The Effect of Ram-Pressure Stripping on Dwarf Galaxies
  Ram-pressure stripping (RPS) is a well observed phenomenon of massive spiral
galaxies passing through the hot intra-cluster medium (ICM) of galaxy clusters.
For dwarf galaxies (DGs) within a cluster, the transformation from gaseous to
gas-poor systems by RPS is not easily observed and must happen in the outskirts
of clusters. In a few objects in close by galaxy clusters and the field, RPS
has been observed. Since cluster early-type DGs also show a large variety of
internal structures (unexpected central gas reservoirs, blue stellar cores,
composite radial stellar profiles), we aim in this study to investigate how ram
pressure (RP) affects the interstellar gas content and therefore the
star-formation (SF) activity. Using a series of numerical simulations, we
quantify the dependence of the stripped-off gas on the velocity of the
infalling DGs and on the ambient ICM density. We demonstrated that SF can be
either suppressed or triggered by RP depending on the ICM density and the DGs
mass. Under some conditions, RP can compress the gas, so that it is
unexpectedly retained in the central DG region and forms stars. When gas clouds
are still bound against stripping but lifted from a thin disk and fall back,
their new stars form an ellipsoidal (young) stellar population already with a
larger velocity dispersion without the necessity of harassment. Most
spectacularly, star clusters can form downstream in stripped-off massive gas
clouds in the case of strong RP. We compare our results to observations.
