Emmanuel Dartois, IAS, Orsay, France Ivan Alata, Markus ...lana/DUST2016/... · Hydrogenated amorphous carbons (a-C:H or HAC) Godard et al. 2013, Sandford et al. 1991 e.g. Sandford

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


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(


OLEF./AROM.*BACKBONE*

***Arom.*CH*UPPER*LIMIT*

OLEF.*

Dartois,(Geballe,(Pino(et(al.(2007(

IRAS*08572+3915*

OBSERVED*

Precursor

Substrate

ISM (ext. galaxies)


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


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


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


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(


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.


Photolytic H2 formation rate

VUV Rate coefficient

Yield(Destruction cross-section( VUV photons flux(

extinction(CH abundance(


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


Alata(et(al.(2015;(Jallat(2015(

C3Dy C4Dy C2Dy CD4

Other photolytic products:

a-C:D


C3Hy C4Hy C2Hy


CH4

a-C:H


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:(


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*


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(



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


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


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(


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*


IR monitoring cross section of the solid phase processing

Xe21+ @ 0.6 GeV


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


Experiments @ GSI (Darmstadt)

Post Irradiation TPD 5K/min

Ion*Beam**

QMS*

40K 100K

300K


Dartois(et(al.(2016(submived(to(A&A(


Xe21+ @ 0.6 GeV


Dartois(et(a

l.(2016(sub

mived

(to(A&A(


f (Z)

Φ(Z,E)

MeV/nucleon

Atomic number Z

Φ(Z

,E)

Rel

ativ

e ab

unda

nce


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]=(


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).


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(


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(


Documents

Emmanuel Dartois, IAS, Orsay, France Ivan Alata, Markus ...lana/DUST2016/... · Hydrogenated amorphous carbons (a-C:H or HAC) Godard et al. 2013, Sandford et al. 1991 e.g. Sandford