Is the vast polar structure of dwarf galaxies a serious problem for lambda cold dark matter?
arXiv:1612.07325 · doi:10.1093/mnras/stx286
Abstract
The dwarf galaxies around the Milky Way are distributed in a so-called vast polar structure (VPOS) that may be in conflict with Lambda CDM simulations. Here, we seek to determine if the VPOS poses a serious challenge to the Lambda cold dark matter paradigm on galactic scales. Specifically, we investigate if the VPOS remains coherent as a function of time. Using the measured Hubble Space Telescope (HST) proper motions and associated uncertainties, we integrate the orbits of the classical Milky Way satellites backwards in time and find that the structure disperses well before a dynamical time. We also examine in particular Leo I and Leo II using their most recent proper motion data, both of which have extreme kinematic properties, but these satellites do not appear to drive the polar fit that is seen at the present day. We have studied the effect of the uncertainties on the HST proper motions on the coherence of the VPOS as a function of time. We find that 8 of the 11 classical dwarfs have reliable proper motions; for these 8, the VPOS also loses significance in less than a dynamical time, indicating that the VPOS is not a dynamically stable structure. Obtaining more accurate proper motion measurements of Ursa Minor, Sculptor, and Carina would bolster these conclusions.
14 pages, 6 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society. Replacement: expanded discussion, grammar corrected, accepted version of text
References in corpus (20)
- Too big to fail? The puzzling darkness of massive Milky Way subhaloes
- Introducing the Illustris Project: the evolution of galaxy populations across cosmic time
- Are the Magellanic Clouds on their First Passage about the Milky Way?
- A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda Galaxy
- The Velocity Dispersion Profile of the Remote Dwarf Spheroidal Galaxy Leo I: A Tidal Hit and Run?
- The spatial distribution of the Milky Way and Andromeda satellite galaxies
- The Causes of Halo Shape Changes Induced by Cooling Baryons: Disks Versus Substructures
- Co-orbiting satellite galaxy structures are still in conflict with the distribution of primordial dwarf galaxies
- The Space Motion of Leo I: Hubble Space Telescope Proper Motion and Implied Orbit
- Satellites of Simulated Galaxies: survival, merging, and their relation to the dark and stellar halos
- Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. IV: Measurement for Sculptor
- The universal nature of subhalo accretion
- Satellite Systems around Galaxies in Hydrodynamic Simulations
- Inferring the gravitational potential of the Milky Way with a few precisely measured stars
- Alignments between galaxies, satellite systems and haloes
- Comparing the observable properties of dwarf galaxies on and off the Andromeda plane
- A Council of Giants
- The Role of Baryons in Creating Statistically Significant Planes of Satellites around Milky Way-Mass Galaxies
- On the Stability of Satellite Planes I: Effects of Mass, Velocity, Halo Shape and Alignment
- Local Group galaxies emerge from the dark