Testing grain-surface chemistry in massive hot-core regions and the laboratory (A&A, 465, 913 and A&A submitted) Suzanne Bisschop Jes Jørgensen, Ewine van Dishoeck, Evelyn de Wachter, Guido Fuchs, Harold Linnartz

Origin of complex molecules in star- forming 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 :detected in gas phase ––:detected in solid state

Observed JCMT spectra and correlations Observed abundance relations and excitation temperatures used to classify molecules N(X)/bf CH 3 OH H 2 CO CH 3 OCHO CH 3 OCH 3 C 2 H 5 OH HNCONH 2 CHO Expected to form from CH 3 CHO, but precursor detected only in cold gas Bisschop et al., A&A, 465, 913 Some model relations confirmed, some not Empirical correlations

Testing the CH 3 CHO + H  C 2 H 5 OH reaction in the laboratory CH 3 CHO ices are bombarded at mbar with H-atoms (flux: ~8x10 13 atoms s -1 ) Yields of ~20% C 2 H 5 OH are detected with a QMS mass spectrometer! But CH 4, H 2 CO and CH 3 OH are formed as well => fragmentation Bisschop et al., submitted to A&A

Conclusions ● Experiments show that formation of C 2 H 5 OH from CH 3 CHO in the ice is possible ● Remaining question: why is no CH 3 CHO 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 + laboratory experiments of interstellar ice analogues  toward understanding chemical processes in star forming regions Based on Tielens and Charnley :detected in gas phase ––:detected in solid state Confirmed!

Extra slides

Rotational temperatures Hot Cold. H 2 CO CH 3 OH CH 3 CN C 2 H 5 CN CH 3 OCH 3 NH 2 CHO CH 3 CCH.

SURFRESIDE set-up H2H2 To rotary stage gas To rotary stage Turbo Pump Main QMS Atomic Source 7:1 / 45:8 ellipsoidal mirror InSb / MCT l.N 2 cooled IR detector External link to FTIR Spectrometer From FTIR Spectrometer  :18 off-axis parabolic mirror Turbo Pump To rotary stage

Structure protostellar envelope Cold outer envelope: D~10 17 cm T~40-60 K n(H 2 )~10 6 cm -3 Warm envelope: D~ cm T~ K n(H 2 )~ cm -3 Hot core: D~10 16 cm T~ K n(H 2 )~ cm -3 Based on Figure for G by Gibb et al. 2001, ApJ, 545, 309 ices gas

Grain-surface processes AB diffusion A A AB B B A2A2 Eley-Rideal Mechanism A2BA2B A2BA2B A2BA2B A2A2 Langmuir - Hinshelwood Mechanism Fraser et. al. A&G, 43, no. 2, 2.10 (2002)

H2OH2O NH 4 + CH 4 CO 2 Silicate Boogert, Pontoppidan, Oberg, Bottinelli et al 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 Fraser et al. 2007, Bouwman et al Large overall similarity with high-mass YSOs - - NH 3, CH 3 OH detected in some sources with high abundances (10% of water) - - New lab data on HCOOH, CO 2 -CO, H 2 O-CO 2, H 2 O-CO, NH 3 -H 2 O to interpret Spitzer spectra