Affiliation:
1. Institute for Computational Cosmology, Durham University , South Road, Durham DH1 3LE, UK
2. Department of Physics, Durham University , South Road, Durham DH1 3LE, UK
Abstract
ABSTRACT
It is routinely assumed that galaxy rotation curves are equal to their circular velocity curves (modulo some corrections) such that they are good dynamical mass tracers. We take a visualization-driven approach to exploring the limits of the validity of this assumption for a sample of 33 low-mass galaxies ($60\lt v_\mathrm{max}/\mathrm{km}\, \mathrm{s}^{-1}\lt 120$ ) from the APOSTLE suite of cosmological hydrodynamical simulations. Only three of these have rotation curves nearly equal to their circular velocity curves at z = 0, the rest are undergoing a wide variety of dynamical perturbations. We use our visualizations to guide an assessment of how many galaxies are likely to be strongly perturbed by processes in several categories: mergers/interactions (affecting 6/33 galaxies), bulk radial gas inflows (19/33), vertical gas outflows (15/33), distortions driven by a non-spherical DM halo (17/33), warps (8/33), and winds due to motion through the intergalactic medium (5/33). Most galaxies fall into more than one of these categories; only 5/33 are not in any of them. The sum of these effects leads to an underestimation of the low-velocity slope of the baryonic Tully–Fisher relation (α ∼ 3.1 instead of α ∼ 3.9, where Mbar ∝ vα) that is difficult to avoid, and could plausibly be the source of a significant portion of the observed diversity in low-mass galaxy rotation curve shapes.
Funder
European Research Council
STFC
Publisher
Oxford University Press (OUP)
Subject
Space and Planetary Science,Astronomy and Astrophysics
Cited by
2 articles.
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