Metal Absorption in Conductively Evaporating Clouds

Einstein Fellows Symposium 10/27/20091

Orly Gnat, CaltechIn 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 AbsorbersSembach 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

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Ionization time > heating time?

Conductive Evaporation

hot

warm

heat flow

cloud evaporates

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Classic diffuse evaporation (Spitzer)

Saturated evaporation

Saturation parameter

Conductive Evaporation

TTTq ecl /

TTcq essat /5 3

PRT 3HIM

0

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Energy Conservation:

Dalton & Balbus 1993:

Conductive Evaporation

qnncvv

222 52

Bulk Kinetic Energy

Internal Energy +PdV work

RadiativeLosses & Gain

Inward Heat Flux

qvc

25 2

satcl

111qqq

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

4.015.0

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

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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

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Example: compact, high-P cloud

x6 dex in OVI

x1 dex in CIV

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High OVI Columns in Evaporating Clouds?

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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

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Fox et al. 2005

Equilibrium? TurbulentMixingLayers

ConductiveInterfaces

Coo

ling

Flow

s

Shoc

kIo

niza

tion

log ( NV / OVI )

log

( CIV

/ O

VI )

Fox et al. 2005ApJ 630, 332

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Photoionization

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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

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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

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Cowie & McKee 1977McKee & Cowie 1977Ballet, Arnaud & Rothenflug 1986Boehringer & Hartquist 1987Slavin 1989Slavin & Cox 1992Dalton & Balbus 1993Shelton 1998Smith & Cox 2001

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