The many reasons that the rotation curves of low-mass galaxies can fail as tracers of their matter distributions

Downing, Eleanor R; Oman, Kyle A

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<vmax/kms−1<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.

Citation

Downing, E. R., & Oman, K. A. (2023). The many reasons that the rotation curves of low-mass galaxies can fail as tracers of their matter distributions. Monthly Notices of the Royal Astronomical Society, 522(3), 3318-3336. https://doi.org/10.1093/mnras/stad868

• Journal Article Type: Article
• Acceptance Date: Mar 17, 2023
• Online Publication Date: Mar 23, 2023
• Publication Date: 2023-07
• Deposit Date: Aug 17, 2023
• Publicly Available Date: Aug 17, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 522
• Issue: 3
• Pages: 3318-3336
• DOI: https://doi.org/10.1093/mnras/stad868
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://durham-repository.worktribe.com/output/1720325