1. Some Chemistry in Assorted Star-forming Regions Eric Herbst

2. Some Regions Associated with Star- Formation pre-stellar cores (L1544) low mass protostars (IRAS 16293)  protoplanetary disks  Hot cores  PDR’s

3. A pre-stellar core (cold but with a dense center)

4. H 2 D + - detected by Caselli et al. (2003) D/H = 1.5 x 10 -5 “H 2 D + is the main molecular ion in the central..”

5. L1544 – a prestellar core CCS – gray scale Dust emission peak

6. The model: multiply deuterated species are now observed in the ISM observations support the link between high fractionation and CO depletion we present a pseudo-time-dependent model of deuterium chemistry, including all analogues of H 3 +, NH 3, CH 3 OH HD 2 + and D 3 + may be important even in modeling singly deuterated species

7. Fractionation in the gas-phase…. H3+H3+ CO, N 2, O HCO+ N 2 H+ OH+ H2D+H2D+ e- HD DCO+, HCO+ N 2 D+, N 2 H+ OD+, OH+ CO, N 2, O e- H2H2 H H H H 2 H H H D HD H H 2 D

8. When species are depleted…. H3+H3+ CO, N 2, O HCO+ N 2 H+ OH+ H2D+H2D+ e- HD DCO+, HCO+ N 2 D+, N 2 H+ OD+, OH+ CO, N 2, O e- H2H2 H H H H 2 H H H D HD H H 2 D

9. At higher densities…. H3+H3+ CO, N 2, O HCO+ N 2 H+ OH+ H2D+H2D+ e- HD DCO+, HCO+ N 2 D+, N 2 H+ OD+, OH+ CO, N 2, O e- H2H2 H H H H 2 H H H D HD H H 2 D

10. Accretion model without HD 2 + and D 3 + : n(H 2 )10 4 (cm -3 )10 6 (cm -3 ) H 2 D + /H 3 + 0.93827.37 DCO + /HCO + 0.2170.492 N 2 D + /N 2 H + 0.2150.484 D/H0.0750.355 NH 2 D/NH 3 0.3131.208 HDCO/H 2 CO0.1330.381 Times of peak D/H ratios: 10(6) yr and 2 x 10(4) yr

11. Deuterium fractionation: H 3 + + HDH 2 D + + H 2 H 2 D + + COHCO + + HD 2 / 3 DCO + + H 2 1 / 3 Maximum DCO + /HCO + ratio is 0.5

12. Deuterium fractionation: H 2 D + + HDHD 2 + + H 2 HD 2 + + COHCO + + D 2 1 / 3 DCO + + HD 2 / 3 DCO + /HCO + ratio reflects the total degree of deuteration of H 3 + HD 2 + + HDD 3 + + H 2 D 3 + + CODCO + + D 2 1

13. Fractional abundances:

14. Molecular D/H ratios:

15. A comparison of the homogeneous model with observations of CO and D 2 CO: observations model (Observations from Bacmann et al. 2002; 2003) Heterogeneous shell model does much better!

16. Fractionation on Grains One of the strongest predictions of the pre- stellar core model is that the abundance ratio of D to H atoms in the gas becomes quite high (0.1 – 1.0). In reality, these atoms strike dust particles and react to form both normal and deuterated species!! These species stay on the grains until star formation begins to occur and temperatures rise!

17. Accretion and Diffusion DUST H D CO Surface reactions produce the following molecules : H 2 CO, HDCO, D 2 CO CH 3 OH, CH 3 OD CH 2 DOH, CHD 2 OH CH 2 DOD, CHD 2 OD CD 3 OH, CD 3 OD O H 2 O, HDO, D 2 O, CO 2, H 2, HD, D 2

18. The Protostar IRAS 16293-2422 Temperatures have warmed up to near 100 K close to the budding star and 50 K somewhat farther removed. The following methanol isotopomers have been detected: CH3OH, CH3OD, CH2DOH, CHD2OH, CD3OH in addition to HDCO and D2CO. The belief is that these species have very recently come off grains.

19. Dust continuum – IRAS 16293

20. Methanol fractionation from a grain surface chemistry model: AbundanceCH 3 OH1 x 10 -7 FractionationCH 3 OD0.22 CH 2 DOH0.8 CH 2 DOD0.16 CHD 2 OH0.2 CHD 2 OD0.048 CD 3 OH0.02 CD 3 OD0.004 Accreting D/H ratio = 0.4 (Stantcheva & Herbst 2003) IRAS 0.04 0.9 0.2 0.03

21. Methanol fractionation from a protostellar model. T=50 K; n(H 2 )=10 6 cm -3 What happens as the evaporated material ages?

22. After methanol desorbs from the grains: CH 3 OD CH 2 DOH CH 3 ODH + CH 2 DOHH + CH 3 OD CH 3 OH CH 2 DOH H3+H3+ e-e- e-e- H3+H3+ e-e- Osamura et al. 2004

23. Compared with the observations: Observations of IRAS 16293-2422 from Parise et al. 2002; 2003

24. HOT MOLECULAR CORES Hot cores are regions of warm, quiescent gas near high-mass star-forming regions. Temperatures are 100-300 K and densities are typically 10 7 K. They are associated with a variety of saturated gas-phase organic molecules: methanol, ethanol, acetaldehyde, methyl formate, acetic acid, glycolaldehyde, ethylene oxide, dimethyl ether, and possibly diethyl ether, glycine, and ethylmethyl ether.

25. OMC: KL HOT CORES

26. HOT MOLECULAR CORES II As in protostellar sources, the chemistry is associated with evaporation from the dust, although the post-evaporation gas-phase chemistry may be crucial in producing larger species from the precursor methanol. Key reactions in chain to form methyl formate:

27. Ab Initio Calculations

28. TWO EXPERIMENTS 1) SIFT AT HANSCOM AF BASE dominant product cluster ion (high density) 2) ICR AT WATERLOO, CANADA dominant product CH 3 OCH 2 + (low density) CONCLUSION: no major channel to produce protonated methyl formate We don’t know how it is made in hot cores. There is work left for you to do!!!!!