Dark Matter Substructure in Numerical Simulations: A Tale of Discreteness Noise, Runaway Instabilities, and Artificial Disruption

By F. V. D. Bosch, Go Ogiya. 2018

178 citations recorded by the source corpus.

To gain understanding of the complicated, non-linear, and numerical processes associated with the tidal evolution of dark matter subhaloes in numerical simulation, we perform a large suite of idealized simulations that follow individual N-body subhaloes in a fixed, analytical host halo potential. By varying both physical and numerical parameters, we investigate under what conditions the subhaloes undergo disruption. We confirm the conclusions from our more analytical assessment in van den Bosch et al. that most disruption is numerical in origin; as long as a subhalo is resolved with sufficient mass and force resolution, a bound remnant survives. This implies that state-of-the-art cosmological simulations still suffer from significant overmerging. We demonstrate that this is mainly due to inadequate force softening, which causes excessive mass loss and artificial tidal disruption. In addition, we show that subhaloes in N-body simulations are susceptible to a runaway instability triggered by the amplification of discreteness noise in the presence of a tidal field. These two processes conspire to put serious limitations on the reliability of dark matter substructure in state-of-the-art cosmological simulations. We present two criteria that can be used to assess whether individual subhaloes in cosmological simulations are reliable or not, and advocate that subhaloes that satisfy either of these two criteria be discarded from further analysis. We discuss the potential implications of this work for several areas in astrophysics.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/ac756d0b74efabeed3156f82bc2da02d0065313c

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Citations in the corpus

The Local Group on FIRE: dwarf galaxy populations across a suite of hydrodynamic simulations (2018, background): “6 may be (spuriously) destroyed due to finite mass resolution (van den Bosch & Ogiya 2018).”
Milky Way Satellite Census. II. Galaxy–Halo Connection Constraints Including the Impact of the Large Magellanic Cloud (2019, background): “Although we have not explicitly considered artificial subhalo disruption in this list of theoretical uncertainties (e.g., van den Bosch et al. 2018; van den Bosch & Ogiya 2018), our fiducial orphan satellite model effectively assumes that subhalo disruption in dark matter– only simulations is…”
Hunting for the Dark Matter Wake Induced by the Large Magellanic Cloud (2019, methodology): “In general the number of particles used in our simulations is 6 orders of magnitude greater than the regimes where these effects take place, as discussed in van den Bosch et al. (2018); van den Bosch & Ogiya (2018).”