Constraining the Galaxy's dark halo with RAVE stars

By T. Piffl, J. Binney, P. McMillan, Matthias Steinmetz, A. Helmi, R. Wyse, O. Bienaym'e, Joss Bland-Hawthorn, Kenneth C. Freeman, B. Gibson and 10 more. 2014

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We use the kinematics of ∼200000 giant stars that lie within ∼1.5kpc of the plane to measure the vertical profile of mass density near the Sun. We find that the dark mass contained within the isodensity surface of the dark halo that passes through the Sun ((6 ± 0.9) × 10 10 M� ), and the surface density within 0.9kpc of the plane ((69 ± 10)Mpc −2 ) are almost inde- pendent of the (oblate) halo's axis ratio q. If the halo is spherical, 46 per cent of the radial force on the Sun is provided by baryons, and only 4.3 per cent of the Galaxy's mass is baryonic. If the halo is flattened, the baryons contribute even less strongly to the local ra- dial force and to the Galaxy's mass. The dark matter density at the location of the Sun is 0.0126q −0.89 Mpc −3 = 0.48q −0.89 GeVcm −3 . When combined with other literature results we find hints for a mildly oblate dark halo with q � 0.8. Our value for the dark mass within the solar radius is larger than that predicted by cosmological dark-matter-only simulations but in good agreement with simulations once the effects of baryonic infall are taken into account. Our mass models consist of three double-exponential discs, an oblate bulge and a Navarro- Frenk-White dark matter halo, and we model the dynamics of the RAVE (RAdial Velocity Experiment) stars in the corresponding gravitational fields by finding distribution functions f(J) that depend on three action integrals. Statistical errors are completely swamped by systematic uncertainties, the most important of which are the distance to the stars in the pho- tometric and spectroscopic samples and the solar distance to the Galactic Centre. Systematics other than the flattening of the dark halo yield overall uncertainties ∼15percent.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e3518c48b813cd2e5a6b3622bd017222719e4ac6

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Citations in the corpus

galpy: A python LIBRARY FOR GALACTIC DYNAMICS (2014, result): “The local dark-mater density ρDM = 0.008 M pc−3 is in good agreement with current constraints (e.g., Bovy & Tremaine 2012; Zhang et al. 2013; Piffl et al. 2014) as is the escape velocity (e.g., Smith et al. 2007).”
The Milky Way's rotation curve out to 100 kpc and its constraint on the Galactic mass distribution (2016, background): “However, as argued by Kafle et al. (2014) and Piffl et al. (2014), the theoretical relation is constructed from simulations with dark matter only.”
THE RADIAL VELOCITY EXPERIMENT (RAVE): FIFTH DATA RELEASE (2013, methodology): “…recent years a wave-like pattern in the stellar velocity distribution was uncovered (Williams et al. 2013) and the total mass of the Milky Way was measured using the RAVE extreme-velocity stars (Piffl et al. 2014a), as was the local dark matter density (Bienaymé et al. 2014; Piffl et al. 2014b).”
Mass and shape of the Milky Way’s dark matter halo with globular clusters from Gaia and Hubble (2018, methodology): “…e.g. Gonzalez et al. 2013; Eadie & Harris 2016; Sohn et al. 2018), estimates of the escape velocity (e.g. Smith et al. 2007; Piffl et al. 2014a), the velocity distribution of either fast moving stars (e.g. Gnedin et al. 2010) or the dynamics of nearby stars (e.g. McMillan 2011; Piffl et al. 2014b).”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, methodology): “The thin disk is insufficiently constrained in the RAVE survey because the elevated sightlines in latitude do not extend far enough in radius and are susceptible to vertical dispersion gradients (cf. Piffl et al. 2014a, Sanders & Binney 2015).”
The mass distribution and gravitational potential of the Milky Way (2016, background): “Piffl et al.(2014a) also noted that the axis ratio of the dark-matter halo has an important influence on the derived local density when interpreting dynamical models of the disc, withρh,⊙ ∝ q−0.89.”
Dynamical modelling of the galactic bulge and bar: the Milky Way's pattern speed, stellar and dark matter mass distribution (2016, methodology): “Inspired by this, we adopt the three-parameter Einasto density profile given by ρDM(m) = ρ0 exp { − ( 2 α )[( m m0 )α −1 ]} (4) where m = √ x2 + y2 +(z/q)2 is the elliptical radius for an assumed vertical flattening of q = 0.8 (Piffl et al. 2014).”
STARS, GAS, AND DARK MATTER IN THE SOLAR NEIGHBORHOOD (2015, background): “Two new determinations of DMr have appeared since Read (2014)’s review, one by Bienaymé et al. (2014), which we include, and one by Piffl et al. (2014).”
The APOSTLE project: Local Group kinematic mass constraints and simulation candidate selection (2015, background): “…of tracers such as satellite galaxies, halo stars, or tidal debris (see e.g. Battaglia et al. 2005; Sales et al. 2007; Smith et al. 2007; Xue et al. 2008; Watkins, Evans & An 2010; Deason et al. 2012; Boylan-Kolchin et al. 2013; Barber et al. 2014; Piffl et al. 2014, for some recent studies).”
The GALAH survey and Gaia DR2: dissecting the stellar disc’s phase space by age, action, chemistry, and location (2018, methodology): “For given values of the parameters in the DFs, the model’s potential was solved for iteratively after adding the potential of the gas disc assumed by Piffl et al. (2014).”