The shape of dark matter haloes in the Aquarius simulations: evolution and memory

By C. Vera-Ciro, L. Sales, A. Helmi, Carlos S. Frenk, J. Navarro, Volker Springel, M. Vogelsberger, Simon D. M. White. 2011

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We use the high resolution cosmological N-body simulations from the Aquarius project to investigate in detail the mechanisms that determine the shape of Milky Way-type dark matter haloes. We find that, when measured at the instantaneous virial radius, the shape of individual haloes changes with time, evolving from a typically prolate configuration at early stages to a more triaxial/oblate geometry at the present day. This evolution in halo shape correlates well with the distribution of the infalling material: prolate configurations arise when haloes are fed through narrow filaments, which characterizes the early epochs of halo assembly, whereas triaxial/oblate configurations result as the accretion turns more isotropic at later times. Interestingly, at redshift z = 0, clear imprints of the past history of each halo are recorded in their shapes at different radii, which also exhibit a variation from prolate in the inner regions to triaxial/oblate in the outskirts. Provided that the Aquarius haloes are fair representatives of Milky Way-like 1012Msun objects, we conclude that the shape of such dark matter haloes is a complex, time-dependent property, with each radial shell retaining memory of the conditions at the time of collapse.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5d1fd5efeb9cc149061c1db060615a7f14cb8a72

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Citations in the corpus

Structure finding in cosmological simulations: the state of affairs (2013, background): “…all the particles within a spherical volume or shell, but the initial surface is deformed along the principal axes of the best-fitting ellipsoid, and the process is repeated until convergence is reached (e.g. Dubinski & Carlberg 1991; Warren et al. 1992; Allgood et al. 2006; Vera-Ciro et al. 2011).”
Cosmological simulations with self-interacting dark matter – II. Halo shapes versus observations (2012, result): “Shape estimates, especially integral estimates, are most reliable if there are at least ∼ 104 particles within the virial radius (or tidal radius for subhalos), consistent to what has been found in earlier work (e.g., Allgood et al. 2006; Vera-Ciro et al. 2011). c© 0000 RAS, MNRAS 000, 000–000”
Bar formation and evolution in disc galaxies with gas and a triaxial halo: morphology, bar strength and halo properties (2012, background): “Yet cosmological simulations (e.g. Dubinski & Carlberg 1991; Jing & Suto 2002; Bailin & Steinmetz 2005; Allgood et al. 2006; Novak et al. 2006; Vera-Ciro et al. 2011; Schneider, Frenk & Cole 2012) have shown that in cases with no baryons the haloes are strongly triaxial, as could be expected by the…”
THE SHAPE OF THE INNER MILKY WAY HALO FROM OBSERVATIONS OF THE PAL 5 AND GD–1 STELLAR STREAMS (2016, background): “In the absence of baryons, dark–matter halos are generally found to be strongly triaxial (e.g., Frenk et al. 1988; Dubinski & Carlberg 1991; Warren et al. 1992; Cole & Lacey 1996; Jing & Suto 2002; Vera-Ciro et al. 2011).”
The DiskMass Survey VII. The distribution of luminous and dark matter in spiral galaxies (2013, background): “There have been studies showing that the dark-matter halo might be highly oblate or prolate (e.g., Amorisco & Bertin 2010; Vera-Ciro et al. 2011).”
Idealized models for galactic disc formation and evolution in ‘realistic’ ΛCDM haloes (2012, background): “The orientations of the halo principal axes and the halo spin axis can change with time (see Vera-Ciro et al. 2011 and Bett & Frenk 2012, respectively) and so apparently, can the preferred disc orientation, as is clear from the halo A run of CS09, where a disc is destroyed by inflowing matter…”
Dwarf galaxy planes: the discovery of symmetric structures in the Local Group (2013, background): “…accretion scenario is that cosmological dark matter filaments are more extended than the virial radius of the host galaxy dark matter halo (Vera-Ciro et al. 2011), such that they are orders of magnitude too wide to be responsible for the formation of a structure only a few 10 kpc thin, a…”
The Dark Matter Crisis: Falsification of the Current Standard Model of Cosmology (2012, background): “Beyond this distance the shape is likely to be more oblate (Bullock 2002; Ruzicka et al. 2007), and invoking continuity shows that the axis ratio qd cannot change drastically (e.g. Vera-Ciro et al. 2011).”
Tracing the dark matter sheet in phase space (2011, methodology): “This is the same decomposition that can be made in the GDE approach of Vogelsberger et al. (2008) as shown for the environment of Aquarius haloes in Vera-Ciro et al. (2011) (their Figure B1) and Vogelsberger & White (2011) (their Figure 4).”