Line emission in shocks and PDR - Observatoire de Paris

Line emission from shocks
Sylvie Cabrit (Observatoire de Paris)
G. Pineau des Forêts, D. Flower, J. Le Bourlot (shock
models), C. Ceccarelli (CO and H 2
O predictions)
•Shocks in outflows: evidence for C-precursors (ISO)
•Water emission from shocks: need for Herschel
•Chemistry and internal structure: need for ALMA
and PDRs
M. Gérin and J. Le Bourlot
(Observatoire de Paris)
Dusty04 - Paris, October 2004

Magnetic molecular shocks
Low ionisation, magnetized
medium ion/neutral
decoupling Continuous
(C-type) « shock »
Magnetic precursor
Viscous J-type front
Long time-scales to reach
full C steady-state
t ~ 10 4 yrs x (10 4 cm-3/nH)
Young shocks combine C-
precursor + viscous J-front
(Chieze et al. 1998; Lesaffre et al.
2004)
« Age typical 1000 » yrs stationary : C+J structure C-shock nH
nH = 10 4 cm-3, Vs = 25 km/s B = 100µ G.
Dusty04 - Paris, October 2004

Evidence for C-precursors: H2 pure
rotational lines in molecular flows
H2 v=0-0 S(5) line flux (6’’ to 20’’ beams)
H2 v=0 excitation temperature
HH2 with ISOCAM (Lefloch et al. 2003)
Cabrit et al. 2003 (with SWS data from Wright et
al., Rosenthal et al.)
Dusty04 - Paris, October 2004

CO and H2O: The ISO-LWS view
LVG (Giannini et al. 2001):
Warm gas (200-2000 K)
Dense (3x10 4 -10 7 cm-3)
Compact (ff ~ 1% : typical
size 10’’)
L(CO + H2O) ~ outflow Lkin
Shocked gas ?
X(H2O)/X(CO)
3
1
0.3
0.1
C-shock models (Tgas
= Tmax)
X(H2O)/X(CO) increases with
temperature: mantle
desorption and O to H 2
O
conversion.
Dusty04 - Paris, October 2004

Shocks sampled by ISO-LWS:
of NGC 1333-IRS4
The example
(CO fluxes from Giannini et al. 2001)
High-J CO lines not very
discriminant; can be
fitted by various shock
models of age 1000 yrs:
Dense C
CJ
C
ff=0.017
ff=0.2
J
ff=1
Dusty04 - Paris, October 2004

Shocks sampled by ISO-LWS:
of NGC 1333-IRS4
The example
H2O lines very discriminant:
only dense C-shocks of low ff
can fit both 179µ m and 80µ m
(H2O fluxes from Giannini et al. 2001)
nH = 10 4 cm-3:
Pure J: Vs = 15 km/s, b=0.1 (ff = 1)
C+J: Vs = 25 km/s, b=1 (ff = 1)
Pure C: Vs = 50 km/s, b=1 (ff =
0.2)
nH = 10 5 cm-3:
Pure C: Vs = 25 km/s, b=1 (ff =
0.017)
Dusty04 - Paris, October 2004

The 557GHz ortho-H2O line
SWAS observations of molecular outflows: broad
wings shocked gas, but 2-3 times stronger than
expected from ISO-LWS (Benedettini et al. 2003)
Extended component, too cold for ISO
Estimated H 2
O abundance ~ 10 -6 if dominated by
cold swept-up CO (Neufeld et al. 2000)
lower than expected for shocks of V > 5 km/s…
ODIN observations of IRAS 16293 (Ristorcelli et al.
2004) : similar lobe size to ISO-LWS (120’’ vs 80’’).
Dusty04 - Paris, October 2004

Comparison of H2O(557GHz) and CO(3-2) in
the ODIN beam
CO(3-2)/1.5 (Lis
et al.)
CO(3-2)/H 2
O(557GHz)
H 2
O 557GHz
X(H 2
O)/X(CO)
-20 0 20 km/s
CO(3-2)/H 2
O ~ 1.5 in red wing, ~ 2.5 in blue wing
C-Shocks with Vs ~ 12-15 km/s (ff ~ 0.2 in 120’’ beam)
X(H 2
O) ~ 0.05-0.2 X(CO) ~ 1-3 10 -5 of H 2
Dusty04 - Paris, October 2004

Comparison with other CO lines (CSO
observations and ISO-LWS)
CO(6-5) and CO(4-3) also
compatible with C-shocks
of Vs ~ 10-15 km/s (ff~0.7
in CSO beam).
CO high-J (ISOLWS) trace
hotter component:
protostellar envelope or
faster/denser shocks in jet
bullets ?
data from Lis et al. 2002 (CSO) and Ceccarelli et
al. 1998 (LWS)
CSO (ff=0.7)
LWS (ff=1)
Need for Herschel water maps and nH diagnostics!
Dusty04 - Paris, October 2004

Shock Chemistry
C-precursor is
chemically active
H2 S(5)
(Flower & Pineau des
Forêts, Schilke et al., Bergin
et al.)
Mantle desorption
(eg. CH 3
OH)
Grain core sputtering
(SiO)
Endothermic
reactions (SO, CN…)
L1157 (Bachiller et al. 2001)
Dusty04 - Paris, October 2004
Cabrit et al. 1998

Shock chemistry: models
Complex variations (both
spatially and from source
to source) in abundances
of enhanced species
Evolutionary trends ?
Varying shock conditions ?
(nH,Vs,B)
Pre-processed medium ?
(Bachiller et al. 2001, Jorgensen etal.
2004)
Dusty04 - Paris, October 2004

Shock chemistry: models
C-shock nH = 10 4 cm-3 Vs = 30 km/s B = 100µ G
Complex variations (both
spatially and from source
to source) in abundances
of enhanced species
Evolutionary trends ?
CS
Varying shock SO conditions ?
(nH,Vs,B)
Pre-processed medium ?
CH3OH
H2CO
HCN
SiO
HCO+
Dusty04 - Paris, October 2004
N(CO)
(cm-2)

Shock chemistry and internal structure
Herschel: CH + , H 3
O + , NH, Tex(H 2
S,NH 3
…)
ALMA: Fully resolved magnetic precursor (size ~ 10 3
AU) in many tracers:
Chemical stratification vs. Models
Ion-neutral decoupling (HCO+)
J-front and H2 reformation zones vs. Optical/nearIR
Shock proper motions
Turbulent mixing-layers in non-planar shocks
Constraints on shock age and B-field
outflow dynamics, protostellar mass-loss & collimation
mechanism, evolutionary Dusty04 - scheme
Paris, October 2004

Photo Dissociation Regions
(PDRs)
Ideal laboratories for ISM physical and chemical processes
important targets for ALMA and Herschel
Herschel :
Cooling processes ([CII], [OI], CO, H 2
O) and thermal balance
Chemistry (H 2
O ; C- N- and O- hydrides including CH + )
Complex molecules (C clusters, PAHs, ...)
Dynamics of the hot interface
Dust properties (from SED)
ALMA : Small scale structures in the interface, turbulence, coupling of
gas dynamics and chemistry : time dependent effects
Line and continuum polarisation using radicals
Dusty04 - Paris, October 2004

C x
B x
B" x
A x
A" x
C" x
ODIN beams in IRAS 16293 outflow on CO map of Lis et al.(2002)