Implications for the origin of dwarf early-type galaxies: a detailed look at the isolated rotating dwarf early-type dwarf galaxy LEDA 2108986 (CG 611), ramifications for the Fundamental Plane's (S_K)2 kinematic scaling and the spin-ellipticity diagram

Alister W. Graham, Joachim Janz, Samantha J. Penny, Igor V. Chilingarian, Bogdan C. Ciambur, Duncan A. Forbes, Roger L. Davies

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Abstract

Selected from a sample of nine, isolated, dwarf early-type galaxies (ETGs) having the same range of kinematic properties as dwarf ETGs in clusters, we use CG 611 (LEDA 2108986) to address the Nature versus Nurture debate regarding the formation of dwarf ETGs. The presence of faint disk structures and rotation within some cluster dwarf ETGs has often been heralded as evidence that they were once late-type spiral or dwarf irregular galaxies prior to experiencing a cluster-induced transformation into an ETG. However, CG 611 also contains significant stellar rotation (≈20 km s-1) over its inner half light radius, (Re,maj = 0.71 kpc), and its stellar structure and kinematics resemble those of cluster ETGs. In addition to hosting a faint young nuclear spiral within a possible intermediate-scale stellar disk, CG 611 has accreted an intermediate-scale, counter-rotating gas disk. It is therefore apparent that dwarf ETGs can be built by accretion events, as opposed to disk-stripping scenarios. We go on to discuss how both dwarf and ordinary ETGs with intermediate-scale disks, whether under (de)construction or not, are not fully represented by the kinematic scaling S0.5=√0.5 Vrot2 + σ2 }, and we also introduce a modified spin-ellipticity diagram, λ(R)-ε(R), with the potential to track galaxies with such disks.
Original languageEnglish
JournalThe Astrophysical Journal
Volume840
Issue number2
DOIs
Publication statusPublished - 8 May 2017

Keywords

  • astro-ph.GA
  • galaxies: dwarft
  • galaxies: evolution
  • galaxies: formation
  • galaxies: individual (CG 611)
  • galaxies: kinematics and dynamics
  • galaxies: structure

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