Publication Date

January 2014

Document Type


Publication Title

Monthly Notices of the Royal Astronomical Society


We present the results of a Keck/DEIMOS survey of Ultra Compact 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 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)×108 M⊙, 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 dE, with this progenitor dE having MB≈−16 mag and mass ∼109 M⊙.


This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2014 Aaron Romanowsky. Published by Oxford University Press on behalf of Monthly Notices of the Royal Astronomical Society . All rights reserved.