Tidal Debris in Galaxy Clusters

Evolving views:
  • "Classical picture" of galaxy evolution in clusters: cluster potential plus ram pressure stripping dominate, while slow encounters & mergers are unlikely. 
  • "Hierarchical picture": galaxies are accreted in groups, where encounters are strong and slow.
Observational Data:

 Numerical Simulations:
(courtesy John Hibbard)
 (courtesy John Dubinski)
  • Ghigna etal (1999): mergers strong at z>1, shutoff in cluster core thereafter.
  • Gnedin (2003): significant activity in outskirts, merger rate 20-30% over lifetime of the cluster
How does the cluster environment affect tidal debris and stripping?

The effects of global tides:

Simple model: merging in a tidal field, but will apply to any tidal interaction.
  • Tidal debris stripped away, hard to detect (the ICL!)
  • Late infall of stripped material is limited -- disk rebuilding in clusters is curtailed. Merger/reaccretion models for cluster S0's may be problematic.
  • Gaseous tails will be very low density and patchy. Now factor in ram pressure stripping.

Compare:



Cluster Model
rs 0.3 Mpc
r 200 2 Mpc
M200 1015 Msun
rperi 0.5 Mpc
rapo 2.0 Mpc



Interactions in the group environment "prime the pump" for tidally stripping galaxies even at large cluster-centric distances: Unbound Fraction:
Cluster Spiral
 2%
Field Merger
 2%
Cluster Merger
 30%





"Group assisted" tidal stripping very efficient and very deep:
  • contribute lots of moderately high metallicity stars (and gas) to the intracluster environment.
  • possible concern for intracluster redgiant detections?