Post on 19-Dec-2015
Einstein Fellows Symposium 10/27/20091
Orly Gnat, Caltech
In Collaboration with :
Amiel Sternberg, Chris McKee
Metal Absorption in Conductively
Evaporating Clouds
Einstein Fellows Symposium 10/27/20092
• UV observationsrevealed a population oflocal highly ionized absorbers
(Sembach et al. 1999, 2000, 2002, 2003; Murphy et al. 2000; Wakker et al. 2003;Collins et al. 2004, Fox et al. 2005, 2006…)
High Velocity Metal Absorbers
Sembach et al. 2003, ApJ, 146, 165S
Einstein Fellows Symposium 10/27/20093
Hydrostatic spherical gas cloudsembedded in dark matter minihalosphotoionized by “metagalactic” fieldpressure supported by an external hot medium
Consider –dwarf galaxy scale objectslower mass starless minihalo models for CHVC(Sternberg McKee & Wolfire)
Metal Absorbers as Photoionized Clouds
- Gnat & Sternberg 2004, ApJ, 608, 229
Einstein Fellows Symposium 10/27/20094
Ionization time > heating time?
Conductive Evaporation
hot
warm
heat flow
cloud evaporates
Einstein Fellows Symposium 10/27/20095
Classic diffuse evaporation (Spitzer)
Saturated evaporation
Saturation parameter
Conductive Evaporation
TTTq ecl /
TTcq essat /5 3
PR
T 3HIM0
Einstein Fellows Symposium 10/27/20096
Energy Conservation:
Dalton & Balbus 1993:
Conductive Evaporation
qnncvv
222 52
Bulk Kinetic Energy
Internal Energy +PdV work
RadiativeLosses & Gain
Inward Heat Flux
qvc
2
5 2
satcl
111
qqq
Einstein Fellows Symposium 10/27/20097
DB93 Temperature Profiles Solutions
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The Non-Radiative Approximation
McKee & Cowie 1977:equilibrium cooling, Z=1 solarcritical saturation parameter
Under-ionized, over-cooled non-equilibrium gas:
Z=0.1 solar
Z=1 solar• Under-ionized He+ cooling!
1.0~/03.00 s
4.0
15.0
0
0
Einstein Fellows Symposium 10/27/20099
H, He, C, N, O, Si, Sdx / dr =
Collisional ionization / rec.Photoionization
by metagalactic fieldRadiative recombinationsDielectronic recombinationsCharge exchange with H & H+
0.1 < P/kB < 104 cm-3 K1 pc < R < 100 kpc5 x 105 < T < 107 K
Cooling using Cloudy
Ionization
Einstein Fellows Symposium 10/27/200910
Under-Ionized,over-cooled gas
Non-Eq Ionization
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Non-Equilibrium Columns?
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For comparison with observations of metal ion absorbers
Focus on dwarf galaxy scale objects0.1 < P/kB < 50 cm-3 K1 < R < 7.5 kpcT = 1-2 x 106 K
Column density versus impact parameter
Metal Absorption Column Densities
Einstein Fellows Symposium 10/27/200913
Example: compact, high-P cloud
x6 dex in OVI
x1 dex in CIV
Einstein Fellows Symposium 10/27/200914
High OVI Columns in Evaporating Clouds?
Einstein Fellows Symposium 10/27/200915
SummaryNon-Equilibrium of H, He, C, N, O, Si, SNon-Radiative approximation: σ0>0.15 (Z=0.1)
σ0>0.4 (Z=1) Extension of photoionized models
for metal-ion absorbersConductive interfaces enhance formation of high
ionsStill too low to account for observed OVI columns
(~1014 cm-2)OVI limit of ~1013 cm-2 for evaporating clouds
Einstein Fellows Symposium 10/27/200916
Einstein Fellows Symposium 10/27/200917
Fox et al. 2005
Equilibrium? TurbulentMixingLayers
ConductiveInterfaces
Cooli
ng
Flo
ws
Sh
ock
Ion
izati
on
log ( NV / OVI )
log
( C
IV
/ O
VI )
Fox et al. 2005ApJ 630, 332
Einstein Fellows Symposium 10/27/200918
Photoionization
Einstein Fellows Symposium 10/27/200919
Absorption to Mrk509 & PKS2155-304
log column cm-2
C IV 1548.2 Å 13.5 - >14.20
N V 1238.8 Å <13.08 - <13.24
Si III 1012.5 Å 12.44 - 13.31
Si IV 1393.8 Å <12.33 - >13.44
S III 1190.2 Å <13.68 - <13.93
O VI 1031.9 Å 13.56 - 13.93
Einstein Fellows Symposium 10/27/200920
CHVC scale objects (Mvir~108Mo, P~50 cm-3 K)embedded in high-pressure Galactic Corona:ionization parameter too low.
Dwarf galaxy scale objects (Mvir~2x109Mo, P~0.1 cm-3 K):embedded in low pressure IGM:
Metal Absorbers as Photoionized Clouds
Einstein Fellows Symposium 10/27/200921
Local Cloud & Local bubbleISM clouds SNRsAGNGalaxy formation
Used in
Einstein Fellows Symposium 10/27/200922
Cowie & McKee 1977McKee & Cowie 1977Ballet, Arnaud & Rothenflug 1986Boehringer & Hartquist 1987Slavin 1989Slavin & Cox 1992Dalton & Balbus 1993Shelton 1998Smith & Cox 2001
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