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 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 Formation of globular clusters with multiple stellar populations from massive gas clumps in high-z gas-rich dwarf galaxies

2019 ◽  
Vol 622 ◽  
pp. A53 ◽  
Author(s):  
K. Bekki
Keyword(s):  
Mass Fraction ◽  
Total Mass ◽  
Globular Clusters ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Stellar Populations ◽  
Stellar Systems ◽  
Agb Stars ◽  
Time Step ◽  
Gas Accretion

Context. One of the currently favored scenarios for the formation of globular clusters (GCs) with multiple stellar populations is that an initial massive stellar system forms (“first generation”, FG), subsequently giving rise to gaseous ejecta which is converted into a second-generation (SG) of stars to form a GC. How such GCs with such FG and SG populations form and evolve, however, remains unclear. Aims. We therefore investigate, for the first time, the sequential formation processes of both FG and SG stars from star-forming massive gas clumps in gas-rich dwarf disk galaxies. Methods. We adopt a novel approach to resolve the two-stage formation of GCs in hydrodynamical simulations of dwarf galaxies. In the new simulations, new gas particles that are much less massive than their parent star particle are generated around each new star particle when the new star enters into the asymptotic giant branch (AGB) phase. Furthermore, much finer maximum time step width (~105 yr) and smaller softening length (~2 pc) are adopted for such AGB gas particles to properly resolve the ejection of gas from AGB stars and AGB feedback effects. Therefore, secondary star formation from AGB ejecta can be properly investigated in galaxy-scale simulations. Results. An FG stellar system can first form from a massive gas clump developing due to gravitational instability within its host gas-rich dwarf galaxy. Initially the FG stellar system is not a single massive cluster, but instead is composed of several irregular stellar clumps (or filaments) with a total mass larger than 106 M⊙. While the FG system is dynamically relaxing, gaseous ejecta from AGB stars can be gravitationally trapped by the FG system and subsequently converted into new stars to form a compact SG stellar system within the FG system. Interestingly, about 40% of AGB ejecta is from stars that do not belong to the FG system (“external gas accretion”). FG and SG stellar systems have different amplitudes of internal rotation and V∕σ. The mass-density (MSG−ρSG) relation for SG stellar systems can be approximated as ρSG ∝ MSG1.5. There can be a threshold total mass of GC host galaxies (Mth = [5 − 23] × 109 M⊙) beyond which the formation of GCs with compact SG stellar systems is possible. Both the initial baryonic mass fraction and the gas mass fraction in dwarfs are crucial parameters that determine whether or not GCs can contain multiple stellar populations. GCs with compact SG stellar systems are more likely to form in dwarf disks with larger gas mass fractions and higher surface mass densities. Formation of binary GCs with SGs and the subsequent GC merging are clearly seen in some models. The derived external gas-accretion process in FG systems initially consisting of stellar clumps will need to be investigated further in more sophisticated simulations.

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 Nucleosynthesis in the Stellar Systems ω Centauri and M22

2011 ◽  
Vol 28 (1) ◽  
pp. 28-37 ◽  
Author(s):  
G. S. Da Costa ◽  
A. F. Marino
Keyword(s):  
Globular Cluster ◽  
Total Mass ◽  
Large Range ◽  
Stellar System ◽  
Stellar Systems ◽  
Elemental Abundances ◽  
Two Systems ◽  
Red Giant ◽  
Using Data ◽  
Giant Branch Stars

AbstractThe stellar system ω Centauri (ω Cen) is well known for the large range in elemental abundances among its member stars. Recent work has indicated that the globular cluster M22 (NGC 6656) also possesses an internal abundance range, albeit substantially smallerthan that in ω Cen. Here we compare, as a function of [Fe/H], element-to-iron ratios in the two systems for a number of different elements using data from abundance analyses of red giant branch stars. It appears that the nucleosynthetic enrichment processes were very similar in these two systems despite the substantial difference in total mass.

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 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.

scholarly journals The impact of galaxy harassment on the globular cluster systems of early-type cluster dwarf galaxies

2012 ◽  
Vol 429 (2) ◽  
pp. 1066-1079 ◽  
Author(s):  
R. Smith ◽  
R. Sánchez-Janssen ◽  
M. Fellhauer ◽  
T. H. Puzia ◽  
J. A. L. Aguerri ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Dwarf Galaxies ◽  
Early Type ◽  
Cluster Systems ◽  
The Impact
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