1. Oct 17, 2008 0 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

2. Oct 17, 2008 1 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

3. Oct 17, 2008 2 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

4. Oct 17, 2008 3 Results: Ionization - Hydrogen 10 4 10 5 10 4 10 5 10 6 Temperature (K) 10 6 10 0 10 -1 10 -2 Recombination Lag time EquilibriumNon-Equilibrium ApJS 168, 213

5. Oct 17, 2008 4 Results: Ionization - Carbon 10 4 10 5 10 4 10 5 10 6 Temperature (K) 10 6 10 0 10 -1 10 -2 EquilibriumNon-Equilibrium ApJS 168, 213

6. Oct 17, 2008 5 Results: CIE Cooling Bremsstrahlung Metal Line Cooling He Cooling 10 -21 10 -22 10 -23 10 -24 Hydrogen Cooling (Lya)  eq (erg cm 3 s -1 ) 10 4 10 5 10 6 10 7 10 8 Temperature (K) Z = 2 Z = 1 Z = 10 -1 Z = 10 -2 Z = 10 -3 cooling efficiency

7. Oct 17, 2008 6 Results: Non-Equilibrium Cooling Equilibrium Non-Equilibrium

8. Oct 17, 2008 7 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. 2005 ApJ 630, 332 ApJS 168, 213

9. Oct 17, 2008 8 High Velocity Metal Absorbers Fox et al. 2005 ApJ, 630, 332

10. Oct 17, 2008 9 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 10 -3 < Z < 2 solar. Isochoric / Isobaric – conditions & results. Impact of Self Radiation. http://wise-obs.tau.ac.il/~orlyg/cooling/ ApJS 168, 213

11. Oct 17, 2008 10 Step 2: Steady Flows of Cooling Gas Integrated metal-ion cooling columns in steady flows of cooling gas

12. Oct 17, 2008 11 Post Shock Cooling Layers gas Pre-shockPost-shock T(x) shock Radiative transfer ⇒ Photoionization, heating Ionization: Auger Precursor Dynamics

13. Oct 17, 2008 12 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.

14. Oct 17, 2008 13 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

15. Oct 17, 2008 14 Post-Shock Cooling: Shock Structure Shock temperature Magnetic field Gas Metallicity

16. Oct 17, 2008 15 Post-Shock Cooling: Emitted Radiation

17. Oct 17, 2008 16 Post-Shock Cooling: Column Densities

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

19. Oct 17, 2008 18

20. Oct 17, 2008 19 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) 10 5 -10 7 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)