Oct 17, Non-Equilibrium Ionization Orly Gnat (Caltech) with Amiel Sternberg (Tel-Aviv University) Gnat & Sternberg 2007, ApJS, 168, 213 in Post-Shock Cooling Layersin Metal Ion Absorbers Gnat & Sternberg 2008, ApJ submitted

Oct 17, Non–Equilibrium Radiative Cooling Cooling is faster than recombination (t c <<t r ) Gas stays “over-ionized” Modified ionization affects cooling rates: for over-ionized gas cooling is suppressed Cooling rate depends on metallicity More metals ⇒ faster cooling ⇒ further out of equilibrium ApJS 168, 213

Oct 17, Numerical Computation Cooling from CIE at T>5x10 6 K. Follow time-dependent ionization dx i /dt=… ~ The energy equation (Cooling) dT/dt=… Step 1: No Photoionization dx i /dT independent of density …But depends on metallicity HHe CNO NeMg SiSFe ApJS 168, 213

Oct 17, Results: Ionization - Hydrogen Temperature (K) Recombination Lag time EquilibriumNon-Equilibrium ApJS 168, 213

Oct 17, Results: Ionization - Carbon Temperature (K) EquilibriumNon-Equilibrium ApJS 168, 213

Oct 17, Results: CIE Cooling Bremsstrahlung Metal Line Cooling He Cooling Hydrogen Cooling (Lya)  eq (erg cm 3 s -1 ) Temperature (K) Z = 2 Z = 1 Z = Z = Z = cooling efficiency

Oct 17, Results: Non-Equilibrium Cooling Equilibrium Non-Equilibrium

Oct 17, Local Metal-Ion Absorbers Turbulent Mixing Layers Conductive Interfaces Cooling Flows Shock Ionization log ( N V / O VI ) log ( C IV / O VI ) Fox et al ApJ 630, 332 ApJS 168, 213

Oct 17, High Velocity Metal Absorbers Fox et al ApJ, 630, 332

Oct 17, Time-Dependent Cooling - Summary Equilibrium and Non-Equilibrium Ionization States & Cooling Efficiencies of H, He, C, N, O, Ne, Mg, Si, S, & Fe, For 10 4 < T < 10 8 K and < Z < 2 solar. Isochoric / Isobaric – conditions & results. Impact of Self Radiation. ApJS 168, 213

Oct 17, Step 2: Steady Flows of Cooling Gas Integrated metal-ion cooling columns in steady flows of cooling gas

Oct 17, Post Shock Cooling Layers gas Pre-shockPost-shock T(x) shock Radiative transfer ⇒ Photoionization, heating Ionization: Auger Precursor Dynamics

Oct 17, Post-Shock Cooling Layers Two extremes: –No B field - explicitly follow Rankine-Hugoniot continuity eqns: Mass Momentum Energy Nearly isobaric flow: P ∞ = 4/3 P 0 –Strong B field - isochoric evolution.

Oct 17, Post-Shock Cooling: Shock Structure T s =5x10 6 K Z=0.1 n H =0.1cm -3 (Photoionized) Radiative Precursor High-T Radiative Zone Non-eq Cooling Zone The Photo- absorption Zone

Oct 17, Post-Shock Cooling: Shock Structure Shock temperature Magnetic field Gas Metallicity

Oct 17, Post-Shock Cooling: Emitted Radiation

Oct 17, Post-Shock Cooling: Column Densities

Oct 17, Gnat & Sternberg 2008 Shock Structure, Profiles, Scaling Relations Ion Fractions Cooling and Heating Integrated Column Densities Columns in Precursors Thank you !

Oct 17,

Oct 17, Introduction – add Xray obs too? UV & X-ray absorption line spectroscopy - Local High-Velocity Metal Absorbers: Si II, S II, C II, Si III, S III, Si IV, C IV, N V, O VI (E.g. Sembach et al. 1999, 2000, 2002, 2003; Murphy et al. 2000; Wakker et al. 2003; Collins et al. 2004; Fox et al. 2004, 2005, 2006) K Gas in Galactic Corona / WHIM: Si III, Si IV, C IV, N V, O VI, O VII, O VIII, Ne VIII, Ne IX (E.g. Collins et al. 2005; Fang et al. 2006; Tripp et al. 2000; Shull et al. 2004; Nicastro et al. 2005; Savage et al. 2005)