Stefanie N. Milam NASA Goddard Space Flight Center Astrochemistry Laboratory

Transcription

1 Stefanie N. Milam NASA Goddard Space Flight Center Astrochemistry Laboratory

2 Reduce, Reuse, Recycle

3 What molecules to look for? Theoretical & Laboratory Studies Molecular Spectroscopy of prebiotic species. Spectral coverage, gas-phase, radicals/ions, $$$ What constitutes a detection? Full Spectrum Temperature Isotopologues Line Confusion. Interferometry

4 What molecules to look for? Theoretical & Laboratory Studies Molecular Spectroscopy of prebiotic species. Spectral coverage, gas-phase, radicals/ions, $$$ What constitutes a detection? Full Spectrum Temperature Isotopologues Line Confusion. Interferometry

5 H 2 CH + H 2 O C 3 NH 3 SiH 4 CH 3 OH CH 3 CHO CH 3 CO 2 H CH 3 CH 2 OH CH OH CN H 2 S HNC H 3 O + 3 (CC) 2 CN CH 4 NH 2 CHO CH 3 NH 2 HCO 2 CH 3 (CH 3 ) 2 O (CH 2 OH) 2 SO CO SO 2 HCN H 2 CO CHOOH CH 3 CN CH 3 CCH CH 3 C 2 CN CH 3 CH 2 CN CH 3 COCH 3 SO + CS NNH + CH 2 H 2 CS HCCCN CH 3 NC CH 2 CHCN C 7 H H(CC) 3 CN H(CC) 2 CH 3 SiO C 2 HNO NH 2 HNCO CH 2 NH CH 3 SH H(CC) 2 CN H 2 C 6 C 8 H SiS SiC CCS HOC + HNCS NH 2 CN C 5 H C 6 H CH 2 OHCHO 11 NO CP Most NH 2 NaCN molecules CCCN H 2 CCO HC 2 CHO c-ch comprised 2 OCH 2 NH 2 CH 2 CN H(CC) 4 CN NS CO + H + 3 MgNC HCO + 2 C 4 H CH 2 =CH 2 H 2 CC(OH)H HCl HF NNO AlNC CCCH c-c 3 H 2 H 2 C 12 of H, C, N, 4 O, S NaCl SiH HCO SiCN c-c 3 H CH 2 CN HC 3 NH + n-c 3 H 7 CN HO KCl + HCO PO + 13 SiNC CCCO C 5 C 5 N AlCl HD OCS H 2 D + C 3 S SiC 4 c-h 2 C 3 O H(CC) 5 CN >15 ions AlF CCH KCN HCCH H 2 C 3 PN AlO HCS + MgCN 6 rings HCNH + HCCNC >100 Carbon Molecules HCP Total >150 SiN c-sicc H 2 O + HCCN HNCCC 11 Silicon Species CCO 9 Metal Containing Molecules As of 05/2010 NH CCP H AlOH 2 CN H 2 COH + CH c-sic 3 HC(O)CN C 3 N - HSCN

6 Detection of many biologically relevant species in carbonaceous chondrites. Origin and Formation? in situ measurements are impossible for most astronomical objects. STARDUST Remote sensing. Connecting the simple chemistry of the ISM to the complex chemistry found in Meteorites, IDPs, and Comets. Pizzarello, S. (2004) OLEB, 34, 25

7 Detection of many biologically relevant species in carbonaceous chondrites. Origin and Formation? in situ measurements are impossible for most astronomical objects. STARDUST Remote sensing. Connecting the simple chemistry of the ISM to the complex chemistry found in Meteorites, IDPs, and Comets. Pizzarello, S. (2004) OLEB, 34, 25 Elsila et al. 2009

8 Detection of many biologically relevant species in carbonaceous chondrites. Origin and Formation? in situ measurements are impossible for most astronomical objects. STARDUST Remote sensing. Connecting the simple chemistry of the ISM to the complex chemistry found in Meteorites, IDPs, and Comets. Pizzarello, S. (2004) OLEB, 34, 25 Elsila et al. 2009

9 Start with simple chemistry Water was heated to induce evaporation Sparks were fired to simulate lightning At the end of one week they observed that as much as 10 15% was now in the form of organic compounds. Two percent formed amino acids Sugars, lipids, and some of the building blocks for nucleic acids were also formed. Reaction Chamber Methane, Ammonia, Water, and Hydrogen

10 Predictions of precursor species and/or new molecules based on known Interstellar composition and proposed reaction mechanisms. Gas-phase Dominated by ionneutral rx. Grain-surface E.g. H-atom addition (blue detected in SF). Snow et al. (2009)

11 Predictions of precursor species and/or new molecules based on known Interstellar composition and proposed reaction mechanisms. Gas-phase Dominated by ionneutral rx. Grain-surface E.g. H-atom addition (blue detected in SF). Herbst and van Dishoeck 2009, adapted from Charnley (2001; 1997)

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13 Species RAFGL NGC 7538 W33A c Elias 16 c Comets c 7009S a IRS9 b H 2 O CO CO CH 3 OH < CH NH 3 13 d OCN <0.5 (a) d Hendecourt et al (c) Gibb et al (b) Whittet et al (d) Lacy et al. 1998

14 Bernstein, Sandford, Allamandola, Sci. Am. 7,1999, p26

15 Photochemistry 188 min UV exposure 2342 cm -1 CO cm -1 -CN 2167 cm -1 OCN cm -1 CO 2090 cm -1 -NC Before Wavelength (cm-1) Other bands such as aromatic ketone groups (~1685 cm -1 ) are blended with water features. Pyrimidine:H2O ~ 1:20 (Nuevo et al. 2009)

16 Multiple Groups working on simulating interstellar ice (photo)chemistry. Able to produce complex organics of astrophysical interest e.g. ethylene glycol (Hudson et al. 2005). Amino Acids and lipid-like species synthesized in ices (Dworkin et al. 2001, Bernstein et al. 2002, Munoz Caro et al. 2002). Nucleobases? Other prebiotic species?

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18 (Milam, Nuevo, et al., in preparation) Uracil also confirmed in Pyrimidine and H 2 O ices (Nuevo et al. 2009).

19 Half-lives a Mixture UV (cm 2 mol -1 ) Laboratory (min) DISM (yr) DC (Myr) Solar System (hr) Pyrimidine:NH 3 (1:25) ,400 1, Pyrimidine:H 2 O (1:20) b , Pyrimidine:NH 3 :H 2 O (1:2:20) ,300 1, Pyrimidine:Ar (1:750) c a Estimated according to the UV photon fluxes for Laboratory: 2x10 15 photons cm -2 s -1 (Elsila et al. 2007); DISM: 8x10 7 photons cm -2 s -1 (Mathis et al. 1983); DC: 1x10 3 photons cm -2 s -1 (Prasad & Tarafdar 1983); and Solar System: 3x10 13 photons cm -2 s -1 (Peeters et al. 2005). b Data from Nuevo et al. (2009). c Data from Peeters et al. (2005). Glycine: Solar System ~ 0.5 hr (Peeters et al. 2003) Milam et al., in preparation

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21 Amino Acids 1. Brown et al. (1979) Parkes, Onsala, NRAO 11m 2. Hollis et al. (1980) NRAO 11m 3. Snyder et al. (1983) Haystack, NRAO 140, NRAO 11m 4. Berulis et al. (1985) Pushchino 5. Guelin and Cernicharo (1989) IRAM 30m 6. Combes et al. (1996) IRAM 30m 7. Ceccarelli et al. (2000) IRAM 30m 8. Kuan et al. (2003) NRAO 12m 9. Hollis et al. (2003) VLA 10. Crovisier et al. (2004) IRAM 30m, PdB 11. Snyder et al. (2005) NRAO 12m, SEST 12. Cunningham et al. (2007) Mopra, ATCA 13. Jones et al. (2007) ATCA 14. Guelin et al. (2008) IRAM 30m, PdB, GBT Nucleic Acids Brunken et al. (2006) ARO 12m, IRAM 30m Kuan et al. (2003) JCMT Sugars Hollis et al. (2000) NRAO 12m Halfen et al. (2006) NRAO 12m Widicus Weaver & Blake (2005) CSO Apponi et al. (2006) ARO 12m, GBT

22 Cooper et al. 2001, Nature

23 What molecules to look for? Theoretical & Laboratory Studies Molecular Spectroscopy of prebiotic species. Spectral coverage, gas-phase, radicals/ions, $$$ What constitutes a detection? Full Spectrum Temperature Isotopologues Line Confusion. Interferometry

24 Larger Molecules more complex spectrum, larger rotational partition function Frequency Coverage Most experiments are designed to operate at restricted frequencies. (physical design) Extrapolation of frequencies can often yield errors (Snyder et al. 2005). Direct measure or high precision Hamiltonian (known 1:10 7 ) Experimental challenges Solids, radicals, ions, etc. Resources $$$ Astrophysics Databases Splatalogue has ~1000 species

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28 What molecules to look for? Theoretical & Laboratory Studies Molecular Spectroscopy of prebiotic species. Spectral coverage, gas-phase, radicals/ions, $$$ What constitutes a detection? Full Spectrum Temperature Isotopologues Line Confusion. Interferometry

29 Observe every favorable transition. E.g. Halfen et al glycolaldehyde Line Confusion Interstellar Weeds (HCOOCH3) Beam Dilution Fine and Hyperfine Structure Temperature(?) Distribution E.g. Belloche et al amino acetonitrile Isotopologues

30 (K) T A * Observe every favorable transition. E.g. Halfen J=5/2-3/2 et al glycolaldehyde Line Confusion Interstellar Weeds (HCOOCH3) Beam Dilution Fine and Hyperfine Structure Temperature(?) Distribution F=5/2-5/2, F=3/2-3/2 F=3/2-1/2, F=7/2-5/2, F=5/2-3/2 E.g. Belloche et al amino acetonitrile Isotopologues Milam et al F=3/2-1/2 F=1/2-1/2 F=5/2-3/ F=3/2-3/2 F=1/2-3/2 J=3/2-1/ Frequency (GHz) Y CVn 12 CN:N=2-1 J=3/2-3/ F=5/2-5/2 F=5/2-3/2 F=3/2-5/2 F=3/2-3/2 F=3/2-1/2, F=1/2-3/2 F=1/2-1/2

31 Observe every favorable transition. E.g. Halfen et al glycolaldehyde Line Confusion Interstellar Weeds (HCOOCH3) Beam Dilution Fine and Hyperfine Structure Temperature(?) Distribution E.g. Belloche et al amino acetonitrile Isotopologues

32 What molecules to look for? Theoretical & Laboratory Studies Molecular Spectroscopy of prebiotic species. Spectral coverage, gas-phase, radicals/ions, $$$ What constitutes a detection? Full Spectrum Temperature Isotopologues Line Confusion. Interferometry

33 (K) T R * Lines per 100 MHz at 3mm (10 mk peak to peak)! 0.4 U C 2 H 3 CN U C 2 H 3 CN C 2 H 5 CN HCOOCH 3 U C 2 H 3 CN CH 3 CHO CH 3 CHO + C 2 H 5 CN CH 3 CHO + C 2 H 3 CN C 2 H 3 CN + C 2 H 5 CN 0.2 OCS 13 CS U HCOOCH 3 C 2 H 5 OH CH 3 CHO HCOOCH 3 U HCOOH C 2 H 5 OH + (CH 2 OH) 2 U HCOOCH 3 CH 3 CHO U (CH 3 ) 2 O C 2 H 3 CN SgrB2(N): 2 hr. integration - 3 sigma noise: 9 mk - SSB: no image lines HCOOCH 3 37 Indentified Features 35 Unidentified Features ~6 lines per 100 km/s T RMS = K (theoretical) C 2 H 5 OH CH 3 CHO C 2 H 5 CN C 2 H 3 CN C 2 H 5 OH U NH 2 CH O CH 3 NH 2 C 2 H 5 CN HNCO (CH 3 ) 2 O HCOOCH 3 + C 2 H 3 CN C 2 H 3 CN C 2 H 5 CN U Halfen and Ziurys Frequency (MHz) From L. Ziurys

34 Kinematically resolve individual cores Extended envelope: n(h 2 )<10 4 cm -3 R=20 pc (~90) HII regions, masers, hot cores: n(h 2 )=10 7 cm -3 T k = K D=14 Hot ring: T k = K Moderate density cloud: n(h 2 )=10 5 cm -3 T k =40-80 K Structures and components of Sgr B2 region (adapted from Goicoechea et al. 2004).

35 Kinematically resolve individual cores Extended envelope: n(h 2 )<10 4 cm -3 R=20 pc (~90) HII regions, masers, hot cores: n(h 2 )=10 7 cm -3 T k = K D=14 Hot ring: T k = K Moderate density cloud: n(h 2 )=10 5 cm -3 T k =40-80 K Structures and components of Sgr B2 region (adapted from Goicoechea et al. 2004). 6 cm: Benson & Johnston, 1984, ApJ

36 Low mass protostar L483-mm Comparison between the single-dish spectra (grey) and spectra extracted from the interferometer datacubes convolved with the single-dish beam (black). Each spectrum from the interferometer data has furthermore been multiplied by a factor 5 to make comparison between the lineshapes easier. (Jorgensen 2004)

37 Friedel et al. (2004) ApJ, 600, 234

38 ALMA Angular resolution Down to 10 milliarcsecond scales Bandwidth Over 800 GHz 8 RX bands Spectral resolution Line profiles, small linewidths (SF, comets) Limitations Loss of extended flux combination with Single Dish studies and multiwavelength approach. Laboratory Spectroscopy Limited (U-line Era?) Imaging of ALL gas-rich regions from ISM SF Disks solar system bodies - CSEs

39 Interstellar Connection? Disk/Comet connection? Molecular Inventory: Organics, Isotopes, Gas- Grain Chemistry? Mumma et al. (2003)

40 Preserved material from presolar nebula Pristine from molecular cloud Processing in presolar nebula Cometary chemistry Molecular Inventory now ~ 25 species ++ Short lived ALMA sensitivity and BW Spatial Distribution Extended Sources? Bockelee-Morvan et al. 2000

41 Preserved material from presolar nebula Pristine from molecular cloud Processing in presolar nebula Cometary chemistry Molecular Inventory now ~ 25 species ++ Short lived ALMA sensitivity and BW Spatial Distribution Extended Sources? H2CO: Milam et al. 2006

42 About 5/yr since ~1970. Telescope Effect vs. Spectroscopy? NRAO H2CO NRAO 12m (1967) 1970 CO IRAM 30m (1984) BIMA (1986) JCMT and CSO (1987 and 1988) PdB (1990 s) ISO (1995) Herschel (2010) 9 new molecules in new extragalactic in 2010 Thaddeus P Phil. Trans. R. Soc. B 2006;361:

43 ALMA will help resolve most of the current issues associated with current studies of prebiotic molecules in space. Full spectrum, combination with Single Dish, mutiwavelength, high resolution (spectral and angular) are all necessary for the detection of complex species in most objects. Theoretical and Laboratory Studies can guide searches for biomolecules, and/or their precursors. High resolution laboratory spectroscopy will be a key limitation to the detection of new species.

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