thick discs. II. Can bars form in hot thick discs?
• Gravitational instability and star formation in NGC 628
• How the bar properties affect the induced spiral structure
• Quantifying the influence of bars on action-based dynamical modelling of disc galaxies
• NGC 7457: Evidence for merger-driven cylindrical rotation in disc galaxies
• A mass-velocity anisotropy relation in galactic stellar disks
• Local variations of the Stellar Velocity Ellipsoid-I: the disc of galaxies in the Auriga simulations
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