Ultracompact dwarfs in the Perseus Cluster: UCD formation via tidal stripping

Samantha J. Penny*, Duncan A. Forbes, Jay Strader, Christopher Usher, Jean P. Brodie, Aaron J. Romanowsky

*Corresponding author for this work

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We present the results of a Keck/DEIMOS survey of Ultracompact dwarfs (UCDs) in the Perseus Cluster core. We confirm cluster membership for 14 UCDs, with radial velocities ~5300 km s-1. Two of these confirmed that Perseus UCDs have extremely blue colours (B-R < 0.6 mag), reside in star-forming filaments surrounding NGC 1275, and have likely formed as massive star clusters in the last ~100 Myr. We also measure a central velocity dispersion of a third, UCD13 (σ0 = 38 ± 8 km s-1), the most extended UCD in our sample. We determine it to have radius Re = 85 ± 1.1 pc, a dynamical mass of (2.3 ± 0.8) × 108M, and a metallicity [Z/H]= -0.52+0.33-0.29 dex. UCD13 and the cluster's central galaxy, NGC 1275, have a projected separation of 30 kpc and a radial velocity difference of ~20 km s-1. Based on its size, red colour, internal velocity dispersion, dynamical mass, metallicity, and proximity to NGC 1275, we argue that UCD13 is likely the remnant nucleus of a tidally stripped dwarf elliptical (dE), with this progenitor dE having MB ≈ -16 mag and mass ~109M.

Original languageEnglish
Pages (from-to)3808-3816
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date4 Mar 2014
Publication statusPublished - 21 Apr 2014


  • Galaxies: clusters: individual: Perseus Cluster
  • Galaxies: dwarf
  • Galaxies: star clusters: general


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