ch+ and sh+ absorption spectroscopy with herschel:...
TRANSCRIPT
CH+ and SH+ absorption spectroscopy with Herschel: probingthe turbulent dissipation in the diffuse ISM.
B. Godard, E. Falgarone, G. Pineau des ForêtsM. Gerin, P. Lesaffre, F. Levrier
1 Quick overview of turbulence and its unkowns
2 The TDR (turbulent dissipation regions) model
3 Derive turbulence properties from molecular observations
Quick overview of turbulence 2/13
turbulent cascadeadvection force u · ∇udissipation forces
I friction ν∇2u
I compression 13ν∇[∇ · u]
I ambipolar diff. γin(ui − un)I magnetic diff. µ∇2b
transfer rate
ε = 2× 10−25 erg cm−3 s−1
Hennebelle & Falgarone (2012)
Quick overview of turbulence 3/13
intermittency
in space & timelocal dissipation ε = ε/fv
Frish (1995)
Moisy & Jimenez (2004)
unresolved questions
dissipative scales ?dissipative structure ?physical processes involved ?local rate of dissipation ?
The TDR (turbulent dissipation regions) model 4/13
dissipative phase
magnetized vorticesa2 = 4ν/l, uθmLagrangian approachnon-equilibrium chemistryturbulent heating processes
I viscous frictionI ion-neutral friction
relaxation phase
Eulerian approachno turbulent heating
courtesy of P. Hily-Blant
The TDR (turbulent dissipation regions) model 5/13
model parameters
• density nH
• shielding AV
• CR ionization ζ
• stretching a → l
• max rot. vel. uθm → uin
• transfer rate ε → NV
• lifetime τV → NR
The TDR (turbulent dissipation regions) model 6/13
Strategy to derive turbulent properties
% vortex
% relaxation% ambient0
0 0
100
100 100
% vortex
% relaxation% ambient0
0 0
100
100 100
CH+ SH+ CO HF CH
% vortex
% relaxation% ambient0
0 0
100
100 100
% vortex
% relaxation% ambient0
0 0
100
100 100
HCO+ C2H OH H2O H/H2
nH increases with increasing symbol sizeAV = 0.4, ζ = 3× 10−17 s−1
Turbulence properties from molecular observations 7/13
Large scale turbulent energy
1e+10
1e+11
1e+12
1e+13
1e+14
1e+15
1e+16
1e+20 1e+21 1e+22
N(C
H+ ) (
cm-2
)
NH tot (cm-2)
PDR models
nH = 10 cm-3
nH = 100 cm-3
visibleHerschel
1e+10
1e+11
1e+12
1e+13
1e+14
1e+15
1e+16
1e+20 1e+21 1e+22
N(C
H+ ) (
cm-2
)
NH tot (cm-2)
PDR models
nH = 10 cm-3
nH = 100 cm-3
N(CH+)local = 3×N(CH+)disk
N(CH+)NH
∝ ε n−2.2H A−0.32
V a−0.5
nH < 200 cm−3
15< ε
10−24 erg cm−3 s−1 < 5
IJ
I
I
II
I
II
I
I
I
I
C C+
CH CH+
CH2 CH+2
CH+3
γ
e−
γH2
H2
4640
H2
H2
γ
γ
2200H
H2
1760
e−
e−
Turbulence properties from molecular observations 7/13
Large scale turbulent energy
1e+10
1e+11
1e+12
1e+13
1e+14
1e+15
1e+16
1e+20 1e+21 1e+22
N(C
H+ ) (
cm-2
)
NH tot (cm-2)
TDR models
nH = 30 cm-3
nH = 100 cm-3
visibleHerschel
1e+10
1e+11
1e+12
1e+13
1e+14
1e+15
1e+16
1e+20 1e+21 1e+22
N(C
H+ ) (
cm-2
)
NH tot (cm-2)
TDR models
nH = 30 cm-3
nH = 100 cm-3
N(CH+)local = 3×N(CH+)disk
N(CH+)NH
∝ ε n−2.2H A−0.32
V a−0.5
nH < 200 cm−3
15< ε
10−24 erg cm−3 s−1 < 5
IJ
I
I
II
I
II
I
I
I
I
C C+
CH CH+
CH2 CH+2
CH+3
γ
e−
γH2
H2
4640
H2
H2
γ
γ
2200H
H2
1760
e−
e−
Turbulence properties from molecular observations 8/13
Ion-neutral drift in dissipative regions
10-3
10-2
10-1
100
101
10-9 10-8 10-7
N(S
H+ )/N
(CH
+ )
N(CH+)/NH
TDR, uem = 2 km s-1Godard et al. (2012)
2.5 6 uθm 6 3.5 km s−1
reproduces the correlationSH abundance reproduced(SOFIA-GREAT, Neufeld et al. 2012)
II
II
I
I
I
I
C+
CH+
CH+2
S+
SH+
SH+2
S
SH
H2
4640
H2
H2
9860
H2
8500
γ
γe−
e−
N(SH+)
N(CH+)∝ exp(−5220/Teff)
Teff = Tr +13µku2
in
independent of a and ε
Turbulence properties from molecular observations 8/13
Ion-neutral drift in dissipative regions
10-3
10-2
10-1
100
101
10-9 10-8 10-7
N(S
H+ )/N
(CH
+ )
N(CH+)/NH
TDR, uem = 3 km s-1Godard et al. (2012)
2.5 6 uθm 6 3.5 km s−1
reproduces the correlationSH abundance reproduced(SOFIA-GREAT, Neufeld et al. 2012)
II
II
I
I
I
I
C+
CH+
CH+2
S+
SH+
SH+2
S
SH
H2
4640
H2
H2
9860
H2
8500
γ
γe−
e−
N(SH+)
N(CH+)∝ exp(−5220/Teff)
Teff = Tr +13µku2
in
independent of a and ε
Turbulence properties from molecular observations 8/13
Ion-neutral drift in dissipative regions
10-3
10-2
10-1
100
101
10-9 10-8 10-7
N(S
H+ )/N
(CH
+ )
N(CH+)/NH
TDR, uem = 5 km s-1Godard et al. (2012)
2.5 6 uθm 6 3.5 km s−1
reproduces the correlationSH abundance reproduced(SOFIA-GREAT, Neufeld et al. 2012)
II
II
I
I
I
I
C+
CH+
CH+2
S+
SH+
SH+2
S
SH
H2
4640
H2
H2
9860
H2
8500
γ
γe−
e−
N(SH+)
N(CH+)∝ exp(−5220/Teff)
Teff = Tr +13µku2
in
independent of a and ε
Turbulence properties from molecular observations 8/13
Ion-neutral drift in dissipative regions
10-3
10-2
10-1
100
101
10-9 10-8 10-7
N(S
H+ )/N
(CH
+ )
N(CH+)/NH
TDR, uem = 3 km s-1Godard et al. (2012)
2.5 6 uθm 6 3.5 km s−1
reproduces the correlationSH abundance reproduced(SOFIA-GREAT, Neufeld et al. 2012)
II
II
I
I
I
I
C+
CH+
CH+2
S+
SH+
SH+2
S
SH
H2
4640
H2
H2
9860
H2
8500
γ
γe−
e−
N(SH+)
N(CH+)∝ exp(−5220/Teff)
Teff = Tr +13µku2
in
independent of a and ε
Turbulence properties from molecular observations 9/13
Turbulent dissipation timescale
106
107
108
109
1010
1011
1012
102 103 104 105
vorte
x co
lum
n de
nsity
(cm
-2)
time (yr)
CH
CH+
OHH2O
HCO+
CO
106
107
108
109
1010
1011
1012
102 103 104 105
vorte
x co
lum
n de
nsity
(cm
-2)
time (yr)
CH
CH+
OHH2O
HCO+
CO
• CO formation in TDR : CH+ 99K CH+3 → HCO+ → CO
• τR(CO) ∼ 100× τR(CH+) ∼ 100τR(HCO+)
• N(CO) ∝ τR/τV → 102 6 τV 6 103 yr
Turbulence properties from molecular observations 9/13
Turbulent dissipation timescale
106
107
108
109
1010
1011
1012
102 103 104 105
vorte
x co
lum
n de
nsity
(cm
-2)
time (yr)
CH
CH+
OHH2O
HCO+
CO
106
107
108
109
1010
1011
1012
102 103 104 105
vorte
x co
lum
n de
nsity
(cm
-2)
time (yr)
CH
CH+
OHH2O
HCO+
CO
1013
1014
1015
1016
1017
1011 1012 1013
N(C
O) (
cm-2
)
N(HCO+) (cm-2)
TDR, o = 104 yrLiszt Lucas (1998)
• CO formation in TDR : CH+ 99K CH+3 → HCO+ → CO
• τR(CO) ∼ 100× τR(CH+) ∼ 100τR(HCO+)
• N(CO) ∝ τR/τV → 102 6 τV 6 103 yr
Turbulence properties from molecular observations 9/13
Turbulent dissipation timescale
106
107
108
109
1010
1011
1012
102 103 104 105
vorte
x co
lum
n de
nsity
(cm
-2)
time (yr)
CH
CH+
OHH2O
HCO+
CO
106
107
108
109
1010
1011
1012
102 103 104 105
vorte
x co
lum
n de
nsity
(cm
-2)
time (yr)
CH
CH+
OHH2O
HCO+
CO
1013
1014
1015
1016
1017
1011 1012 1013
N(C
O) (
cm-2
)
N(HCO+) (cm-2)
TDR, o = 102 yrLiszt Lucas (1998)
• CO formation in TDR : CH+ 99K CH+3 → HCO+ → CO
• τR(CO) ∼ 100× τR(CH+) ∼ 100τR(HCO+)
• N(CO) ∝ τR/τV → 102 6 τV 6 103 yr
Turbulence properties from molecular observations 10/13
Stretching of turbulent dissipation regions
10-25
10-24
10-23
10-22
101 102 103 104 105 106
C+ c
oolin
g ra
te (e
rg c
m-3
s-1
)
time (yr)
AV = 0.1AV = 0.2AV = 0.4AV = 1.0
02468
10121416
0.0 0.5 1.0 1.5 2.0 2.5
I C+ (
10-6
erg
cm
-2 s
-1 s
r-1)
NH (mag)
PDR
Ingalls et al. (2002)
0 100 200 300 400 500
IFIR (10-6 erg cm-2 s-1 sr-1)
• under-emission during the dissipative burst ∼ 100 yr• over-emission during the relaxation period ∼ 104 yr
• 10−12 6 a 6 10−10 s−1 → 100 6 l 6 1000 AU
Turbulence properties from molecular observations 10/13
Stretching of turbulent dissipation regions
10-25
10-24
10-23
10-22
101 102 103 104 105 106
C+ c
oolin
g ra
te (e
rg c
m-3
s-1
)
time (yr)
AV = 0.1AV = 0.2AV = 0.4AV = 1.0
02468
10121416
0.0 0.5 1.0 1.5 2.0 2.5
I C+ (
10-6
erg
cm
-2 s
-1 s
r-1)
NH (mag)
TDR, a = 10-11 s-1
TDR, a = 10-10 s-1
Ingalls et al. (2002)
0 100 200 300 400 500
IFIR (10-6 erg cm-2 s-1 sr-1)
• under-emission during the dissipative burst ∼ 100 yr• over-emission during the relaxation period ∼ 104 yr• 10−12 6 a 6 10−10 s−1 → 100 6 l 6 1000 AU
Turbulence properties from molecular observations 11/13
Additional TDR predictions
Levrier et al. (2012)
1012
1013
1014
1015
1016
1020 1021 1022
N(C
O) (
cm-2
)
NH (cm-2) (assuming fH2 = 0.5)
TDR, AV = 0.02TDR, AV = 0.10TDR, AV = 0.20TDR, AV = 0.40TDR, AV = 0.60
Scheffer et al. (2008)
realistic fragmentation + PDR TDR
• N(CO)obs/N(CO)PDR > 10
• explains the bending ofN(CO) at N(H2) ∼ 2× 1020
• if complete fragment. no bending• if no fragment. strong bending
and N(CO) too small at small NH
Turbulence properties from molecular observations 12/13
Additional TDR predictions
1012
1013
1014
1015
1011 1012 1013
N(O
H) (
cm-2
)
N(HCO+) (cm-2)
PDR TDR
Lucas and Liszt (1996)
1012
1013
1014
1011 1012 1013
N(H
2O) (
cm-2
)
N(HCO+) (cm-2)
PDR TDR
Olofsson et al. (2010)
1012
1013
1014
1011 1012 1013
N(C
2H) (
cm-2
)
N(HCO+) (cm-2)
PDR
TDRLucas and Liszt (2000)
1013
1015
1017
1019
1021
0 1000 2000 3000
N(H
2)/g
j (cm
-2)
Energy (K)
PDR
TDR
Gry et al. (2002), Lacour et al. (2004)
Conclusions 13/13
Summary
properties of turbulent dissipationI CH+ / H → dissipation rate nH, ε
I SH+ / CH+ → ion-neutral decoupling nH, uθm = uinI C+(160µm) / FIR → stretching a→ l
I CO / HCO+ → timescale τV
agreement with other molecular tracersI CO / H2 → fragmented mediumI column densities of OH, H2O, C2H, CH, SH, and H?2I ... and their correlations
Future contributions
open issues
explain H2S abundances
interpret velocity profiles
ALMA perspectives
mapping the dissipative scales
turbulence in extragalactic media