The nature of UCDs

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dc.contributor.authorMieske, S.
dc.contributor.authorHilker, M.
dc.contributor.authorJordan, A.
dc.contributor.authorInfante, L.
dc.contributor.authorKissler-Patig, M.
dc.contributor.authorRejkuba, M.
dc.contributor.authorRichtler, T.
dc.contributor.authorCote, P.
dc.contributor.authorBaumgardt, H.
dc.contributor.authorWest, M. J.
dc.contributor.authorFerrarese, L.
dc.contributor.authorPeng, E. W.
dc.date.accessioned2025-01-21T01:05:00Z
dc.date.available2025-01-21T01:05:00Z
dc.date.issued2008
dc.description.abstractContext. The internal dynamics of ultra-compact dwarf galaxies (UCDs) has attracted increasing attention, with most of the UCDs studied to date located in the Virgo cluster.
dc.description.abstractAims. Our aim is to perform a comprehensive census of the internal dynamics of UCDs in the Fornax cluster, and to shed light on the nature of the interface between star clusters and galaxies.
dc.description.abstractMethods. We obtained high-resolution spectra of 23 Fornax UCDs with -10.4 > M-V > -13.5 mag (10(6) < M/M-circle dot < 10(8)), using FLAMES/Giraffe at the VLT. This is the largest homogeneous data set of UCD internal dynamics assembled to date. We derive dynamical M/L ratios for 15 UCDs covered by HST imaging.
dc.description.abstractResults. In the M-V -sigma plane, UCDs with M-V < -12 mag are consistent with the extrapolated Faber-Jackson relation for luminous elliptical galaxies, while most of the fainter UCDs are closer to the extrapolated globular cluster (GC) relation. At a given metallicity, Fornax UCDs have, on average, M/L ratios lower by 30-40% than Virgo UCDs, suggesting possible differences in age or dark matter content between Fornax and Virgo UCDs. For our sample of Fornax UCDs we find no significant correlation between M/L ratio and mass. We combine our data with available M/L ratio measurements of compact stellar systems with 104 < M/M-circle dot < 108 M, and normalise all M/L estimates to solar metallicity. We find that UCDs (M >= 2 x 10(6) M-circle dot) have M/L ratios twice as large as GCs (M less than or similar to 2 x 10(6) M-circle dot). We argue that dynamical evolution has probably had only a small effect on the current M/L ratios of objects in the combined sample, implying that stellar population models tend to under-predict dynamical M/L ratios of UCDs and over-predict those of GCs. Considering the scaling relations of stellar spheroids, we find that UCDs align well along the " Fundamental Manifold". UCDs can be considered the small-scale end of the galaxy sequence in this context. The alignment for UCDs is especially clear for r(e) greater than or similar to 7 pc, which corresponds to dynamical relaxation times that exceed a Hubble time. In contrast, globular clusters exhibit a broader scatter and do not appear to align along the manifold.
dc.description.abstractConclusions. We argue that UCDs are the smallest dynamically un-relaxed stellar systems, with M greater than or similar to 2 x 10(6) and 7 less than or similar to r(e)/pc less than or similar to 100. Future studies should aim at explaining the elevated M/L ratios of UCDs and the environmental dependence of their properties.
dc.fuente.origenWOS
dc.identifier.doi10.1051/0004-6361:200810077
dc.identifier.eissn1432-0746
dc.identifier.issn0004-6361
dc.identifier.urihttps://doi.org/10.1051/0004-6361:200810077
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/95779
dc.identifier.wosidWOS:000258328100013
dc.issue.numero3
dc.language.isoen
dc.pagina.finalU17
dc.pagina.inicio921
dc.revistaAstronomy & astrophysics
dc.rightsacceso restringido
dc.subjectgalaxies : clusters : individual : Fornax
dc.subjectgalaxies : dwarf
dc.subjectgalaxies : fundamental parameters
dc.subjectgalaxies : nuclei galaxies : star clusters
dc.titleThe nature of UCDs
dc.typeartículo
dc.volumen487
sipa.indexWOS
sipa.trazabilidadWOS;2025-01-12
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