Discy dwarf disruption and the shape of the Galactic halo

Abstract

The shape of the Galactic dark halo can, in principle, be inferred through modelling of stellar tidal streams in the Milky Way halo. The brightest and the longest of these, the Sagittarius stream, reaches out to large Galactocentric distances and hence can deliver the tightest constraints on the Galaxy's potential. In this contribution, we revisit the idea that the Sagittarius Stream was formed from a rotating progenitor. We demonstrate that the angle between the disk's angular momentum and the progenitor's orbital angular momentum does not remain constant throughout the disruption. Instead, it undergoes a dramatic evolution caused, in part, by the changes in the progenitor's moment of inertia tensor. We show that, even in a spherical potential, the streams produced as a result of a disky dwarf disruption appear to be "precessing". Yet, this debris plane evolution is illusory as it is solely caused by the swaying and wobbling of the progenitor's disk. Stream plane precession is therefore not an unambiguous indicator of asphericity of the dark halo.

arXiv comment5 pages, 5 figures. Updated title to match published version. This is a pre-copyedited, author-produced version of an article accepted for publication in MNRAS following peer review

References in corpus (36)

• The Structure of Cold Dark Matter Halos
• The cosmological simulation code GADGET-2
• The Field of Streams: Sagittarius and its Siblings
• Concentration, Spin and Shape of Dark Matter Haloes as a Function of the Cosmological Model: WMAP1, WMAP3 and WMAP5 results
• The Shape of Dark Matter Halos: Dependence on Mass, Redshift, Radius, and Formation
• The Sagittarius Dwarf Galaxy: a Model for Evolution in a Triaxial Milky Way Halo
• Constraining the Milky Way potential with a 6-D phase-space map of the GD-1 stellar stream
• Halo Properties in Cosmological Simulations of Self-Interacting Cold Dark Matter
• The Metamorphosis of Tidally Stirred Dwarf Galaxies
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: IV. Modeling the Sagittarius Tidal Tails
• The Effect of Gas Cooling on the Shapes of Dark Matter Halos
• "Skinny Milky Way, Please", says Sagittarius
• The Origin of the Bifurcation in the Sagittarius Stream
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: III. Constraints on the Flattening of the Galactic Halo
• Galaxy-Induced Transformation of Dark Matter Halos
• Velocity trends in the debris of Sagittarius and the shape of the dark-matter halo of the Galaxy
• Precession of the Sagittarius stream
• Globular Cluster Streams as Galactic High-Precision Scales - The Poster Child Palomar 5
• The Causes of Halo Shape Changes Induced by Cooling Baryons: Disks Versus Substructures
• The Sagittarius Streams in the Southern Galactic Hemisphere
• The Shape of the Gravitational Potential in Cold Dark Matter Halos
• The Shape of Dark Matter Haloes in the Aquarius Simulations: Evolution and Memory
• Re-Assembling the Sagittarius Dwarf Galaxy
• Was the Progenitor of the Sagittarius Stream a Disc Galaxy?
• Probing the Shape of the Galactic Halo with Hyper-Velocity Stars
• The Resolved Structure and Dynamics of an Isolated Dwarf Galaxy: A VLT and Keck Spectroscopic Survey of WLM
• Tidal debris of dwarf spheroidals as a probe of structure formation models
• Dipping Our Toes in the Water: First Models of GD-1 as a Stream
• On feathers, bifurcations and shells: the dynamics of tidal streams across the mass scale
• Kinematics of hypervelocity stars in the triaxial halo of the Milky Way
• The Tilt of the Halo Velocity Ellipsoid and the Shape of the Milky Way Halo
• No evidence for internal rotation in the remnant core of the Sagittarius dwarf
• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: VII. Kinematics of the Main Body of the Sagittarius dSph
• A Tale Twice Told: The Luminosity Profiles of the Sagittarius Tails
• Efficient N-body Realisations of axisymmetric Galaxies and Haloes
• Constraints on the Shape of the Milky Way Dark Matter Halo from Jeans Equations Applied to SDSS Data

Cited by in corpus (9)

• Tango for three: Sagittarius, LMC, and the Milky Way
• The upper bound on the lowest mass halo
• Stray, swing and scatter: angular momentum evolution of orbits and streams in aspherical potentials
• Full 5D characterisation of the Sagittarius stream with Gaia DR2 RR Lyrae
• Unmixing the Galactic Halo with RR Lyrae tagging
• Connecting the Milky Way potential profile to the orbital timescales and spatial structure of the Sagittarius Stream
• Modelling the stellar halo with RR-Lyrae stars
• An Orbit Fit to Likely Hermus Stream Stars
• A fork in the Sagittarius trailing debris