The formation of ultra-compact dwarf galaxies and nucleated dwarf galaxies
Tobias Goerdt (1,2), Ben Moore (1), Stelios Kazantzidis (3), Tobias, Kaufmann (4), Andrea V. Macci\`o (5), Joachim Stadel (1), ((1) University of, Z\"urich, (2) HU Jerusalem, (3) KIPAC, Stanford, (4) UC Irvine, (5), MPIA-Heidelberg)

TL;DR
This study uses high-resolution simulations to explore two formation scenarios for ultra-compact dwarf galaxies, finding that stripped galactic nuclei with gas inflow best match observed properties and dark matter content.
Contribution
It demonstrates that the formation of UCDs via stripped galactic nuclei with gas inflow explains their properties better than globular cluster mergers, highlighting the importance of dissipation and dark matter retention.
Findings
Stripped nuclei can retain dark matter after severe tidal stripping.
Globular cluster mergers produce underluminous UCDs with no dark matter.
The spatial distribution of UCDs supports the stripped nucleus formation model.
Abstract
Ultra compact dwarf galaxies (UCDs) have similar properties as massive globular clusters or the nuclei of nucleated galaxies. Recent observations suggesting a high dark matter content and a steep spatial distribution within groups and clusters provide new clues as to their origins. We perform high-resolution N-body / smoothed particle hydrodynamics simulations designed to elucidate two possible formation mechanisms for these systems: the merging of globular clusters in the centre of a dark matter halo, or the massively stripped remnant of a nucleated galaxy. Both models produce density profiles as well as the half light radii that can fit the observational constraints. However, we show that the first scenario results to UCDs that are underluminous and contain no dark matter. This is because the sinking process ejects most of the dark matter particles from the halo centre. Stripped…
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