A UNIVERSAL MASS PROFILE FOR DWARF SPHEROIDAL GALAXIES?

By M. Walker, M. Mateo, E. Olszewski, J. Peñarrubia, N. Evans II, G. Gilmore. 2009

495 citations recorded by the source corpus.

We apply the Jeans equation to estimate masses for eight of the brightest dwarf spheroidal (dSph) galaxies. For Fornax, the dSph with the largest kinematic data set, we obtain a model-independent constraint on the maximum circular velocity, Vmax = 20+4−3 km s−1. Although we obtain only lower limits of Vmax ≳ 10 km s−1 for the remaining dSphs, we find that in all cases the enclosed mass at the projected half-light radius is well constrained and robust to a wide range of halo models and velocity anisotropies. We derive a simple analytic formula that estimates M(rhalf) accurately with respect to results from the full Jeans analysis. Applying this formula to the entire population of Local Group dSphs with published kinematic data, we demonstrate a correlation such that M(rhalf) ∝ r1.4±0.4half, or in terms of the mean density interior to the half-light radius, 〈ρ〉 ∝ r−1.6±0.4half. This relation is driven by the fact that the dSph data exhibit a correlation between global velocity dispersion and half-light radius. We argue that tidal forces are unlikely to have introduced this relation, but tides may have increased the scatter and/or altered the slope. While the data are well described by mass profiles ranging over a factor of ≲2 in normalization (Vmax ∼ 10–20 km s−1), we consider the hypothesis that all dSphs are embedded within a “universal” dark matter halo. We show that in addition to the power law M ∝ r1.4, viable candidates include a cuspy “Navarro–Frenk–White” halo with Vmax ∼ 15 km s−1 and scale radius r0 ∼ 800 pc, as well as a cored halo with Vmax ∼ 13 km s−1 and r0 ∼ 150 pc. Finally, assuming that their measured velocity dispersions accurately reflect their masses, the smallest dSphs now allow us to resolve dSph densities at radii as small as a few tens of pc. At these small scales, we find mean densities as large as 〈ρ〉 ≲ 5 M☉ pc−3 (≲200 GeV cm−3).

View Paper: https://www.semanticscholar.org/paper/a65bbc005edd3464aafe099101d434f2d93a1d46

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

Citations in the corpus

A COMPLETE SPECTROSCOPIC SURVEY OF THE MILKY WAY SATELLITE SEGUE 1: THE DARKEST GALAXY (2010, methodology): “Next, we use the sample defined by the Walker et al. (2009b) EM algorithm.”
Galactic stellar haloes in the CDM model (2009, background): “These simulations can resolve structures down to ∼106 M , comparable to the least massive dark halo hosts inferred for Milky Way satellites (e.g. Strigari et al. 2007; Walker et al. 2009).”
The Dynamical and Chemical Evolution of Dwarf Spheroidal Galaxies with GEAR (2009, background): “The tidal and core radii are taken from Irwin & Hatzidimitriou (1995) and the velocity dispersions from Walker et al. (2009a). followed by a sharp decrease: the feedback energy acts to inhibit star formation.”
Gravitational probes of dark matter physics (2017, background): “Although there is a degeneracy between the velocity anisotropy of stellar orbits, the mass profile of dark matter, and the stellar density profile, the degeneracies can be approximately broken at one point in a dwarf galaxy: the half-light radius [249, 321, 143].”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, methodology): “The blue and red lines are the best-fitting ‘universal profiles’ for dwarf galaxies from Walker et al. (2009).”
The impact of dark matter cusps and cores on the satellite galaxy population around spiral galaxies (2010, background): “…2010 and references therein), recent contributions have shown that the satellite mass enclosed within both the projected and tri-dimensional half-light radii of these systems is well constrained and robust to a wide range of halo models and velocity anisotropies (Walker et al. 2009, Wolf et al.”
SEARCH FOR DARK MATTER SATELLITES USING FERMI-LAT (2012, unknown): “The central mass of Draco is well known from stellar kinematics (Strigari et al. 2008; Walker et al. 2009; Wolf et al. 2010); however, the total dark matter mass for Draco is less certain due to the lack of kinematic measurements in the outer regions of the halo.”
The AIMSS Project I: bridging the star cluster, galaxy divide (2014, background): “Data on the MW and M31 dSph/dE systems come from Walker et al. (2009), McConnachie (2012), Tollerud et al. (2012, 2013), and references therein.”
Disruption of Dark Matter Substructure: Fact or Fiction? (2017, background): “The detailed structure of subhaloes can be tested using kinematic data of dwarf galaxies (e.g., Mateo et al. 1993; Walker et al. 2009; Łokas 2009).”
A White Paper on keV sterile neutrino Dark Matter (2016, background): “The size of such samples has increased from hundreds to thousands in recent years [496, 497].”
The Milky Way’s bright satellites as an apparent failure of ΛCDM (2011, background): “Strigari et al. (2007a), Walker et al. (2009) and Wolf et al. (2010) have shown that the dynamical masses of the MW dSphs within a radius comparable to their stellar extent are well-constrained by kinematic data.”
Galactic Searches for Dark Matter (2012, methodology): “…criteria to the data samples, a maximum likelihood analysis that utilizes Equation 36 provides the integrated dark matter mass within a fixed physical radius r, for an assumed parameterization for the dark matter density profile (Strigari et al., 2008; Martinez et al., 2009; Walker et al., 2009).”
One Law to Rule Them All: The Radial Acceleration Relation of Galaxies (2016, background): “They are coded as follows: 1: Pietrzyński et al. (2009), 2: Irwin & Hatzidimitriou (1995), 3: Walker et al. (2009c), 4: Bonanos et al. (2004), 5: Martin et al. (2008), 6: Walker et al. (2007), 7: Bellazzini et al. (2004), 8: Mateo et al. (2008), 9: Bellazzini et al. (2005), 10: Koch et al. (2007),…”
WHY BARYONS MATTER: THE KINEMATICS OF DWARF SPHEROIDAL SATELLITES (2012, background): “Because most dwarfs show flat σ profiles (Walker et al. 2009), it is assumed that vc(r1/2) is roughly equal to vmax.”
DWARF GALAXY ANNIHILATION AND DECAY EMISSION PROFILES FOR DARK MATTER EXPERIMENTS (2014, methodology): “For Leo V, we adopt the stellar-kinematic data published by Walker et al. (2009a).”
BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES (2012, background): “…2012), and observed in satellites (Kleyna et al. 2002, 2003; Mashchenko et al. 2005; Goerdt et al. 2006; Strigari et al. 2006; Gilmore et al. 2007; Walker et al. 2009; Strigari et al. 2010; Walker & Peñarrubia 2011; Jardel & Gebhardt 2012; Wolf & Bullock 2012; Hayashi & Chiba 2012; Salucci et…”
Subhaloes in self-interacting galactic dark matter haloes (2012, background): “Models that successfully reproduce the observed data tend to have roughly the same value of the enclosed mass within the half-light radius (e.g. Strigari et al. 2007; Peñarrubia et al. 2008; Walker et al. 2009; Wolf et al. 2010).”