Dark matter cores and cusps: the case of multiple stellar populations in dwarf spheroidals

By Nicola C. Amorisco, N. Evans II. 2011

174 citations recorded by the source corpus.

A number of dwarf spheroidal (dSph) galaxies are known to contain a more extended, metal-poor population with a flattish velocity dispersion profile, and a more concentrated, metal-rich population with a velocity dispersion declining with radius. The two populations can be modelled with Michie–King distribution functions (DFs) in the isothermal and in the sharply truncated limits, respectively. We argue that the truncation of the metal-rich population can be traced back to the spatial distribution of the star-forming gas. Suppose δ is the exponent of the first non-constant term in the Taylor expansion of the total potential at the centre (δ= 1 for Navarro–Frenk–White or NFW haloes, δ= 2 for cored haloes). Then, we show that the ratio of the half-light radii of the populations Rδ/2h, 2/Rh, 1δ/2 must be smaller than the ratio of the line-of-sight velocity dispersions σlos, 2(Rh, 2)/σlos, 1(Rh, 1). Specializing to the case of the Sculptor dSph, we develop a technique to fit simultaneously both populations with Michie–King DFs. This enables us to determine the mass profile of the Sculptor dSph with unprecedented accuracy in the radial range 0.2 < r < 1.2 kpc. We show that cored halo models are preferred over cusped halo models, with a likelihood ratio test rejecting NFW models at any significance level higher than 0.05 per cent. Even more worryingly, the best-fitting NFW models require concentrations with c ≲ 20, which is not in the cosmologically preferred range for dwarf galaxies. We conclude that the kinematics of multiple populations in dSphs provides a substantial new challenge for theories of galaxy formation, with the weight of available evidence strongly against dark matter cusps at the centre.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/49066260dc4594748461ae92461e940c246fa8f2

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Citations in the corpus

A White Paper on keV sterile neutrino Dark Matter (2016, methodology): “[599] used full phase space distribution functions to model the multiple populations in Sculptor and demonstrated that cored halo models are very strongly preferred over cusped ones.”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, methodology): “10, the acquisition of further line-of-sight velocities will enable the DM density to be mapped out using the methods of Walker & Peñarrubia (2011) and Amorisco & Evans (2012).”
Constraining self-interacting dark matter with the Milky Way’s dwarf spheroidals (2012, background): “It is now clear that observations of dark matter dominated systems such as low-mass (dwarf) and low surface brightness (LSB) galaxies favour the presence of dark matter cores ofO(1 kpc) (e.g. Moore 1994, Kuzio de Naray et al. 2008, de Blok 2010, Walker & Peñarrubia 2011, Amorisco & Evans 2012).”
Cores in warm dark matter haloes: a Catch 22 problem (2012, background): “This is not sufficient to explain the observed cores in dwarf galaxies that are around kpc scale (Walker & Penarrubia 2011; Amorisco & Evans 2012; Jardel & Gebhard 2012).”
Cusp-core transformations in dwarf galaxies: observational predictions (2012, background): “It is interesting to note, however, that the very latest dynamical models for Sculptor appear to favour a cored rather than cusped mass distribution (Battaglia et al. 2008; Walker & Peñarrubia 2011; Amorisco & Evans 2012).”
Too big to fail in the Local Group (2014, methodology): “…measurements of stellar kinematics in dSphs, utilizing both kinematically distinct populations (Walker & Peñarrubia 2011; Agnello & Evans 2012; Amorisco & Evans 2012; Amorisco, Agnello & Evans 2013) and treating the system as a single population (Jardel & Gebhardt 2012) indicate cored matter…”
A KINEMATIC STUDY OF THE ANDROMEDA DWARF SPHEROIDAL SYSTEM (2013, background): “From studies of brighter dSphs, such as Sculptor and Fornax (Walker & Peñarrubia 2011; Amorisco & Evans 2012; Jardel & Gebhardt 2012) it appears that their halo density profiles are also inconsistent with hosting central cusps.”
THE COUPLING BETWEEN THE CORE/CUSP AND MISSING SATELLITE PROBLEMS (2012, background): “…significantly: the estimated mass profiles are consistent with homogeneous-density ’cores’ (Kuzio de Naray et al. 2008; Battaglia et al. 2008; de Blok 2010; Walker & Peñarrubia 2011; Amorisco & Evans 2012) and the satellite mass function is remarkably flat (Klypin et al. 1999; Moore et al. 1999).”
Can feedback solve the too-big-to-fail problem? (2013, result): “The authors thank Manoj Kaplinghat for insightful discussions, and also thank Alyson Brooks, Arianna di Cintio, Avishai Dekel, Anatoly Klypin, Andrea Maccio, Jorge Peñarrubia, Andrew Pontzen, Antonio Del Popolo, Chris Purcell, Justin Read, Romain Teyssier, Erik Tollerud, Matthew Walker, and particu”
WHY BARYONS MATTER: THE KINEMATICS OF DWARF SPHEROIDAL SATELLITES (2012, methodology): “Studies using this method (Walker & Peñarrubia 2011; Amorisco & Evans 2012; Battaglia et al. 2008; Agnello & Evans 2012) conclude that both Fornax (with slope measured out to ∼1 kpc) and Sculptor (measured interior to 500 pc) favor cored density profiles, and exclude cuspy density profiles at high…”
Bar formation and evolution in disc galaxies with gas and a triaxial halo: morphology, bar strength and halo properties (2012, background): “…de Blok et al. 2001, 2008; de Blok & Bosma 2002; de Blok, Bosma & McGaugh 2003; Simon et al. 2003; Kuzio de Naray et al. 2006; Battaglia et al. 2008; Kuzio de Naray, McGaugh & de Blok 2008; Oh et al. 2008; de Blok 2010; Walker & Peñarrubia 2011; Amorisco & Evans 2012; Peñarrubia et al. 2012).”
Cosmological Simulations with Self-Interacting Dark Matter I: Constant Density Cores and Substructure (2012, methodology): “…modelings using stellar kinematics together with chemo-dynamiclly distinct stellar subcomponets of Milky Way dwarf spheroidal gaaxies suggest central densities of approximately∼ 0.1M⊙/pc3 (Strigari et al. 2008; Wolf et al. 2010; Walker & Peñarrubia2011; Amorisco & Evans 2012; Wolf & Bullock 2012).”