On the Production of Complex Molecules

1. On the Production of Complex Molecules in Regions of Star Formation Steven Charnley (NASA Goddard Space Flight Center) Yi-Jehng Kuan (ASIAA/NTNU) Yu-Sen Hsu (NTNU) Kuo-Song Wang (Leiden University) Great Barriers in High Mass Star Formation. Townsville, September 14 2010.

2. ISM-Solar System Connection?

3. Astrophysical Molecules PAHs HCOOC2H5 NH2CH2CN C3H7CN CH3OC2H5 Most complex molecules detected in hot molecular cores Chemical formation processes: gas or dust ? After A. Wootten

5. Origin of Complex Organics in Hot Cores/Corinos • Frozen remnants of cold cloud gas chemistry? • CO, C2H2, HCN … • Grain-surface chemistry (at ~10K or 30K)? • H2O, NH3, CH4, CH3OH, CO2 … • Hot chemistry in gas seeded with ice mantle constituents ? • methanol … (CH3)2O, HCOOCH3 ? • CH3OH2+ + CH3OH --> (CH3)2OH+ + H • ammonia … HCN, CH3CN, HC3N …

6. Molecule Formation on Dust Grains tacc ~ 1 particle/day About N~106 surface physisorption sites thop ~ 10-3 sec. tH ~ 10-12 sec. H, C, N and O atoms are most mobile H2 , H2O, NH3, CH4 formed by H addition reactions without activation energy barriers. Ehrenfreund, Charnley & Botta (2005)

7. Grain-surface Chemistry After Charnley & Rodgers (2006)

8. Stochastic Simulation of Gas-Grain Chemistry Constrained by ice observations: polar & apolar CO Rodgers & Charnley (2010) t al. 2004

10. Hot Chemistry in Mantle-Seeded Gas 100 K 300 K Rodgers & Charnley (2001)

11. Comparison with Observations • Search for predicted new molecules(e.g. Hollis et al. 2001; Fuchs et al. 2006; • Belloche et al. 2009) • Look for predicted differentiation(e.g. N-rich vs. O-rich gradients) • Map distributions and look for predicted chemical correlations • and anti-correlations (e.g. methanol parent-daughter relationships and • surface hydrogenation sequences). • Compare different formation theories.

12. Multi-molecular 1 mm Maps of Orion-KL Hsu et al. (2010)

13. SMA Maps of Orion-KL Hsu et al. (2010)

14. SMA Maps of Orion-KL Hsu et al. (2010)

15. Atomic Gradients Set the Prestellar Ice Composition? NH2CHO NI-rich C2H5OH CH3CHO CH2CO CI-rich HCOOH OI-rich Hsu et al. (2010)

16. SUMMARY • Prestellar ice composition could explain complex molecule distributions in hot cores. • - Competition for surface radicals (esp. HCO) by H, O,C, N atoms important • - surface hydrogenation is evident • - CH3OH, CH3OCH3 and HCOOCH3 strongly correlated …how are they connected? • - HCOOCH3: CH3OH2+ + HCOOH in gas is ruled out … HCO + CH3O on dust? • - large nitriles from N atom reactions on dust (Garrod et al. 2008;Belloche et al. 2009). • - origin of acetone? • Are there signatures of the predicted atomic gradients evident in IRDCs? • ALMA will: • - detect new (predicted?) organic molecules. • - produce maps of hot cores & corinos in many molecules. • - detect various isotopologues (13C, D, 15N, 18O) of complex • organics making possible `isotopic labelling’ measurements.

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18. Orion-KL: N-bearing Organics Wang et al. (2010)

19. Orion-KL: O-bearing Organics Wang et al. (2010)