Dissemin is shutting down on January 1st, 2025

Published in

American Astronomical Society, Astrophysical Journal, 1(937), p. 20, 2022

DOI: 10.3847/1538-4357/ac86c7

Links

Tools

Export citation

Search in Google Scholar

On the Robustness of the Velocity Anisotropy Parameter in Probing the Stellar Kinematics in Milky Way–Like Galaxies: Takeaway from TNG50 Simulation

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

Full text: Download

Red circle
Preprint: archiving forbidden
Red circle
Postprint: archiving forbidden
Green circle
Published version: archiving allowed
Data provided by SHERPA/RoMEO

Abstract

Abstract We analyze the velocity anisotropy of stars in real and energy space for a sample of Milky Way–like galaxies in the TNG50 simulation. We employ different selection criteria, including spatial, kinematic, and metallicity cuts, and make three halo classes (  –  ) that show mild-to-strong sensitivity to different selections. The above classes cover 48%, 16%, and 36% of the halos, respectively. We analyze the β radial profiles and divide them into either monotonically increasing radial profiles or ones with peaks and troughs. We demonstrate that halos with monotonically increasing β profiles are mostly from class  , while those with peaks/troughs are part of classes  and  . This means that care must be taken, as the observationally reported peaks/troughs might be a consequence of different selection criteria. We infer the anisotropy parameter β energy space and compare that against the β radial profile. It is seen than 65% of halos with very mild sensitivity to different selections in real space are those for which the β radial and energy profiles are closely related. Consequently, we propose that comparing the β radial and energy profiles might be a novel way to examine the sensitivity to different selection criteria and thus examining the robustness of the anisotropy parameter in tracing stellar kinematics. We compare simulated β radial profiles against various observations and demonstrate that, in most cases, the model diversity is comparable with the error bars from different observations, meaning that the TNG50 models are in good overall agreement with observations.