The relationship between the morphology and kinematics of galaxies and its dependence on dark matter halo structure in EAGLE

Thob, ACR, Crain, RA, McCarthy, IG, Schaller, M, Lagos, CDP, Schaye, J, Talens, GJJ, James, PA, Theuns, T and Bower, RG The relationship between the morphology and kinematics of galaxies and its dependence on dark matter halo structure in EAGLE. Monthly Notices of the Royal Astronomical Society. ISSN 0035-8711 (Accepted)

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Abstract

We investigate the connection between the morphology and internal kinematics of the stellar component of central galaxies with mass $M_\star > {10}^{9.5} {\rm M}_\odot$ in the EAGLE simulations. We compare several kinematic diagnostics commonly used to describe simulated galaxies, and find good consistency between them. We model the structure of galaxies as ellipsoids and quantify their morphology via the ratios of their principal axes, finding that kinematic diagnostics enable a superior differentiation of blue star-forming and red quiescent galaxies than morphological definitions. Flattened oblate galaxies exhibit greater rotational support than their spheroidal counterparts, but there is significant scatter in the relationship between morphological and kinematical diagnostics, such that kinematically-similar galaxies can exhibit a broad range of morphologies. The scatter in the relationship between the flattening and the ratio of the rotation and dispersion velocities ($v/\sigma$) correlates strongly with the anisotropy of the stellar velocity dispersion: at fixed $v/\sigma$, flatter galaxies exhibit greater dispersion in the plane defined by the intermediate and major axes than along the minor axis, indicating that the morphology of simulated galaxies is influenced significantly by the structure of their velocity dispersion. The simulations reveal that this anisotropy correlates with the intrinsic morphology of the galaxy's inner dark matter halo, i.e. the halo's morphology that emerges in the absence of dissipative baryonic physics. This implies the existence of a causal relationship between the morphologies of galaxies and that of their host dark matter haloes.

Item Type: Article This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Adrien C R Thob, Robert A Crain, Ian G McCarthy, Matthieu Schaller, Claudia D P Lagos, Joop Schaye, Geert Jan J Talens, Philip A James, Tom Theuns, Richard G Bower; The relationship between the morphology and kinematics of galaxies and its dependence on dark matter halo structure in EAGLE, Monthly Notices of the Royal Astronomical Society, , stz448 is available online at: https://dx.doi.org/10.1093/mnras/stz448 astro-ph.GA; astro-ph.GA Q Science > QB AstronomyQ Science > QC Physics Astrophysics Research Institute Oxford University Press Author 20 Feb 2019 10:44 20 Feb 2019 10:49 http://researchonline.ljmu.ac.uk/id/eprint/10188

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