Scientific Rationale


At the low-mass end of stellar systems, there used to be a well known dichotomy. On the one hand, there are star clusters with typical sizes of a few pc, whose internal dynamics can generally be well described by the Newtonian Gravity law. On the other hand, there are the much more extended dwarf galaxies with sizes of several hundred pc, whose dynamics appear to be dark matter dominated and which are usually related to cosmological substructures. These classical boundaries have been blurred by the recent discovery of new classes of stellar groupings, such as ultrafaint dSphs, ultramassive Super Star Clusters, Ultra Compact Dwarf Galaxies (UCDs), and dark matter poor Tidal Dwarf Galaxies (TDGs). These discoveries and the confirmation of multiple stellar populations in a number of Galactic globular clusters have reinforced the question to which extent star clusters and dwarf galaxies actually share common origins and are intimately linked in their dynamical evolution.

In this context, recent years have seen a particularly large effort in the astronomical community to thoroughly investigate the internal dynamics of low-mass stellar systems in the Milky Way and Andromeda. Extensive measurements of dwarf spheroidal galaxy kinematics have yielded crucial input for structure formation theories particularly on the clustering properties of dark matter on small scales. Similar observing campaigns regarding Milky Way star clusters are providing strong constraints on theories of modified gravity and on the shape of the M_BH - sigma relation at low masses. Proper motion studies of the Galactic halo have revealed a marked phase-space correlation of dSph orbits which is challenging canonical structure formation paradigms, and alternative explanations to dark matter have been put forward regarding the large velocity dispersions found for dSphs..

Beyond the Local Group, space-based imaging has been extensively used to investigate the dynamical evolution of star cluster populations in a number of star forming galaxies. The initial cluster mass function is distinctly different from the mass function of old globular clusters which is still not very well understood. Also, star clusters and dwarf galaxies have been used as dynamical tracers in galaxies and galaxy clusters, constraining the gravitational potential on large scales. Finally, peculiar internal dynamics were found for UCDs — objects at the phase transition between star clusters and dwarf galaxies — suggesting either dark matter clustering on scales below those suggested for dSphs, or a significant IMF variation.

All this shows that the dynamics of low-mass stellar systems is not only an interesting subject in its own right, but is also intimately
linked to global theories of structure formation, the physics of gravity, and the shape of the stellar initial mass function. Given the wealth of new information gathered most recently in this field, the time is ripe to hold a dedicated meeting on this topic. We aim at
bringing together a mix of astronomers from both observations and theory that work on the dynamics of dwarf galaxies and star clusters.

This Workshop

The workshop topics shall include:

  • Dynamics of dwarf galaxies in the context of LCDM and alternative theories
    • Observed kinematics of classical dSphs, ultrafaint dSphs and tidal dwarfs
    • Dynamical modelling of dwarf galaxies
    • Dynamics of dwarf galaxies in alternative theories of structure formation

  • Dynamics of compact stellar systems
    • Dynamical modelling of compact stellar systems
    • The mass function of young star clusters and globular clusters
    • Tests of Newtonian dynamics in star clusters
    • Internal dynamics of UCDs

  • The dwarf galaxy – star cluster interface
    • Star clusters as progenitors of dwarf galaxies
    • The formation of UCDs

  • The M_BH - sigma relation of low-mass stellar systems
    • The influence of black holes (BHs) on the dynamics of low-mass stellar systems
    • Observational constraints on BH masses in star clusters and dwarf galaxies

  • Star clusters and dwarf galaxies as test particles in galaxy (cluster) potentials
    • Star cluster and dwarf galaxy dynamical evolution in a tidal field [theory]
    • The kinematics of globular cluster systems
    • Observational constraints on the accretion of globular clusters
    • The role of galaxy interactions in shaping the observed dwarf galaxy and star cluster populations


The workshop, limited to 80-100 participants, will take place at the ESO premises in Santiago, Chile.

For further information, contacts us on

The workshop is sponsored by ESO.