What is a Galaxy? Cast your vote here...
Duncan Forbes (Swinburne, Melbourne), Pavel Kroupa (AIfA, Bonn)

TL;DR
This paper explores the criteria that define a galaxy, discussing various properties and proposing a collective voting approach to reach a consensus on the galaxy definition.
Contribution
It introduces a comprehensive discussion on the criteria distinguishing galaxies from star clusters and invites community input through a voting platform.
Findings
Proposes multiple criteria for galaxy classification
Highlights ambiguous cases and their implications
Encourages community consensus on galaxy definitions
Abstract
Although originally classified as galaxies, Ultra Compact Dwarfs (UCDs) share many properties in common with globular star clusters. The debate on the origin and nature of UCDs, and the recently discovered ultra-faint dwarf spheroidal (dSph) galaxies which contain very few stars, has motivated us to ask the question `what is a galaxy?' Our aim here is to promote further discussion of how to define a galaxy and, in particular, what separates it from a star cluster. Like most previous definitions, we adopt the requirement of a gravitationally bound stellar system as a minimum. In order to separate a dwarf galaxy from a globular cluster, we discuss other possible requirements, such as a minimum size, a long two-body relaxation time, a satellite system, the presence of complex stellar populations and non-baryonic dark matter. We briefly mention the implications of each of these definitions…
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