Galaxy threshing and the origin of ultra-compact dwarf galaxies in the Fornax cluster

By Kenji Bekki, W. Couch, Michael Drinkwater, Y. Shioya. 2003

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A recent all-object spectroscopic survey centred on the Fornax cluster of galaxies has discovered a population of subluminous and extremely compact members, called 'ultra-compact dwarf' (UCD) galaxies. In order to clarify the origin of these objects, we have used self-consistent numerical simulations to study the dynamical evolution a nucleated dwarf galaxy would undergo if orbiting the centre of the Fornax cluster and suffering from its strong tidal gravitational field. We find that the outer stellar components of a nucleated dwarf are removed by the strong tidal field of the cluster, whereas the nucleus manages to survive as a result of its initially compact nature. The developed naked nucleus is found to have physical properties (e. g. size and mass) similar to those observed for UCDs. We also find that although this formation process does not have a strong dependence on the initial total luminosity of the nucleated dwarf, it does depend on the radial density profile of the dark halo in the sense that UCDs are less likely to be formed from dwarfs embedded in dark matter haloes with central 'cuspy' density profiles. Our simulations also suggest that very massive and compact stellar systems can be rapidly and efficiently formed in the central regions of dwarfs through the merging of smaller star clusters. We provide some theoretical predictions on the total number and radial number density profile of UCDs in a cluster and their dependencies on cluster masses.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a3059a2cffa43e446de5b3c644f4656ac9679ea1

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Citations in the corpus

The ACS Virgo Cluster Survey. VII. Resolving the Connection between Globular Clusters and Ultracompact Dwarf Galaxies (2005, background): “More recent simulations (e.g., Bekki et al. 2001, 2003, 2004) have generally confirmed the findings of Bassino et al. (1994) that, although nonnucleated dwarf elliptical galaxies disintegrate completely after a few passages close to a giant galaxy like M87, the nuclei of more massive dE,N galaxies…”
THE NEXT GENERATION VIRGO CLUSTER SURVEY (NGVS). I. INTRODUCTION TO THE SURVEY (2012, background): “Leading theories for the formation of UCDs include hierarchical merging of stellar clusters, possibly in actively starforming environments (e.g., Fellhauer & Kroupa 2002) and tidal stripping of nucleated galaxies (e.g., Bekki et al. 2003; see also Bassino et al. 1994).”
WIDE-FIELD PRECISION KINEMATICS OF THE M87 GLOBULAR CLUSTER SYSTEM (2011, background): “In this scenario, one would naturally expect them to be on preferentially radial orbits (Bassino et al. 1994; Bekki et al. 2003, although Goerdt et al. 2008 found more complicated orbital trends).”
From star clusters to dwarf galaxies: the properties of dynamically hot stellar systems (2008, background): “Also G1 and ω Cen are classified as MCOs instead of 5 Note that the scenario Bekki et al. (2003) proposes is inconsistent with Λ CDM theory, because it has to assume that the DM haloes of the progenitors of the UCDs are cored instead of cusped.”
Families of dynamically hot stellar systems over 10 orders of magnitude in mass (2011, background): “These objects might originate from larger and more luminous galaxies, now being transformed by tidal interactions with a major host galaxy (e.g. Bekki et al. 2001, 2003; Drinkwater et al. 2003).”
Globular Clusters in Virgo Ellipticals: Unexpected Results for Giants and Dwarfs from Advanced Camera for Surveys Imaging (2005, background): “The nuclei of ‘‘threshed’’ dEs are expected to be centrally concentrated (Bekki et al. 2003), but in the Galaxy, M54 and another candidate nucleus, NGC 2419 (van den Bergh &Mackey 2004), are located at quite large galactocentric radii.”
Nuclear star clusters (2009, background): “The gravitationally self-bound NSCs in these galaxies are likely to survive this disruption process (Bassino et al. 1994; Bekki et al. 2003; Pfeffer and Baumgardt 2013) and will continue their lives orbiting in the halo of the larger galaxy.”
Quantifying the coexistence of massive black holes and dense nuclear star clusters (2009, background): “Taken from Gültekin et al. (2009). globular clusters included here are of interest for scenarioes in which they may be the relic nuclei of stripped galaxies (e.g. Freeman 1993; Bassino et al. 1994; Meylan et al. 2001; Bekki et al. 2003; Walcher et al. 2005).”
Extragalactic Globular Clusters and Galaxy Formation (2006, background): “It has been suggested from simulations (Bekki et al. 2003) that NGC 1399 might have stripped the outermost GCs from the nearby E NGC 1404, leaving it with an anomalously low SN (NGC 1399 has a high SN of ∼ 5 − 6, typical of cluster Es).”
THE RELATIONSHIPS AMONG COMPACT STELLAR SYSTEMS: A FRESH VIEW OF ULTRACOMPACT DWARFS (2011, background): “…number density distribution, a projected velocity dispersion profile that declines strongly with distance, and a peaky, broadwinged shape to their line-of-sight velocity distribution (see Bassino et al. 1994; Bekki et al. 2003; Bekki 2007; Goerdt et al. 2008; Thomas et al. 2008).”
GALAXIES AT THE EXTREMES: ULTRA-DIFFUSE GALAXIES IN THE VIRGO CLUSTER (2015, background): “Complete tidal disruption may leave behind their high density nuclei, leading to the formation of ultracompact dwarf galaxies (UCDs; Bekki et al. 2003; Pfeffer & Baumgardt 2013).”