Brought to Light II: Revealing the Origins of Cloaked Spiral Features in
  Cluster Passive Dwarf Galaxies
  In our companion paper (Brought to Light I: Michea et al. 2021), 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 R$_{\rm{eff}}$. 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 (V$_{\rm{peak}}/\sigma_0 \sim 3$), 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 which 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
(r$_{\rm{peri}}<0.25$r$_{\rm{vir}}$) 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.
