Testing grain-surface chemistry in massive Testing grain-surface chemistry in massive hot-core regions and the laboratoryhot-core regions and the laboratory

(A&A, 465, 913 and A&A submitted)(A&A, 465, 913 and A&A submitted)

Suzanne BisschopSuzanne Bisschop

Jes JJes Jørgensen, Ewine van Dishoeck, Evelyn de ørgensen, Ewine van Dishoeck, Evelyn de Wachter, Guido Fuchs, Harold LinnartzWachter, Guido Fuchs, Harold Linnartz

17-08-0717-08-07

Origin of complex molecules in star-Origin of complex molecules in star-forming regionsforming regions

Wealth of complex organic molecules detected in protostellar hot core regions (both high- and low- mass!)

Origin unclear:

Grain-surface chemistry

High temperature gas phase chemistry

Aim: test grain surface chemistry proposed by Tielens & Charnley through combined observations and lab experiments

Based on Tielens and Charnley 1997

---:detected in gas phase––:detected in solid state

Observed JCMT spectra and correlationsObserved JCMT spectra and correlations

Observed abundance relations and excitation temperatures used to classify molecules

N(X)/bf

CH3OH H2CO

CH3OCHO

CH3OCH3C2H5OH

HNCO NH2CHO

Expected to form from CH3CHO, but precursor detected only in cold gas

Bisschop et al., A&A, 465, 913

Some model relations confirmed, some not

Empirical correlations

Testing the CH3CHO + H C2H5OH reaction in the laboratory

CH3CHO ices are bombarded at 10-10 mbar with H-atoms (flux: ~8x1013 atoms s-1)

Yields of ~20% CYields of ~20% C22HH55OH are detected with a QMS mass spectrometer!OH are detected with a QMS mass spectrometer!But CHBut CH44, H, H22CO and CHCO and CH33OH are formed as well => fragmentationOH are formed as well => fragmentation

Bisschop et al., submitted to A&A

ConclusionsConclusions● Experiments show that formation

of C2H5OH from CH3CHO in the ice is possible

● Remaining question: why is no CH3CHO observed in hot cores?

– It is fully hydrogenated in the ice before desorption

– It is destroyed in the ice by thermal/energetic processing

Molecular line observations + Molecular line observations + laboratory experiments of laboratory experiments of interstellar ice analogues interstellar ice analogues toward toward understanding chemical processes understanding chemical processes in star forming regionsin star forming regions

Based on Tielens and Charnley 1997

---:detected in gas phase––:detected in solid state

Confirmed!

Confirmed!

Extra slides

Rotational temperaturesRotational temperatures

Hot

Cold

.

H2CO

CH3OH

CH3CN

C2H5CNCH3OCH3

NH2CHO

CH3CCH

.

SURFRESIDE set-upSURFRESIDE set-up

H2

To rotarystage

gas

To rotarystage

TurboPump

Main QMS

AtomicSource

7:1 / 45:8 ellipsoidalmirror

InSb / MCTl.N2 cooledIR detector

External linkto FTIR

Spectrometer

From FTIRSpectrometer

:18 off-axisparabolic mirror

TurboPump

To rotarystage

Structure protostellar envelope

Cold outer envelope:D~1017 cmT~40-60 Kn(H2)~106 cm-3

Warm envelope:D~1016-1017 cmT~100-150 Kn(H2)~106-107 cm-3

Hot core:D~1016 cmT~150-200 Kn(H2)~107-108 cm-3

Based on Figure for G327.3 1 by Gibb et al. 2001, ApJ, 545, 309

ices

gas

Grain-surface processesGrain-surface processes

AB

diffusion

A

A

AB

B

B

A2

Eley-RidealMechanism

A2B

A2BA2B

A2

Langmuir - Hinshelwood Mechanism

Fraser et. al. A&G, 43, no. 2, 2.10 (2002)

H2O

NH4+

CH4CO2

Silicate

Boogert, Pontoppidan, Oberg, Bottinelli et al. 2007

Ices toward low-mass protostars with Spitzer

Spitzer observations of ices toward low-mass YSOs

Boogert et al. 2004, Oberg et al. 2007, Bisschop et al. 2007Fraser et al. 2007, Bouwman et al. 2007

-- Large overall similarity with high-mass YSOs-- NH3, CH3OH detected in some sources with high abundances (10% of water)-- New lab data on HCOOH, CO2-CO, H2O-CO2, H2O-CO, NH3-H2O to interpret Spitzer spectra