Non-Equilibrium Ionization
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Oct 17, 2008 1 Non-Equilibrium Ionization Orly Gnat (Caltech) with Amiel Sternberg (Tel-Aviv University) Gnat & Sternberg 2007, ApJS, 168, 213 in Post-Shock Cooling Layers in Metal Ion Absorbers and Gnat & Sternberg 2008, ApJ submitted
description
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. - PowerPoint PPT Presentation
Transcript of Non-Equilibrium Ionization
Oct 17, 2008 1
Non-Equilibrium Ionization
Orly Gnat(Caltech)
with Amiel Sternberg(Tel-Aviv University)
Gnat & Sternberg 2007, ApJS, 168, 213
in Post-Shock Cooling Layers
in Metal Ion Absorbers and
Gnat & Sternberg 2008, ApJ submitted
Oct 17, 2008 2
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 metallicity
More metals ⇒ faster cooling ⇒
further out of equilibrium
ApJS 168, 213
Oct 17, 2008 3
Numerical Computation• Cooling from CIE at T>5x106K.• Follow time-dependent ionization
dxi/dt=…
~
• The energy equation (Cooling) dT/dt=…• Step 1: No Photoionization• dxi/dT independent of density …But depends on metallicity
H HeC N O
Ne MgSi S Fe
ApJS 168, 213
Oct 17, 2008 4
Results: Ionization - Hydrogen
104 105 104 105 106
Temperature (K) Temperature (K)106
100
10-1
10-2
Recombination Lag
time
Equilibrium Non-Equilibrium
ApJS 168, 213
Oct 17, 2008 5
Results: Ionization - Carbon
104 105 104 105 106
Temperature (K) Temperature (K)106
100
10-1
10-2
Equilibrium Non-Equilibrium
ApJS 168, 213
Oct 17, 2008 6
Results: CIE Cooling
Bremsstrahlung
Metal LineCooling
He Cooling
10-21
10-22
10-23
10-24
H Lya
eq
(
erg
cm
3 s
-
1)
104 105 106 107 108
Temperature (K)
Z = 2Z = 1Z = 10-1
Z = 10-2
Z = 10-3
coo
lin
g e
ffic
ien
cy
Oct 17, 2008 7
Results: Non-Equilibrium Cooling
Equilibrium
Non-Equilibrium
Oct 17, 2008 8
Local Metal-Ion Absorbers
Turbulent
Mixing
Layers
Conductive
Interfaces
Co
oli
ng
Flo
ws
Sh
oc
kIo
niz
ati
on
log ( NV / OVI )
log
( C
IV /
OV
I )
Fox et al. 2005ApJ 630, 332
ApJS 168, 213
Oct 17, 2008 9
High Velocity Metal Absorbers
Fox et al. 2005ApJ, 630, 332
Oct 17, 2008 10
Time-Dependent Cooling - Summary• Equilibrium and Non-Equilibrium
Ionization 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
Oct 17, 2008 11
Step 2: Steady Flows of Cooling Gas
• Integrated metal-ioncooling columnsin steady flows of cooling gas
Oct 17, 2008 12
Post Shock Cooling Layers
gas
Pre-shock Post-shock
<— upstream downstream —>
T(x)
shock
• Radiative transfer ⇒ Photoionization, heating
• Ionization: Auger• Precursor
• Dynamics
Oct 17, 2008 13
Post-Shock Cooling Layers
• Two extremes:– No B field - explicitly follow
Rankine-Hugoniot continuity eqns:MassMomentumEnergy
Nearly isobaric flow: P∞ = 4/3 P0
– Strong B field - isochoric evolution.
)(v),(,)(,)( ttTtPt
Oct 17, 2008 14
Post-Shock Cooling: Shock Structure
Ts=5x106K
Z=0.1nH=0.1cm-3(P
hoto
ion
ized
) R
ad
iati
ve P
recu
rsor
High-TRadiative
Zone
Non-eqCoolingZone
The Photo-absorption
Zone
Oct 17, 2008 15
Post-Shock Cooling: Shock Structure
Shock temperature
Magneticfield Gas
Metallicity
Oct 17, 2008 16
Post-Shock Cooling: Emitted Radiation
Oct 17, 2008 17
Post-Shock Cooling: Column Densities
Oct 17, 2008 18
Gnat & Sternberg 2008
• Shock Structure, Profiles, Scaling Relations
• Ion Fractions• Cooling and Heating• Integrated Column Densities• Columns in Precursors
Thank you !
