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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