Cosmic Choreographies

Satellite Galaxy Phase Space Correlations

The research project "Cosmic Coreographies" (COSMICOR), investigates the distribution and motion of satellite dwarf galaxies around more massive hosts, both within and beyond the Local Group. Special emphasis is put on comparisons to cosmological expectations, based on numerical simulations of structure formation.

The group is lead by Dr. Marcel S. Pawlowski, and consists of several team members (see below). The 5-year program is funded as a Leibniz Junior Research Group via the Leibniz Competition since 2021. Further support is provided via a Klaus Tschira Boost Fund by the German Scholars Organization.

Background: Planes of Satellite Galaxies and Other Phase-Space Correlations

The existence of planes of satellite galaxies (see figures below) is one of the most serious unsolved problems of near-field cosmology. We know that the three closest major galaxies in the nearby Universe, including our Milky Way (MW) host such planes: highly flattened structures of satellite galaxies showing signs of coherent rotation, as if their “orbital dance” were performing a cosmic choreography. Similarly extreme arrangements appear to be exceedingly rare in cosmological simulations based on the cold dark matter (CDM) model, giving rise to the Planes of Satellite Galaxies Problem.

Vast Polar Structure of the Milky Way.

The "Vast Polar Structure", the plane of satellites surrounding the Milky Way.

Great Plane of Andromeda

The great plane of satellite galaxies surrounding the Andromeda Galaxy M31.

The Centaurus A Satellite Plane

The plane of satellite galaxies surrounding the massive elliptical galaxy Centaurus A.

With CDM, we have a successful model that explains many large-scale features of the Universe, but we can not fully commit to it until we address this problem. However, our current understanding of satellite galaxy planes is limited because the field has thus far operated in a discovery phase. Now, better numerical models, an unprecedented influx of data on the MW satellites, and upcoming observational facilities provide an opportunity to switch to a different mode: a comprehensive analysis of planes and related phase-space correlations and their tension with the CDM model.

The COSMICOR group's research project is uniquely positioned to address this challenge. Over the next years, we will:

Overview of the Cosmic Choreographies Research Project

Overview of the "Cosmic Choreographies" research project.

  1. identify and characterize the dynamical evolution of satellite phase-space correlations in cosmological simulations, especially constrained ones to for the first time study simulated systems whose environment closely matches that of the nearby Universe;
  2. expand observational studies of satellite systems to larger samples and develop novel metrics of phase-space correlations to address the unique challenges of targeting distant hosts; and
  3. develop a comprehensive understanding of satellite group infall among MW satellites, one of the most promising solutions to the Planes of Satellite Galaxies Problem.

The Team

Current and upcoming members

  • Dr. Marcel S. Pawlowski (Group leader)
  • Dr. Salvatore Taibi (postdoc)
  • Dr. Pengfei Li (Humboldt Fellow, from Winter 2021/22)
  • Jamie Kanehisa (PhD Student, from Fall 2021)
  • Pouria Adel (Bachelor Student)

Past members

  • Jamie Kanehisa (Master student)
Last update: 20. September 2021