Globular cluster systems in nearby dwarf galaxies - II. Nuclear star clusters and their relation to massive Galactic globular clusters

Georgiev, Iskren Y., Hilker, Michael, Puzia, Thomas H., Goudfrooij, Paul and Baumgardt, Holger (2009) Globular cluster systems in nearby dwarf galaxies - II. Nuclear star clusters and their relation to massive Galactic globular clusters. Monthly Notices of the Royal Astronomical Society, 396 2: 1075-1085. doi:10.1111/j.1365-2966.2009.14776.x


Author Georgiev, Iskren Y.
Hilker, Michael
Puzia, Thomas H.
Goudfrooij, Paul
Baumgardt, Holger
Title Globular cluster systems in nearby dwarf galaxies - II. Nuclear star clusters and their relation to massive Galactic globular clusters
Journal name Monthly Notices of the Royal Astronomical Society   Check publisher's open access policy
ISSN 0035-8711
1365-2966
Publication date 2009-06
Sub-type Article (original research)
DOI 10.1111/j.1365-2966.2009.14776.x
Open Access Status DOI
Volume 396
Issue 2
Start page 1075
End page 1085
Total pages 11
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Language eng
Formatted abstract
We compare nuclear globular clusters (nGCs) in dwarf galaxies and Galactic GCs with extended (hot) horizontal branches (EHB-GCs) in order to test the suggested external origin of the latter and the conditions at which GC self-enrichment can operate. Using luminosities and structural parameters of nGCs in low-mass (mainly late-type) dwarf galaxies from Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) imaging, we derive the presentday escape velocities (υesc) of stellar ejecta to reach the cluster tidal radius and compare them with those of EHB-GCs. We show that nGCs in dwarf galaxies are very similar in their photometric and structural properties (colour ⟨ V − I ⟩ = 0.9mag, magnitudes ⟨MV⟩ < −9mag, ellipticities ⟨∈⟩ = 0.11) to EHB-GCs. The nGCs populate the same MV versus rh region as EHB-GCs, although they do not reach the sizes of the largest EHB-GCs like ω Cen and NGC2419.We suggest that during accretion the rh of an nGC could increase due to significant mass loss in the cluster vicinity and the resulting drop in the external potential in the core once the dwarf galaxy dissolves. For EHB-GCs, we find a correlation between the present-day υesc and their metallicity as well as (V − I )0 colour. The similar υesc, (V I )0 distribution of nGCs and EHB-GCs imply that nGCs could also have complex stellar populations. The υesc–[Fe/H] relation could reflect the known relation of increasing stellar wind velocity with metallicity, which in turn could explain why more metal-poor clusters typically show more peculiarities in their stellar population than more metal-rich clusters of the same mass do. Thus, the cluster υesc can be used as a parameter to describe the degree of self-enrichment. All our findings support the scenario in which Galactic EHB-GCs have originated in the centres of pre-Galactic building blocks or dwarf galaxies that were later accreted by the Milky Way.
Keyword Galaxies: dwarf
Galaxies: irregular
Galaxies: nuclei
Galaxies: star clusters
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
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