Emmanuel Dartois, IAS, Orsay, France Ivan Alata, Markus Bender, Karine Beroff, Marin Chabot, Gustavo A. Cruz-
Diaz, Marie Godard, Aurélie Jallat, Rafael Martín-Doménech, Guillermo M. Muñoz Caro, Thomas Pino, Daniel Severin, Christina Trautmann
DUST2016, Garching, 13-16 Sept 2016
Outline(
Lupus 3 dark cloud © ESO/F. Comeron(
Context
VUV
Hydrocarbons production from a-CH dust
Application to DISM
Modeling of a PDR
CRs
SHI of ISM carbonaceous dust grain analogues
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
(Nano1)(Diamond(
Hydrogenated((amorphous(carbon(Amorphous((
carbon(
Ice(mantles((residues(
AIBs1PAHs(:((Class(A(to(C(Fullerenes(
Some carbonaceous solids observed in the ISM
+ organic matter
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Hydrogenated amorphous carbons (a-C:H or HAC)
CH stretch abs. observed against IR bkgd sources
Pendleton et al. 1994
Viehmann et al. A&A 2004
Pendleton(&(Allamandola(ApJ(2002(
UGC1
2158((Credit(N
ASA
/ESA
(
Dartois,(Geballe,(Pino(et(al.(2007(
DISM
Sun(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
OLEF./AROM.*BACKBONE*
***Arom.*CH*UPPER*LIMIT*
OLEF.*
Dartois,(Geballe,(Pino(et(al.(2007(
IRAS*08572+3915*
OBSERVED*
Precursor
Substrate
ISM (ext. galaxies)
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Hydrogenated amorphous carbons (a-C:H or HAC)
Godard et al. 2013, Sandford et al. 1991
e.g. Sandford et al. 1995, Pendleton et al. ApJ 1994; Duley et al. ApJ 1994, 1998; Dartois et al 1997
τ (3.4)(:(2.6%(to(35%((lab(HAC)(of(cosmic(C((
Dartois & Munoz Caro 2007
• τ(6.85)(~(0.12(τ(Silicates)(• 15%(+17%(of(the((cosmic(
carbon(• Up(to(40%(in(extreme(cases(?(
CH stretch abs. Galactic ISM CH bendings abs. extragalactic DISM
e.g. Risaliti et al. 2006, Imanishi et al. 2006; Mason et al. 2004, 1998; Pendelton et al 1994
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
PDR: Photon Dominated Regions
One-dimensional Photo-Dissociation Region, The Horsehead (PDR)
C2, C3, C2H2, CCH, c-C3H2, C4H ….
Hydrocarbons molecules detections
Dense, cold molecular gas
Guzman(et(al.(2015(
C3H+
C2H
Top-down chemistry ?
Pety(et(al.(2005(
VUV
C3H2
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Lyman-alpha 121.6 nm MgF2(
Cutoff(115nm(
Madrid(2013(G.(Adolfo,(G.(M.(Munoz(Caro(
Gredel(et(al.(1989(Chen(et(al.(2014;(Cruz1Diaz(et(al.(2014(
LABORATORY* ASTRO*MODEL*
Study the evolution of a-C:H under simulated ISM conditions Interaction with VUV photons & Cosmic rays
Objectives
< Ephoton > = 8.6 eV/photon Ф= 2.7 x 1014 photon.cm-2.s-1
Test astrophysical models with the photoproducts H2 formation Formation of hydrocarbons in PDRs regions. Astrophysical timescales
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Experiments
P ~ 2x10-8 mbar
45°*
Vacuum*chamber*
IR*Beam**
QMS*Quadrupole*Mass**Spectrometer*
VUV*source*
Bunch*of*ions*
IR*detector*Beam*spliUer*
H2*
RF*cavity*
T~10K*
VUV*
Diaphragm**
PH2=*0.75*mbar*
a-C:H
Irradiation at T=10 K
TPD 5K/min
I. Alata
P ~ 10-10 mbar DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
To enhance detection limits, both a-C:H and a-C:D analogues
a-C:D a-C:H
a-C:H
a-C:D
Opt
ical
dep
th
Wavenumber
Num
ber o
f N(C
-H) &
N(C
-D)
a-C:D
destruction cross-section σCH(VUV) = 3 ± 0.9 × 10−19 cm2
σCH(VUV) = 1(to(5(×(10−19(cm2(
Mennella(et(al.(1999,(2001(Alata(et(al.(2014(
σCH(VUV) similar(
Gadallah(et(al.(2011,2013(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
D2
5h irradiation then TPD 5K/min
Post irradiation TPD
Mean VUV penetration depth (120-160nm) measured ~ 80 nm (SOLEIL Synchrotron – DISCO Beam line).
UV-VUV
Formation on the surface & in the volume
Blank exp.
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Photolytic H2 formation rate
VUV Rate coefficient
Yield(Destruction cross-section( VUV photons flux(
extinction(CH abundance(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Habart(et(al.(2004(
VUV H2 Rate coefficient
With 5-10% C locked into a-C:H &
Rc up to 1.25-2.5 10-16 cm3s-1
This(mechanism(can(provide(high(H2(formadon(rates(at(low(to(high(grain(T(
PDR: χ/n(H) up to 0.25
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Alata(et(al.(2015;(Jallat(2015(
C3Dy C4Dy C2Dy CD4
Other photolytic products:
a-C:D
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
C3Hy C4Hy C2Hy
Alata(et(al.(2015;(Jallat(2015(
CH4
a-C:H
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Alata(et(a
l.(2015;(Jallat(2
015(
Photoproduced ( ( (Yield( ( ( ((((Photolydc(rate(species ( ( ( ( ((%) ( ( ( ( ((10−14s−1)((______________________________________________________________(H2( ( ( ( ( ( (96.5(((±3.0)( ( ( (2.79(×(103((
CH4(( ( ( ( ( (3.0((((±1.0)( ( ( (86(
C2H2( ( ( ( ( (0.081((((±0.060) ( (2.3((C2H4( ( ( ( ( (0.195((((±0.072) ( (5.6((C2H6( ( ( ( ( (0.246((((±0.063) ( (7.1((
C3H4( ( ( ( ( (0.042((((±0.036) ( (1.2((C3H6( ( ( ( ( (0.114((((±0.057) ( (3.3((C3H8( ( ( ( ( (0.075((((±0.060) ( (2.2((
C4H4( ( ( ( (≤ (0.009( ( ( ( (1(C4H6( ( ( ( (≤ (0.027( ( ( ( (1((C4H8( ( ( ( (≤ (0.027( ( ( ( (1(C4H8( ( ( ( (≤ (0.027( ( ( ( (1(
a1C:H(+(VUV(photon(!(a1C:H(+(CxHy((
Model(I(} Model(II(} Model(III(}
Model(implementadon:(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Le(Pedt(et(al.(2006(1st step Meudon Code:
Radiative transfer + Chemical reactions + Thermal balance
Horsehead(nebula(T(≈(100(K((nH(≈(2.105(cm3((χ(≈(60(Draine(units((ζ(=(5.10117(s11([S]/nH(=(3.5x1016((
A. Jallat
NH (c
m-3
)*
Distance to the star*
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
C4H*A
bund
ance
/ N
H*
Abu
ndan
ce ra
tio*
Initial*
+a-C:H photolysis*
Distance to the star*
2nd step Nahoon Code: Time dependence of a-CH perturbation
Wakelam(2006(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Alata(et(al.(2015;(Jallat(2015(
CCH( c-C3H(
C4H(
c-C3H2(
Abu
ndan
ce(
Abu
ndan
ce
ratio
(
PDR advection front velocity: ~ 1 km/s
d(0.5AV) ~ 7.8 × 1015 cm, equivalent to 2.5−5 × 103 yrs
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Bulk of the interstellar grains as important as surface
a-C:H (& polyaromatic dust of AIBs-PAHs) photolytic reactions ! formation of H2 & hydrocarbons in the ISM
Reduce gap between observed and modeled hydrocarbons abundances in PDRs
Destruction timescale ! in line with PDR advection front velocity (1 km/s)
Models chemical network ! include highly hydrogenated hydrocarbon species.
Take home message VUV
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
One-dimensional Photo-Dissociation Region, The Horsehead (PDR)
Dense, cold molecular gas
Guzman(et(al.(2015(
C3H+
C2H
Top-down chemistry ?
Pety(et(al.(2005(
C3H2
CRs(in(Diffuse(ISM(&(clouds:(( ((( ( (SHI(of(ISM(carbonaceous(dust((grain(analogues(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Experiments @ GSI (Darmstadt)
Irradiation at T=25-300 K
+ TPD 5K/min a-C:H sample
Ion Beam FTIR
Mass spectrometer
45°*
Vacuum*chamber*
Ion*Beam**
QMS*Quadrupole*Mass**Spectrometer*
IR*detector*
VUV*
a-C:H sample
Ion*Beam**
a[C:H*
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
IR monitoring cross section of the solid phase processing
Xe21+ @ 0.6 GeV
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
C3Hy C4Hy C2Hy
Dartois(et(a
l.(subm
ived
(to(A&A(
CH4
a-C:H
Ion*Beam**
Cosmic rays release carbonaceous species
H2
Feeds the ladder of large gaseous C species
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Experiments @ GSI (Darmstadt)
Post Irradiation TPD 5K/min
Ion*Beam**
QMS*
40K 100K
300K
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Dartois(et(al.(2016(submived(to(A&A(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Xe21+ @ 0.6 GeV
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Dartois(et(a
l.(2016(sub
mived
(to(A&A(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
f (Z)
Φ(Z,E)
MeV/nucleon
Atomic number Z
Φ(Z
,E)
Rel
ativ
e ab
unda
nce
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
Se(Z,E) f (Z)
η(Se) Φ(Z,E) +
∑(∫(σ(Z,E) f(Z)(Φ(Z,E) dE(CR
σ(Z,E)(=(σ(Se(Z,E))(
RdGCR([s11]=(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
RdGCR [s-1] ≈ 8x10-16 s-1 (for ζ = 3.5x10-16 s-1)
nX 10−11 η(X)
Diffuse medium (τd << 1) CR insufficient to be significant
ntot e−τd f[N(X)] ≈ a few
high energy CR penetrates deep in dense regions
Photodissociation e−τd ! secondary UV induced (10−3/10-4 at AV > 7)
abundance increases to values closer to observations and models (Guzmán et al. 2015; Alata et al. 2015; Pety et al. 2012).
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
One(more(slide…(" SHI in CR, desp. low abundance, have a role to play
" CRs less significant for a-C:H in DISM
" CRs induce a top-down chemistry for refractory dust grains in dense clouds
" CRs radiolysis participate to the erosion of icy grains see poster by C. Jäger
" CRs participate to the replenishing of the dense cloud gas phase by ice e- sputtering
" Lab eval needed, many space processes are concomitant (CRs, surface, thermal, UV, shocks …)
Fantasdc(4(
Sabri(et(al.(2015(
e.g(Dartois(et(al.(2013;(Rothard(et(al.(2016(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(
I.(Alata(L.(Gavilan(E.(Dartois((
T.(Pino(K.(Beroff((
A.(Jallat(((M.(Chabot( G.(M.(Muñoz(Caro(
G.(A.(Cruz(Diaz(R.(Mar|n1Doménech(
Thank you ! M.(Bender(D.(Severin(C.(Trautmann((
M.(Godard(
DUST20161(E.(Dartois(–(Garching1(15(Sept(2016(