scholarly journals Ultra compact objects in the Fornax cluster of galaxies: Globular clusters or dwarf galaxies?

2002 ◽  
Vol 383 (3) ◽  
pp. 823-837 ◽  
Author(s):  
S. Mieske ◽  
M. Hilker ◽  
L. Infante
Keyword(s):  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Compact Objects ◽  
Cluster Of Galaxies ◽  
Fornax Cluster

scholarly journals Compact Stellar Systems in the Fornax Cluster: Super-massive Star Clusters or Extremely Compact Dwarf Galaxies?

2000 ◽  
Vol 17 (3) ◽  
pp. 227-233 ◽  
Author(s):  
M. J. Drinkwater ◽  
J. B. Jones ◽  
M. D. Gregg ◽  
S. Phillipps
Keyword(s):  
Globular Clusters ◽  
Massive Star ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Star Clusters ◽  
Compact Objects ◽  
High Dispersion ◽  
Stellar Systems ◽  
Absolute Magnitudes ◽  
Fornax Cluster

AbstractWe describe a population of compact objects in the centre of the Fornax Cluster which were discovered as part of our 2dF Fornax Spectroscopic Survey. These objects have spectra typical of old stellar systems, but are unresolved on photographic sky survey plates. They have absolute magnitudes −13 < MB < −11, so they are 10 times more luminous than any Galactic globular clusters, but fainter than any known compact dwarf galaxies. These objects are all within 30 arcminutes of the central galaxy of the cluster, NGC 1399, but are distributed over larger radii than the globular cluster system of that galaxy. We suggest that these objects are either super-massive star clusters (intra-cluster globular clusters or tidally stripped nuclei of dwarf galaxies) or a new type of low-luminosity, compact elliptical dwarf (‘M32-type”) galaxy. The best way to test these hypotheses will be to obtain high-resolution imaging and high-dispersion spectroscopy to determine their structures and mass-to-light ratios. This will allow us to compare them to known compact objects and establish whether they represent a new class of hitherto unknown stellar system.

scholarly journals An Update on the ACS Virgo and Fornax Cluster Surveys

2007 ◽  
Vol 3 (S246) ◽  
pp. 377-386 ◽  
Author(s):  
Patrick Côté ◽  
Laura Ferrarese ◽  
Andrés Jordán ◽  
John P. Blakeslee ◽  
Chin-Wei Chen ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Milky Way ◽  
Dwarf Galaxies ◽  
Hubble Space Telescope ◽  
Structural Parameters ◽  
Star Clusters ◽  
Early Type ◽  
Space Telescope ◽  
Fornax Cluster ◽  
Selection Of

AbstractWe present a brief update on the ACS Virgo and Fornax Cluster Surveys —Hubble Space Telescopeprograms to obtainACSimaging for 143 early-type galaxies in the two galaxy clusters nearest to the Milky Way. We summarize a selection of science highlights from the surveys as including new results on the central structure of early-type galaxies, the apparent continuity of photometric and structural parameters between dwarf and giant galaxies, and the properties of globular clusters, diffuse star clusters and ultra-compact dwarf galaxies.

scholarly journals Dwarf Galaxies in the Fornax Cluster

1987 ◽  
Vol 127 ◽  
pp. 455-456
Author(s):  
Nelson Caldwell ◽  
Gregory Bothun
Keyword(s):  
Observational Study ◽  
Dwarf Galaxies ◽  
Cluster Of Galaxies ◽  
Fornax Cluster

We present the results of an observational study of the dwarf galaxies in the Fornax cluster of galaxies.

scholarly journals Searching for correlations in Gaia DR2 unbound star trajectories

2019 ◽  
Vol 490 (4) ◽  
pp. 5647-5657
Author(s):  
F Montanari ◽  
D Barrado ◽  
J García-Bellido
Keyword(s):  
Globular Clusters ◽  
Cold Dark Matter ◽  
Dwarf Galaxies ◽  
Compact Objects ◽  
Evolutionary Status ◽  
Primordial Black Hole ◽  
Full Phase Space ◽  
Nearby Galaxies ◽  
Gaia Dr2 ◽  
Scattering Events

ABSTRACT Scattering events with compact objects are expected in the primordial black hole (PBH) cold dark matter (CDM) scenario, due to close encounters between stars and PBHs in the dense environments of dwarf spheroidals. We develop a Bayesian framework to search for correlations among Milky Way stellar trajectories and those of globular clusters and dwarf galaxies in the halo and in other nearby galaxies. We apply the method to a selection of hypervelocity stars (HVS) and globular clusters from the Gaia DR2 catalogue and known nearby (mostly dwarf) galaxies with full phase-space and size measurements. We report positive evidence for trajectory intersection ∼20–40 Myr ago of up to two stars, depending on priors, with the Sagittarius dwarf spheroidal galaxy (dSph) when assuming the distance estimates of Marchetti, Rossi & Brown (2018). We verify that the result is compatible with their evolutionary status, setting a lower bound for their stellar age of ∼100 Myr. However, such scattering events are not confirmed when assuming Anders et al. (2019) distance estimates. We discuss shortcomings related to present data quality and future prospects for detection of HVS with the full Gaia catalogue and Sagittarius dSph.

scholarly journals Stellar population properties of the most massive globular clusters and ultra-compact dwarf galaxies of the Fornax cluster

2015 ◽  
Vol 12 (S316) ◽  
pp. 99-104
Author(s):  
Michael Hilker
Keyword(s):  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Mass Function ◽  
Nearby Galaxy ◽  
Stellar Content ◽  
Medium Resolution ◽  
Low Surface Brightness ◽  
Show Evidence ◽  
Internal Properties ◽  
Fornax Cluster

AbstractMost ultra-compact dwarf galaxies (UCDs) and very massive globular clusters reside in nearby galaxy clusters or around nearby giant galaxies. Due to their distance (> 4 Mpc) and compactness (reff < 100 pc) they are barely resolved, and thus it is difficult to obtain their internal properties. Here I present our most recent attempts to constrain the mass function, stellar content and dynamical state of UCDs in the Fornax cluster. Thanks to radial velocity membership assignment of ~ 950 globular clusters (GCs) and UCDs in the core of Fornax, the shape of their mass function is well constrained. It is consistent with the ‘standard’ Gaussian mass function of GCs. Our recent simulations on the disruption process of nucleated dwarf galaxies in cluster environments showed that ~ 40% of the most massive UCDs should originate from nuclear star clusters. Some Fornax UCDs actually show evidence for this scenario, as revealed by extended low surface brightness disks around them and onsets of tidal tails. Multi-band UV to optical imaging as well as low to medium resolution spectroscopy revealed that there exist UCDs with youngish ages, (sub-)solar [α/Fe] abundances, and probably He-enriched populations.

scholarly journals A Search for Globular Clusters in the Surroundings of Dwarf Galaxies in Fornax: Intracluster Globulars?

2002 ◽  
Vol 207 ◽  
pp. 345-347
Author(s):  
Lilia P. Bassino ◽  
Sergio A. Cellone ◽  
Juan C. Forte
Keyword(s):  
Density Distribution ◽  
Globular Cluster ◽  
Surface Density ◽  
Globular Clusters ◽  
Surface Brightness ◽  
Dwarf Galaxies ◽  
Color Distribution ◽  
Low Surface Brightness ◽  
Fornax Cluster

We present the results of a search for globular clusters in the surroundings of 15 low surface brightness dwarf galaxies in the Fornax cluster, on CCD images in the C and T1 bands. Globular cluster candidates show a clear bimodal color distribution. Their surface density distribution shows no concentration towards the respective dwarf galaxies but it does show concentration towards the center of the Fornax cluster. We suggest that the potential globular clusters might not be bound to the dwarf galaxies, but might instead belong to the intra-cluster medium.

scholarly journals Astroinformatics-based search for globular clusters in the Fornax Deep Survey

2019 ◽  
Vol 490 (3) ◽  
pp. 4080-4106
Author(s):  
G Angora ◽  
M Brescia ◽  
S Cavuoti ◽  
M Paolillo ◽  
G Longo ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Multidisciplinary Approach ◽  
Feature Selection Method ◽  
Principal Component ◽  
Selection Method ◽  
Neural Gas ◽  
The Core ◽  
Cluster Of Galaxies ◽  
Deep Survey ◽  
Fornax Cluster

ABSTRACT In the last years, Astroinformatics has become a well-defined paradigm for many fields of Astronomy. In this work, we demonstrate the potential of a multidisciplinary approach to identify globular clusters (GCs) in the Fornax cluster of galaxies taking advantage of multiband photometry produced by the VLT Survey Telescope using automatic self-adaptive methodologies. The data analysed in this work consist of deep, multiband, partially overlapping images centred on the core of the Fornax cluster. In this work, we use a Neural Gas model, a pure clustering machine learning methodology, to approach the GC detection, while a novel feature selection method (ΦLAB) is exploited to perform the parameter space analysis and optimization. We demonstrate that the use of an Astroinformatics-based methodology is able to provide GC samples that are comparable, in terms of purity and completeness with those obtained using single-band HST data and two approaches based, respectively, on a morpho-photometric and a Principal Component Analysis using the same data discussed in this work.

scholarly journals Ultra-compact Dwarf Galaxies: a New Class of Compact Stellar System Discovered in the Fornax Cluster

2002 ◽  
Vol 207 ◽  
pp. 287-293
Author(s):  
Michael Drinkwater ◽  
Kenji Bekki ◽  
Warrick Couch ◽  
Steve Phillipps ◽  
Bryn Jones ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Stellar Systems ◽  
New Class ◽  
Cluster Of Galaxies ◽  
Magnitude Range ◽  
Fornax Cluster

We have used the 2dF spectrograph on the Anglo-Australian Telescope to obtain a complete spectroscopic sample of all objects in the magnitude range, 16.5 < bJ < 19.8, regardless of morphology, in an area centred on the Fornax Cluster of galaxies. Among the unresolved targets are five objects which are members of the Fornax Cluster. They are extremely compact stellar systems with scale lengths less than 40 parsecs. These ultra-compact dwarfs are unlike any known type of stellar system, being more compact and significantly less luminous than other compact dwarf galaxies, yet much brighter than any globular cluster.

scholarly journals Globular clusters as tracers of the halo assembly of nearby central cluster galaxies

2015 ◽  
Vol 11 (S317) ◽  
pp. 128-133
Author(s):  
Michael Hilker ◽  
Tom Richtler
Keyword(s):  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Nearby Galaxy ◽  
Lower Mass ◽  
Cluster Galaxies ◽  
Central Cluster ◽  
Stellar Halo ◽  
Correlation Space ◽  
Fornax Cluster ◽  
Analytical Approaches

AbstractThe properties of globular cluster systems (GCSs) in the core of the nearby galaxy clusters Fornax and Hydra I are presented. In the Fornax cluster we have gathered the largest radial velocity sample of a GCS system so far, which enables us to identify photometric and kinematic sub-populations around the central galaxy NGC 1399. Moreover, ages, metallicities and [α/Fe] abundances of a sub-sample of 60 bright globular clusters (GCs) with high S/N spectroscopy show a multi-modal distribution in the correlation space of these three parameters, confirming heterogeneous stellar populations in the halo of NGC 1399. In the Hydra I cluster very blue GCs were identified. They are not uniformly distributed around the central galaxies. 3-color photometry including the U-band reveals that some of them are of intermediate age. Their location coincides with a group of dwarf galaxies under disruption. This is evidence of a structurally young stellar halo “still in formation”, which is also supported by kinematic measurements of the halo light that point to a kinematically disturbed system. The most massive GCs divide into generally more extended ultra-compact dwarf galaxies (UCDs) and genuine compact GCs. In both clusters, the spatial distribution and kinematics of UCDs are different from those of genuine GCs. Assuming that some UCDs represent nuclei of stripped galaxies, the properties of those UCDs can be used to trace the assembly of nucleated dwarf galaxies into the halos of central cluster galaxies. We show via semi-analytical approaches within a cosmological simulation that only the most massive UCDs in Fornax-like clusters can be explained by stripped nuclei, whereas the majority of lower mass UCDs belong to the star cluster family.

scholarly journals Globular cluster clustering around ultra compact dwarf galaxies in the halo of NGC 1399

2015 ◽  
Vol 11 (S317) ◽  
pp. 365-366 ◽  
Author(s):  
Karina Voggel ◽  
Michael Hilker ◽  
Tom Richtler
Keyword(s):  
Spatial Distribution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Large Scale ◽  
Dwarf Galaxies ◽  
Dwarf Galaxy ◽  
Star Cluster ◽  
Host Galaxy ◽  
Cluster Complex ◽  
Fornax Cluster

AbstractWe tested the spatial distribution of UCDs and GCs in the halo of NGC 1399 in the Fornax cluster. In particular we tried to find out if globular clusters are more abundant in the vicinity of UCDs than what is expected from their global distribution. A local overabundance of globular clusters was found around UCDs on a scale of 1 kpc compared to what is expected from the large scale distribution of globulars in the host galaxy. This effect is stronger for the metal-poor blue GCs and weaker for the red GCs. An explanation for these clustered globulars is either that they are the remains of a GC system of an ancestor dwarf galaxy before it was stripped to its nucleus, which appears as UCD today. Alternatively these clustered GCs could have been originally part of a super star cluster complex.

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