Constraints on the Shape of the Milky Way Dark Matter Halo From the Sagittarius Stream

Vera-Ciro, Carlos; Helmi, Amina

doi:10.1088/2041-8205/773/1/l4

Cited by 146 publications

(137 citation statements)

References 38 publications

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“…Although, for the streams, the original model of Law & Majewski (2010a) predicted a different trend of line-of-sight velocity with angular phase than observed, the more recent model of Vera-Ciro & Helmi (2013), in which the dark halo of the Galaxy is oblate near the centre and significantly triaxial at large distances (and which includes the gravitational effect of the Large Magellanic Could), fares better. Interestingly, the tangential velocity predicted by this model (see the righthand-side of …”

Section: The Orbit Of Ngc 2419mentioning

confidence: 84%

The power of teaming up HST andGaia: the first proper motion measurement of the distant cluster NGC 2419

Massari

Posti

Helmi

et al. 2017

A&A

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Aims. We present the first measurement of the proper motion and orbit of the very distant and intriguing globular cluster NCG 2419. Methods. We have combined data from HST and Gaia DR1 to derive the relative proper motions of stars in the direction of the cluster. To tie these to an absolute reference frame, we have used a background galaxy located in the field. Results. We find the absolute proper motion of NGC 2419 to be (µ α cos(δ), µ δ ) = (−0.17 ± 0.26, −0.49 ± 0.17) mas yr −1 . We have integrated the orbit of the cluster in a Galactic potential and found it to oscillate between ∼53 kpc and ∼98 kpc on an almost polar orbit. This, and the fact that it shares the same sense of rotation around the Milky Way, make it very likely that NGC 2419 is a former cluster of the Sagittarius dwarf spheroidal galaxy.

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Section: The Orbit Of Ngc 2419mentioning

confidence: 84%

The power of teaming up HST andGaia: the first proper motion measurement of the distant cluster NGC 2419

Massari

Posti

Helmi

et al. 2017

A&A

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“…Figure 10 compares our measured distances to two N-body models for the Sagittarius stream-by Law & Majewski (2010) and Peñarrubia et al (2010)-as well as the Sagittarius orbit model of Vera-Ciro & Helmi (2013). The two N-body models, in the upper and middle panels, are shown as density contours (where the darker gray corresponds to a higher density of model particles).…”

Section: Comparison With Numerical Modelsmentioning

confidence: 99%

The Next Generation Virgo Cluster Survey. Xix. Tomography of Milky Way Substructures in the NGVS Footprint

Lokhorst

Starkenburg

McConnachie

et al. 2016

ApJ

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The Next Generation Virgo Cluster Survey (NGVS) is a deep u * giz survey targeting the Virgo Cluster of galaxies at 16.5 Mpc. This survey provides high-quality photometry over an ∼100 deg 2 region straddling the constellations of Virgo and Coma Berenices. This sightline through the Milky Way is noteworthy in that it intersects two of the most prominent substructures in the Galactic halo: the Virgo overdensity (VOD) and Sagittarius stellar stream (close to its bifurcation point). In this paper, we use deep u * gi imaging from the NGVS to perform tomography of the VOD and Sagittarius stream using main-sequence turnoff (MSTO) stars as a halo tracer population. The VOD, whose centroid is known to lie at somewhat lower declinations (α ∼ 190°, δ ∼ −5°) than is covered by the NGVS, is nevertheless clearly detected in the NGVS footprint at distances between ∼8 and 25 kpc. By contrast, the Sagittarius stream is found to slice directly across the NGVS field at distances between 25 and 40 kpc, with a density maximum at ;35 kpc. No evidence is found for new substructures beyond the Sagittarius stream, at least out to a distance of ∼90 kpc-the largest distance to which we can reliably trace the halo using MSTO stars. We find clear evidence for a distance gradient in the Sagittarius stream across the ∼30°of sky covered by the NGVS and its flanking fields. We compare our distance measurements along the stream withthose predicted by leading stream models.

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“…That said, our over-simplification of the Galactic potential is only permissible in a first attempt to fit data with action-based DFs, and should be superseded in later work. In particular, evidence on the shape of the dark matter halo of the Galaxy is confused, and trivial as well as axisymmetric shapes remain possible (e.g., Law et al 2009;Law & Majewski 2010;Vera-Ciro & Helmi 2013;Deg & Widrow 2013). In a spherical potential, the actions are the azimuthal action J φ , which is equal to the angular momentum about the z-axis; the latitudinal action J θ = L − |J φ |, where L is the specific angular momentum, and the radial action…”

Section: Distribution Function and Gravitational Potentialmentioning

confidence: 99%

Haloes light and dark: dynamical models of the stellar halo and constraints on the mass of the Galaxy

Williams

Evans

2015

Mon. Not. R. Astron. Soc.

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We develop a flexible set of action-based distribution functions (DFs) for stellar haloes. The DFs have five free parameters, controlling the inner and outer density slope, break radius, flattening and anisotropy respectively. The DFs generate flattened stellar haloes with a rapidly varying logarithmic slope in density, as well as a spherically aligned velocity ellipsoid with a long axis that points towards the Galactic centre -all attributes possessed by the stellar halo of the Milky Way. We use our action-based distribution function to model the blue horizontal branch stars extracted from the Sloan Digital Sky Survey as stellar halo tracers in a spherical Galactic potential. As the selection function is hard to model, we fix the density law from earlier studies and solve for the anisotropy and gravitational potential parameters. Our best fit model has a velocity anisotropy that becomes more radially anisotropic on moving outwards. It changes from β ≈ 0.4 at Galactocentric radius of 15 kpc to ≈ 0.7 at 60 kpc. This is a gentler increase than is typically found in simulations of stellar haloes built from the mutiple accretion of smaller systems. We find the potential corresponds to an almost flat rotation curve with amplitude of ≈ 200 kms −1 at these distances. This implies an enclosed mass of ≈ 4.5 × 10 11 M within a spherical shell of radius 50 kpc.

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Constraints on the Shape of the Milky Way Dark Matter Halo From the Sagittarius Stream

Cited by 146 publications

References 38 publications

The power of teaming up HST andGaia: the first proper motion measurement of the distant cluster NGC 2419

The power of teaming up HST andGaia: the first proper motion measurement of the distant cluster NGC 2419

The Next Generation Virgo Cluster Survey. Xix. Tomography of Milky Way Substructures in the NGVS Footprint

Haloes light and dark: dynamical models of the stellar halo and constraints on the mass of the Galaxy

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