The Properties of Radio Relics in Cosmological Simulations Eric Hallman - Univ. of Colorado, NSF Fellow Sam Skillman - Univ. of Colorado, LANL Brian O’Shea - LANL, Michigan State University Jack Burns - Univ. of Colorado Michael Norman - UCSD Giantucci et al 2008 (A521) Juett et al 2008 (A13) Bagchi et al 2006, (A3376) Outline Motivation for Including Cosmic Ray Acceleration in Cosmological Simulations Shock Identification & Method of Calculating CR Dissipation Rate Merger shock radio relics in numerical AMR Enzo simulations Motivation Musings Thermalization, effects on offsetting radiative cooling Radio Observations constrain CRe population, B-fields Mass Estimates of Clusters Can we trust hydrostatic equilibrium? Are CR protons dynamically important? Dynamical state indicators? Radio Observations are a strong constraint on models of the ICM Shocks are responsible for a large part of the heating in structure formation. Specifically, the WHIM is created by shock-heating. If cosmic rays make up a large fraction of the pressure, they could have dynamical effects Could shocks be the source for high energy cosmic rays that are being observed by Pierre Auger? Probably not, but they might be re-accelerating. Shock-Finding in Enzo AMR Where do we introduce CRs? Previous studies used coordinate-split analysis Under-predicts Temperature Jump We allow for any orientation of the shock astro-ph/0806.1522 Results in a systematic shift to higher M Numerical Results of DSA Simulations How do we calculate energy dissipated into CRs? Kang & Jones (2002, 2007) Two Models With and Without Pre-existing CRs (30% Pressure) Cosmic Rays Heating - With CRs Heating: R-H Jump Conditions Cosmic Rays Heating - With CRs Fraction of Incoming Kinetic Energy Heating: R-H Jump Conditions We use the results of 1D nonlinear DSA simulations that calculate the fractional energy deposition into heating and the acceleration of cosmic rays The difference in the efficiencies is due to the difficulty of accelerating particles from a Maxwellian distribution to a power law distribution. If we already have a population of CRs, the kinetic energy will go straight into those. Mach Density CRs Temperature So now we want to take a look at the various quantities. Split these into four images if possible. Might be a pain in the ass. CR Energy Dissipation in Clusters Initial Results 128 Mpc box 15.6 kpc peak resolution Adiabatic 0< z <1.0 clusters Simulated Radio Relics Sort for images where extended CR Rate(outside 200 h^-1 kpc) is high (ECR, extended/ECR, total ~ 0.9-1.0) Distribution as F(M, z) About 15-20% have obvious merger shocks outside 200 kpc radius What are we doing to address these? Track CR proton pressure as simulation runs When RC is included, does CR pressure help offset? Just at shocks? Injected by AGN? Follow CRe momentum distribution (acceleration and losses, advection) to get realistic synth synchrotron obs Future: use MHD Enzo for all of this! Questions Are relics universal in disturbed systems? Can we find them if we go deeper, longer wavelengths? Can simulations reproduce radio halos? Are CR protons an important pressure component? Can we identify virial shocks in the radio? Method Conclusions AMR, New Algorithm, changes shock M distribution Relic morphology nicely reproduced by merger shocks No apparent redshift trend, mass trend yet Radio Relics are good diagnostic of cluster ICM B-fields, CR population, shock strengths 15-20% of simulated clusters have obvious merger relics Working on including CR pressure, CRe distribution “on the fly” We will generate a luminosity function for relics in radio/X-ray Selecting for Merger Shock Relic Sources Take projections of CR Energy Dissipation Rate Visually check Radial Profiles Density Temperature Mach Number CR Fraction Most energy is dissipated at internal shocks, but highest CR fraction is at the virial radius or greater. Direct result of CR efficiency of acceleration. Shocks “On-the-Fly” Identify shocks using same criteria Calculate CR acceleration and passively follow CRs advecting with the flow. Future: Back effect of CRs on the hydrodynamics 1 10 100 Matt Turk (Stanford/KIPAC) http://yt.enzotools.org/ What do we really want to know? How are CRs deposited/accelerated in the ICM? What is the dynamical/thermal impact on the ICM? Are our models consistent with radio/X-ray observations of the cluster gas? How do we correctly generate/evolve a CR population (electrons and protons) in simulations? How can we use relics as ICM diagnostics? What are the necessary future steps? Astrophysics Apply to Non-Adiabatic Physics Simulations Track CR evolution (injection at AGNs, acceleration at shocks, losses) Pressure Contribution of CR protons? Computational Include Cosmic Rays in Pressure Calculation Magnetic Fields (MHD Enzo) Synthetic Observations Realistic Synchotron emission Synthetic X-ray obs (cool cores, heating) Consistent with X-ray/radio obs? Coordinate Effects astro-ph/0806.1522 Results from the Santa Fe Light Cone Simulation Shock Conditions Converging Gas Entropy increases across shockwave Rankine-Hugoniot Jump Conditions Figure out what cold fronts are!