Non-Equilibrium Ionization
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Non-Equilibrium Ionization. in Metal Ion Absorbers and. in Post-Shock Cooling Layers. Gnat & Sternberg 2007, ApJS, 168, 213. Gnat & Sternberg 2008, ApJ submitted. Orly Gnat (Caltech) with Amiel Sternberg (Tel-Aviv University). Non–Equilibrium Radiative Cooling.

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Non-Equilibrium Ionization

in Metal Ion Absorbers and

in Post-Shock Cooling Layers

Gnat & Sternberg 2007, ApJS, 168, 213

Gnat & Sternberg 2008, ApJ submitted

Orly Gnat

(Caltech)

with Amiel Sternberg

(Tel-Aviv University)


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Non–Equilibrium Radiative Cooling

  • Cooling is faster than recombination(tc<<tr)

  • Gas stays “over-ionized”

  • Modified ionization affects cooling rates:for over-ionized gas cooling is suppressed

  • Cooling rate depends on metallicityMore metals ⇒ faster cooling ⇒

    further out of equilibrium

ApJS 168, 213


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H

He

C

N

O

Ne

Mg

Si

S

Fe

Numerical Computation

  • Cooling from CIE at T>5x106K.

  • Follow time-dependent ionizationdxi/dt=…

~

  • The energy equation (Cooling) dT/dt=…

  • Step 1: No Photoionization

  • dxi/dT independent of density

  • …But depends on metallicity

ApJS 168, 213


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time

Results: Ionization - Hydrogen

Equilibrium

Non-Equilibrium

100

10-1

10-2

104

105

106

104

105

106

Temperature (K)

Temperature (K)

Recombination Lag

ApJS 168, 213


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Results: Ionization - Carbon

Equilibrium

Non-Equilibrium

100

10-1

10-2

104

105

106

104

105

106

Temperature (K)

Temperature (K)

ApJS 168, 213


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Results: CIE Cooling

Metal Line

Cooling

Z = 2

Z = 1

Z = 10-1

Z = 10-2

Z = 10-3

10-21

10-22

H Lya

Leq (erg cm3 s-1)

cooling efficiency

He Cooling

10-23

Bremsstrahlung

10-24

104

105

106

107

108

Temperature (K)


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Equilibrium

Non-Equilibrium

Results: Non-Equilibrium Cooling


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Fox et al. 2005

ApJ 630, 332

Turbulent

Mixing

Layers

log ( CIV / OVI )

Shock

Ionization

Conductive

Interfaces

Cooling

Flows

log ( NV / OVI )

Local Metal-Ion Absorbers

ApJS 168, 213


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High Velocity Metal Absorbers

Fox et al. 2005

ApJ, 630, 332


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Time-Dependent Cooling - Summary

  • Equilibrium and Non-EquilibriumIonization States & Cooling Efficiencies ofH, He, C, N, O, Ne, Mg, Si, S, & Fe,For 104 < T < 108 Kand 10-3 < Z < 2 solar.

  • Isochoric / Isobaric – conditions & results.

  • Impact of Self Radiation.

    http://wise-obs.tau.ac.il/~orlyg/cooling/

ApJS 168, 213


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Step 2: Steady Flows of Cooling Gas

  • Integrated metal-ioncooling columnsin steady flows of cooling gas


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Post Shock Cooling Layers

  • Radiative transfer⇒ Photoionization, heating

  • Ionization: Auger

  • Precursor

  • Dynamics

shock

Pre-shock

Post-shock

gas

T(x)

<— upstream downstream —>


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Post-Shock Cooling Layers

  • Two extremes:

    • No B field - explicitly follow Rankine-Hugoniot continuity eqns:

      Mass

      Momentum

      Energy

      Nearly isobaric flow: P∞ = 4/3 P0

    • Strong B field - isochoric evolution.


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High-T

Radiative

Zone

Non-eq

Cooling

Zone

The Photo-

absorption

Zone

Post-Shock Cooling: Shock Structure

Ts=5x106K

Z=0.1

nH=0.1cm-3

(Photoionized) Radiative Precursor


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Post-Shock Cooling: Shock Structure

Magnetic

field

Gas

Metallicity

Shock temperature




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Gnat & Sternberg 2008

  • Shock Structure, Profiles, Scaling Relations

  • Ion Fractions

  • Cooling and Heating

  • Integrated Column Densities

  • Columns in Precursors

    Thank you !


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