The ACS Virgo Cluster Survey. VII. Resolving the Connection between Globular Clusters and Ultracompact Dwarf Galaxies

Haşegan, Monica; Jordán, Andrés; Côté, Patrick; Djorgovski, S. G.; McLaughlin, Dean E.; Blakeslee, John P.; Mei, S.; West, Michael J.; Peng, Eric W.; Ferrarese, Laura; Milosavljević, Miloš; Tonry, J.; Merritt, David

doi:10.1086/430342

Cited by 269 publications

(590 citation statements)

References 78 publications

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“…It is worth mentioning, however, that they are well worth a study on their own, because they contain important clues for the GCLF formation and overall shape (see the discussions by McLaughlin 1994;Richtler 2003Richtler , 2006, and because they represent a link between the star clusters and the so-called Ultra Compact Galaxies or Dwarf-Galaxy Transition Objects (Hilker et al 1999;Haşegan et al 2005;Rejkuba et al 2007;Mieske et al 2002Mieske et al , 2008.…”

Section: A Historical Notementioning

confidence: 99%

Globular cluster luminosity function as distance indicator

Rejkuba¹

2012

Astrophys Space Sci

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Globular cluster luminosity function as distance indicatorM. Rejkuba 1 Globular clusters are among the first objects used to establish the distance scale of the Universe. In the 1970-ies it has been recognized that the differential magnitude distribution of old globular clusters is very similar in different galaxies presenting a peak at M V ∼ −7.5. This peak magnitude of the so-called Globular Cluster Luminosity Function has been then established as a secondary distance indicator. The intrinsic accuracy of the method has been estimated to be of the order of ∼ 0.2 mag, competitive with other distance determination methods. Lately the study of the Globular Cluster Systems has been used more as a tool for galaxy formation and evolution, and less so for distance determinations. Nevertheless, the collection of homogeneous and large datasets with the ACS on board HST presented new insights on the usefulness of the Globular Cluster Luminosity Function as distance indicator. I discuss here recent results based on observational and theoretical studies, which show that this distance indicator depends on complex physics of the cluster formation and dynamical evolution, and thus can have dependencies on Hubble type, environment and dynamical history of the host galaxy. While the corrections are often relatively small, they can amount to important systematic differences that make the Globular Cluster Luminosity Function a less accurate distance indicator with respect to some other standard candles.

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Section: A Historical Notementioning

confidence: 99%

Globular cluster luminosity function as distance indicator

Rejkuba¹

2012

Astrophys Space Sci

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“…Phillipps et al (2001) interpreted these objects as a new type of galaxy and reflected this notion in the name "ultracompact dwarf galaxy" (UCD). Next to the Fornax Cluster, many UCDs have been found also in other clusters like the Virgo Cluster (Haşegan et al 2005;Evstigneeva et al 2007), the Centaurus Cluster (Mieske et al 2007), the Coma Cluster (Madrid et al 2010), and the Hydra Cluster . While most known UCDs belong to elliptical galaxies in cluster environments, they have also been observed in rather isolated objects like the Sombrero galaxy M 104 (Hau et al 2009) or the group elliptical NGC 3923 (Norris & Kannappan 2011).…”

Section: Introductionmentioning

confidence: 99%

A catalog of extended clusters and ultra-compact dwarf galaxies

Kroupa

2012

A&A

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Context. In the past decade, very extended old stellar clusters with masses in the range from a few 10 4 to 10 8 M and effective radii larger than 10 pc have been found in various types of galaxies in different environments. Objects with masses comparable to normal globular clusters (GCs) are called extended clusters (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies (UCDs). Aims. The paper analyses the observational parameters total luminosity, M V , effective radius, r eff , and projected distance to the host galaxy, R proj , of all known ECs and UCDs and the dependence of these parameters on the type and the total luminosity of their host galaxy. Methods. We searched the available literature to compile a catalog of star clusters with effective radii larger than 10 pc. As there is no clear distinction between ECs and UCDs, both types of objects will be called extended stellar objects -abbreviated "EOs" -in this paper.Results. In total, we found 813 EOs of which 171 are associated with late-type galaxies and 642 EOs associated with early-type galaxies. EOs cover a luminosity range from about M V = −4 to −14 mag. However, the vast majority of EOs brighter than M V = −10 mag are associated with giant elliptical galaxies. At each magnitude extended objects are found with effective radii between 10 pc and an upper size limit, which shows a clear trend: the more luminous the object the larger is the upper size limit. For EOs associated with early-and late-type galaxies, the EO luminosity functions peak at −6.40 mag and −6.47 mag, respectively, which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the r eff vs. M V parameter space, while there is a clear gap between EOs and early-type dwarf galaxies. However, there is a small potential overlap at the high-mass end, where the most extended EOs are close to the parameters of some compact elliptical galaxies. We compare the EO sample with the numerical models of a previous paper and conclude that the parameters of the EO sample as a whole can be very well explained by a star cluster origin, where EOs are the results of merged star clusters of cluster complexes.

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“…The first issue is related to the observed high M/L ratio (between 6 and 9 in solar units) recently reported for UCDs (Haşegan et al 2005). One has to note here that the M/L ratio of UCDs is still debated (Micheal Drinkwater, private communication, compare Evstigneeva et al 2007 who quote a M/L for UCDs 3 and 5 in solar units).…”

Section: Introductionmentioning

confidence: 85%

“…However, we show that the first scenario produces UCDs that are underluminous and contain no dark matter -the sinking process ejects most of the dark matter particles from the halo centre. The stars, which consist the globulars, would replace the dark matter particles and expel them from the centre of the halo (El-Zant, Shlosman & Hoffman 2001;Merritt et al 2004) lowering the M/L ratio beyond observational constraints (Haşegan et al 2005). The other drawbacks of this model is that it is very unlikely to have so many globular cluster in a halo of that size.…”

Section: Discussionmentioning

confidence: 99%

“…If we assume a mass to light ratio of three, we expect an absolute visual magnitude of -11 for the final object. For comparison, a typical UCDs found in Fornax has a central velocity dispersion of 22 km/s, an absolute magnitude of -12 and a half mass radius of 25 pc (Haşegan et al 2005;Drinkwater et al 2003). In order to form this system by merging globular clusters one would need to consider many more globulars to reach the observed luminosity.…”

Section: The Globular Cluster Simulationsmentioning

confidence: 99%

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The Formation of Ultra-Compact Dwarf Galaxies and Nucleated Dwarf Galaxies

Goerdt

2011

Astrophysics and Space Science Proceedings

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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 nuclei give a more promising explanation, especially if the nuclei form via the sinking of gas, funneled down inner galactic bars, since this process enhances the central dark matter content. Even when the entire disk is tidally stripped away, the nucleus stays intact and can remain dark matter dominated even after severe stripping. Total galaxy disruption beyond the nuclei only occurs on certain orbits and depends on the amount of dissipation during nuclei formation. By comparing the total disruption of CDM subhaloes in a cluster potential we demonstrate that this model also leads to the observed spatial distribution of UCDs which can be tested in more detail with larger data sets.

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The ACS Virgo Cluster Survey. VII. Resolving the Connection between Globular Clusters and Ultracompact Dwarf Galaxies

Cited by 269 publications

References 78 publications

Globular cluster luminosity function as distance indicator

Globular cluster luminosity function as distance indicator

A catalog of extended clusters and ultra-compact dwarf galaxies

The Formation of Ultra-Compact Dwarf Galaxies and Nucleated Dwarf Galaxies

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