Cosmological simulations with self-interacting dark matter – II. Halo shapes versus observations

By A. Peter, Miguel Rocha, James S. Bullock, M. Kaplinghat. 2012

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If dark matter has a large self-interaction scattering cross section, then interactions among dark-matter particles will drive galaxy and cluster halos to become spherical in their centers. Work in the past has used this effect to rule out velocity-independent, elastic cross sections larger than sigma/m ~ 0.02 cm^2/g based on comparisons to the shapes of galaxy cluster lensing potentials and X-ray isophotes. In this paper, we use cosmological simulations to show that these constraints were off by more than an order of magnitude because (a) they did not properly account for the fact that the observed ellipticity gets contributions from the triaxial mass distribution outside the core set by scatterings, (b) the scatter in axis ratios is large and (c) the core region retains more of its triaxial nature than estimated before. Including these effects properly shows that the same observations now allow dark matter self-interaction cross sections at least as large as sigma/m = 0.1 cm^2/g. We show that constraints on self-interacting dark matter from strong-lensing clusters are likely to improve significantly in the near future, but possibly more via central densities and core sizes than halo shapes.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/bfc9b006b03af55bd1a00822b9e58700dee470a5

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Citations in the corpus

Core formation in dwarf haloes with self-interacting dark matter: no fine-tuning necessary (2014, background): “1 cm2 g−1) come from galaxy clusters with characteristic rms velocities vrms ' 1000 km s−1 (Yoshida et al., 2000; Gnedin & Ostriker, 2001; Randall et al., 2008; Rocha et al., 2013; Peter et al., 2013).”
THE SHAPE OF THE INNER MILKY WAY HALO FROM OBSERVATIONS OF THE PAL 5 AND GD–1 STELLAR STREAMS (2016, background): “…especially interesting prediction, as, e.g., non-canonical dark–matter models such as self-interacting dark matter predict that halos should be spherical in their high-density inner regions (Spergel & Steinhardt 2000; Yoshida et al. 2000; Davé et al. 2001; Miralda-Escudé 2002; Peter et al. 2013).”
The Dark Photon (2020, background): “On the other hand, results on galaxies from N -body simulations in self-interacting dark matter cosmologies (Peter et al., 2013), which take into account predicted ellipticities and dark matter densities in the central regions, seem to go in the direction of milder constraints, about at the same…”
WHY BARYONS MATTER: THE KINEMATICS OF DWARF SPHEROIDAL SATELLITES (2012, background): “Tension currently exists over the necessary cross-section for DM interaction that can yield core sizes as observed in dwarfs compared to halo shapes of galaxy clusters (Peter et al. 2013; Rocha et al. 2013; Zavala et al. 2013).”
Small scale problems of the $\Lambda$CDM model: a short review (2016, background): “alo mass ranging from galaxies to clusters and two values of s/m. As the cored SIDM subhaloes feel more tidal stripping and disruption than CDM subhaloes, it solves the CC problem and improves on WDM [344,345] since it leaves enough subhaloes (see however [334] for a different point of view). Note a”
The impact of baryonic physics on the structure of dark matter haloes: the view from the FIRE cosmological simulations (2015, background): “However, recent SIDM models that take into account more accurate observational constraints and the effects of baryons offer promising explanation of the problem without violating any known observational constraints (Rocha et al. 2013; Peter et al. 2013; Kaplinghat et al. 2014; Elbert et al. 2015).”