The Evolution of The Evolution of Intracluster LightIntracluster LightCraig RudickCraig RudickDepartment of AstronomyDepartment of AstronomyCase Western Reserve UniversityCase Western Reserve University

CollaboratorsCollaborators Chris MihosChris Mihos Cameron McBride (now at U. of Cameron McBride (now at U. of

Pittsburgh)Pittsburgh) Andrew Schechtman-Rook (now at Andrew Schechtman-Rook (now at

U. of Wisconsin)U. of Wisconsin)

All Images and Figures from Rudick, Mihos, & All Images and Figures from Rudick, Mihos, & Mcbride, 2006, ApJ, 648, 936Mcbride, 2006, ApJ, 648, 936

OutlineOutline What is ICL? – Thanks Chris!What is ICL? – Thanks Chris! Simulating ICLSimulating ICL Simulated ObservationsSimulated Observations

Simulating ClustersSimulating Clusters Start with a Start with a CDM, dark matter only CDM, dark matter only

cosmological N-body simulationcosmological N-body simulation At z=0 identify massive clustersAt z=0 identify massive clusters Trace cluster particles back to z=2Trace cluster particles back to z=2 Populate DM halos with hi-res Populate DM halos with hi-res

luminous galaxies modelsluminous galaxies models Resimulate to z=0Resimulate to z=0

Simulated Simulated ObservationsObservations

Discrete particles are smoothed Discrete particles are smoothed using an adaptive Gaussian using an adaptive Gaussian smoothing kernelsmoothing kernel

Apply a global mass-to-light ratioApply a global mass-to-light ratio– M/L = 5 (solar units) in VM/L = 5 (solar units) in V– No star formation, stellar evolution, No star formation, stellar evolution,

surface brightness dimming, etc.surface brightness dimming, etc.– Observing dynamical state of Observing dynamical state of

clusters as they would appear at z=0clusters as they would appear at z=0– All evolution is due to gravitational All evolution is due to gravitational

dynamics!dynamics!

Presented in Presented in TechnicolorTechnicolor 3 clusters3 clusters

– ~10~101414 solar solar massesmasses

– From z=2 to From z=2 to z=0z=0

– Taken from Taken from same same cosmologycosmology

Defining ICLDefining ICL Previously used definitions:Previously used definitions:

– Theory: unbound particles (stars)Theory: unbound particles (stars) Unobservable in broadband imagingUnobservable in broadband imaging

– Observation: excess over galactic profilesObservation: excess over galactic profiles Model dependent, not universally applicableModel dependent, not universally applicable

We define ICL as luminosity fainter We define ICL as luminosity fainter than than VV of 26.5 mag/sq. arcsec of 26.5 mag/sq. arcsec– Well-defined observableWell-defined observable– Radius at which ICL has unique morphologyRadius at which ICL has unique morphology– Holmberg RadiusHolmberg Radius

ICL Luminosity with ICL Luminosity with TimeTime The fraction of The fraction of

luminosity at ICL luminosity at ICL surface brightness surface brightness tends to increases tends to increases with timewith time

Increases are very Increases are very stochastic and stochastic and non-uniformnon-uniform

Each cluster has a Each cluster has a unique ICL historyunique ICL history

Changes in ICL Changes in ICL LuminosityLuminosity Fractional change in Fractional change in

luminosity per unit luminosity per unit timetime

ICL luminosity ICL luminosity increases tend to increases tend to come in short, come in short, discrete eventsdiscrete events

Increases in ICL Increases in ICL luminosity are highly luminosity are highly correlated with group correlated with group accretion eventsaccretion events

Cluster 2Cluster 2 Small group crashes through Small group crashes through

large central group from large central group from bottom left to top rightbottom left to top right– ICL increase coincides with ICL increase coincides with

galaxy exiting centergalaxy exiting center

ICL KinematicsICL Kinematics

ICL kinematics can be traced using ICL kinematics can be traced using PNe velocitiesPNe velocities

Work in progress!Work in progress!

Mean Velocity Velocity Dispersion

ConclusionsConclusions ICL luminosity tends to increase ICL luminosity tends to increase

with dynamical timewith dynamical time ICL luminosity increases are ICL luminosity increases are

strongly correlated with group strongly correlated with group accretion eventsaccretion events

ICL features are tracers of ICL features are tracers of cluster’s evolutionary historycluster’s evolutionary history