Brought to Light. II. Revealing the Origins of Cloaked Spiral Features in Cluster Passive Dwarf Galaxies

Rory Smith*, Josefina Michea, Anna Pasquali, Paula Calderón-Castillo, Katarina Kraljic, Sanjaya Paudel, Thorsten Lisker, Jihye Shin, Jongwan Ko, Reynier F. Peletier, Eva K. Grebel

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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In our companion paper (Brought to Light I: Michea et al.), we reveal spectacular spiral-galaxy-like features in deep optical imaging of nine Virgo early-type dwarf galaxies, hidden beneath a dominating smooth stellar disk. Using a new combination of approaches, we find that bar- and spiral-like features contribute 2.2%-6.4% of the total flux within 2 Reff. In this study, we conduct high-resolution simulations of cluster harassment of passive dwarf galaxies. Following close pericenter passages of the cluster core, tidal triggering generates features in our model disks that bear a striking resemblance to the observed features. However, we find the disks must be highly rotationally supported (Vpeak0 ∼ 3), much higher than typically observed. We propose that some early-type dwarfs may contain a few percent of their mass in a cold, thin disk that is buried in the light of a hot, diffuse disk and only revealed when they undergo tidal triggering. The red optical colors of our sample do not indicate any recent significant star formation, and our simulations show that very plunging pericenter passages (rperi < 0.25rvir) are required for tidal triggering. Thus, many cluster early-type dwarfs with less-plunging orbits may host a yet-undetected cold stellar disk component. We discuss possible origin scenarios and consider why similar-mass star-forming galaxies in the field are significantly more thin-disk dominated than in our cluster sample.
Original languageEnglish
Article number149
Number of pages15
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 1-May-2021


  • Galaxy clusters
  • Galaxy disks
  • Galaxy dynamics
  • Galaxy dark matter halos
  • Galaxy environments
  • Galaxy encounters
  • N-body simulations
  • Dwarf galaxies
  • Galaxy stellar disks
  • 584
  • 589
  • 591
  • 1880
  • 2029
  • 592
  • 1083
  • 416
  • 1594
  • Astrophysics - Astrophysics of Galaxies


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