English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Open

We present new imaging and spectroscopic observations of six ultra-compactdwarf (UCD) galaxies in the Virgo Cluster, along with re-analysed data for fiveFornax Cluster UCDs. These are the most luminous UCDs: -14<Mv<-12 mag. Our HSTimaging shows that most of the UCDs have shallow or steep cusps in their cores;only one UCD has a flat ``King'' core. None of the UCDs show tidal cutoffs downto our limiting surface brightness. Spectroscopic analysis shows that VirgoUCDs are older than 8 Gyr and have metallicities in the range[Z/H]=-1.35...+0.35 dex. Five Virgo UCDs have super-solar alpha/Fe abundanceratios typical of old stellar populations found in globular clusters andelliptical galaxies. Virgo UCDs have structural and dynamical propertiessimilar to Fornax UCDs. The Virgo and Fornax UCDs all have masses ~2-9x10^7Msun and mass-to-light ratios ~3-5 Msun/Lsun,v. The dynamical M/L values forVirgo UCDs are consistent with SSP model predictions: Virgo UCDs do not requiredark matter to explain their mass-to-light ratios. We conclude that theinternal properties of Virgo UCDs are consistent with them being thehigh-mass/high-luminosity extreme of known globular cluster populations. Werefrain from any firm conclusions on Fornax UCD origins until accurate age,metallicity and alpha-abundance estimates are obtained for them. Some of ourresults, notably the fundamental plane projections are consistent with theformation of UCDs by the simple removal of the halo from the nuclei ofnucleated dwarf galaxies. However the ages, metallicities and abundances forVirgo UCDs are not consistent with this simple stripping model. It might beconsistent with more sophisticated models of the stripping process that includethe effects of gas removal on the chemical evolution of the nuclei.

Address

About

Learn

Download the Zendy App

Discover

Explore