The HST/ACS Coma Cluster Survey - X. Nuclear star clusters in low-mass early-type galaxies: scaling relations

Mark den Brok*, Reynier F. Peletier, Anil Seth, Marc Balcells, Lilian Dominguez, Alister W. Graham, David Carter, Peter Erwin, Henry C. Ferguson, Paul Goudfrooij, Rafael Guzman, Carlos Hoyos, Shardha Jogee, John Lucey, Steven Phillipps, Thomas Puzia, Edwin Valentijn, Gijs Verdoes Kleijn, Tim Weinzirl

*Corresponding author for this work

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Abstract

We present scaling relations between structural properties of nuclear star clusters and their host galaxies for a sample of early-type dwarf galaxies observed as part of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) Coma Cluster Survey. We have analysed the light profiles of 200 early-type dwarf galaxies in the magnitude range 16.0 <m(F814W) <22.6 mag, corresponding to -19.0 <M-F814W <-12.4 mag. Nuclear star clusters are detected in 80 per cent of the galaxies, thus doubling the sample of HST-observed early-type dwarf galaxies with nuclear star clusters. We confirm that the nuclear star cluster detection fraction decreases strongly towards faint magnitudes. The luminosities of nuclear star clusters do not scale linearly with host galaxy luminosity. A linear fit yields L-nuc similar to L-gal(0.57 +/- 0.05). The nuclear star cluster-host galaxy luminosity scaling relation for low-mass early-type dwarf galaxies is consistent with formation by globular cluster (GC) accretion. We find that at similar luminosities, galaxies with higher Sersic indices have slightly more luminous nuclear star clusters. Rounder galaxies have on average more luminous clusters. Some of the nuclear star clusters are resolved, despite the distance of Coma. We argue that the relation between nuclear star cluster mass and size is consistent with both formation by GC accretion and in situ formation. Our data are consistent with GC inspiralling being the dominant mechanism at low masses, although the observed trend with Sersic index suggests that in situ star formation is an important second-order effect.

Original languageEnglish
Pages (from-to)2385-2403
Number of pages19
JournalMonthly Notice of the Royal Astronomical Society
Volume445
Issue number3
DOIs
Publication statusPublished - 11-Dec-2014

Keywords

  • galaxies: dwarf
  • galaxies: nuclei
  • galaxies: star clusters: general
  • HUBBLE-SPACE-TELESCOPE
  • DWARF ELLIPTIC GALAXIES
  • SUPERMASSIVE BLACK-HOLES
  • SPIRAL GALAXIES
  • VIRGO CLUSTER
  • MILKY-WAY
  • GLOBULAR-CLUSTERS
  • HOST GALAXIES
  • STRUCTURAL PARAMETERS
  • KINEMATIC PROPERTIES

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