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The Evolution of Intracluster Light

The Evolution of Intracluster Light. Craig Rudick Department of Astronomy Case Western Reserve University. Collaborators. Chris Mihos Cameron McBride (now at U. of Pittsburgh) Andrew Schechtman-Rook (now at U. of Wisconsin)

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The Evolution of Intracluster Light

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  1. The Evolution of Intracluster Light Craig Rudick Department of Astronomy Case Western Reserve University

  2. Collaborators • Chris Mihos • Cameron McBride (now at U. of Pittsburgh) • Andrew Schechtman-Rook (now at U. of Wisconsin) All Images and Figures from Rudick, Mihos, & Mcbride, 2006, ApJ, 648, 936

  3. Outline • What is ICL? – Thanks Chris! • Simulating ICL • Simulated Observations

  4. Simulating Clusters • Start with a LCDM, dark matter only cosmological N-body simulation • At z=0 identify massive clusters • Trace cluster particles back to z=2 • Populate DM halos with hi-res luminous galaxies models • Resimulate to z=0

  5. Simulated Observations • Discrete particles are smoothed using an adaptive Gaussian smoothing kernel • Apply a global mass-to-light ratio • M/L = 5 (solar units) in V • No star formation, stellar evolution, surface brightness dimming, etc. • Observing dynamical state of clusters as they would appear at z=0 • All evolution is due to gravitational dynamics!

  6. Presented in Technicolor • 3 clusters • ~1014 solar masses • From z=2 to z=0 • Taken from same cosmology

  7. Defining ICL • Previously used definitions: • Theory: unbound particles (stars) • Unobservable in broadband imaging • Observation: excess over galactic profiles • Model dependent, not universally applicable • We define ICL as luminosity fainter than mV of 26.5 mag/sq. arcsec • Well-defined observable • Radius at which ICL has unique morphology • Holmberg Radius

  8. ICL Luminosity with Time • The fraction of luminosity at ICL surface brightness tends to increases with time • Increases are very stochastic and non-uniform • Each cluster has a unique ICL history

  9. Changes in ICL Luminosity • Fractional change in luminosity per unit time • ICL luminosity increases tend to come in short, discrete events • Increases in ICL luminosity are highly correlated with group accretion events

  10. Cluster 2 • Small group crashes through large central group from bottom left to top right • ICL increase coincides with galaxy exiting center

  11. ICL Kinematics • ICL kinematics can be traced using PNe velocities • Work in progress! Velocity Dispersion Mean Velocity

  12. Conclusions • ICL luminosity tends to increase with dynamical time • ICL luminosity increases are strongly correlated with group accretion events • ICL features are tracers of cluster’s evolutionary history

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