1. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH1 THE GBT PRIMOS PROJECT REPORT FROM THE FIRST YEAR OF OBSERVATIONS. Anthony J. Remijan NRAO Assistant Scientist – ALMA Commissioning Mike Hollis (NASA), Frank Lovas (NIST), & Phil Jewell (NRAO)‏ 63rd Ohio State University International Symposium on Molecular Spectroscopy Columbus, OH June 19, 2008

2. 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Presentation Outline http://www.cv.nrao.edu/~aremijan/PRIMOS/ Survey Overview –Scientific Justification –Technical Justification Accessing the data –Reduced data using SLiSE –NRAO archive? Initial Survey Results –Composite spectra –Initial spectral line counts including u-lines Future plans/dynamic scheduling/contacting the working group

3. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Survey Overview A primary focus of current astrobiology research is to investigate our prebiotic molecular origins. As such, over the last several years there have been significant advances in this field primarily due to dedicated searches for large molecules that are possible precursors to molecules of biological importance (biomolecules) in the interstellar medium. There are many specific reasons why a deep spectral line survey is important and timely: 1) In practical terms, a sensitive and methodical survey is one of the most efficient ways to detect new species. 2) Large databases of laboratory spectroscopic transition frequencies exist already (see, RF15). A thorough, sensitive survey would allow astrochemists to utilize these databases to make firm, multi-transition identifications of species. 3) This survey will produce a complete inventory of known interstellar molecules and their transitions and is potentially one of the most important outcomes of this survey. 4) The results will guide further instrumentation development on the GBT.

4. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Survey Overview Source of Interest: SgrB2(N-LMH): The giant molecular cloud complex, Sagittarius B2(N) near the center of our Galaxy, is undoubtedly the preeminent source for the study of large complex interstellar molecules. Of the 141 interstellar molecules detected, more than half have been detected first in the Sagittarius B2 star-forming region. The recent GBT detections of large organic molecules have suggested that prebiotic molecules found toward the SgrB2(N) complex are are extended. Observing Strategy: In the 300 MHz to 50 GHz frequency range of the GBT there is 40.4 GHz of useable bandwidth spread across 16 different receivers. We use the position-switching mode of observation for SgrB2(N-LMH) and switch in azimuth 60 arcminutes off source every two minutes. For low frequency observations using the prime focus (PF), L-band receivers, and some observations at S-Band, we use 4x50 MHz windows for a spectral resolution of ~6.1 kHz. At higher frequencies above S-Band, we use 4x200 MHz windows for a spectral resolution of ~24.4 kHz. In addition, we have performed cursory surveys at Ku, Ka and Q band with 4x800 MHz windows for a spectral resolution of ~390 kHz as a guide to further observations.

5. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH The Green Bank Telescope  B = 740”/ [GHz] 7854 m 2 - ~2 ACRES! At 17 million pounds, it is one of the largest moving structures on land! OFF(2 min)-ON(2 min)‏ 11 new species have been detected with the GBT since 2004

6. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH The National Radio Quiet Zone

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13. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Initial Survey Results

14. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Initial Survey Results

15. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Initial Survey Results

16. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Initial Survey Results

17. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Initial Survey Results

18. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Future Plans To date, we have completed 35 sessions toward Sgr B2N. This corresponds to ~175 hours completed out of 625 approved which is ~28% of the project. Most of the high spectral resolution data yet to be taken is above 20 GHz. We need good weather to complete the spectral line observations at upper K, Ka and Q band properly. This summer, we are experimenting with dynamic scheduling at Q band. The results of these observations should be available next fall. To contact the group: –Anthony Remijan - aremijan@nrao.edu –Mike Hollis – jan.m.hollis@nasa.gov –Frank Lovas – lovas@nist.gov –Phil Jewell - pjewell@nrao.edu Check the website for constant updates on the project including data release, notes, problems and solutions at: http://www.cv.nrao.edu/~aremijan/PRIMOS/

19. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH END Supplementary Slides start below...

20. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Species Detected Towards Sgr B2N with the GBT

21. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Species Detected Towards TMC-1 with the GBT

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23. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Cyclopropenone (c-H 2 C 3 O): A new Interstellar Ring Molecule (Hollis et al. 2006, ApJ, 642, 933)‏ In this work, we identified cyclopropenone (c-H 2 C 3 O), the first keto- ring molecule to be found in an interstellar cloud. Owing to the fact that high stability of c- C 3 H 2 would preserve its skeletal structure in simple reactions and that c- C 3 H 2 is the more abundant interstellar form, the c-H 2 C 3 O that we observe toward Sgr B2(N) may be produced by the gas phase oxygen addition reaction: c-C 3 H 2 + O ---> c-H 2 C 3 O where the divalent carbon accounts for the reactivity of c-C 3 H 2 as shown in the figure to the left.

24. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Hyperfine Structure Identification of Interstellar Cyanoallene toward TMC-1 (Lovas et al. 2006, ApJ, 637, L37)‏ In this work, we identified interstellar cyanoallene (CH 2 CCHCN) using the GBT toward the dark Taurus Molecular Cloud (TMC-1). Cyanoallene and methylcyanoacetylene (CH 3 C 3 N) appear to have a similar abundance toward TMC-1. Barrierless, exothermic chemical reactions of the cyanide radical (CN) with methylacetylene (CH 3 CCH) and CN with allene (CH 2 CCH 2 ) can ultimately lead to the production of C 4 H 3 N isomers: CH 3 CCH + CN ---> CH 2 CCHCN + H CH 3 CCH + CN ---> CH 3 CCCN + H CH 2 CCH 2 + CN ---> CH 2 CCHCN + H CH 2 CCH 2 + CN ---> HCCCH 2 CN + H.

25. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Methyltriacetylene (CH 3 C 6 H) toward TMC-1: The Largest Detected Symmetric Top (Remijan et al. 2006, ApJ, 643, L37)‏ In this work, we identified interstellar methyltriacetylene (CH 3 C 6 H) using the GBT toward the dark Taurus Molecular Cloud (TMC-1). Strong correlations are found among the values of the three different carbon-chain slopes when total column densities of sequence members are plotted against the number of carbon atoms in the carbon chain. This result suggests that the formation chemistry for all these carbon-chain sequences is common.

26. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Detection of Acetamide (CH 3 CONH 2 ): The Largest Molecule with a Peptide Bond (Hollis et al. 2006, ApJ, 643, L25)‏ In this work, we identified interstellar acetamide (CH 3 CONH 2 ) in emission and absorption toward Sagittarius B2(N) by means of four A-species and four E-species rotational transitions. All transitions have energy levels less than 10 K. Since exothermic neutral-radical reactions have been shown be efficient at low temperatures (Herbst 1995), the acetamide observed toward Sgr B2(N) may be produced by the exothermic reaction of formamide with the methylene (CH 2 ) radical: HCONH 2 + CH 2 -> CH 3 CONH 2 This reaction may have an activation barrier because electronic spin is not conserved in the reaction, but such a barrier could be overcome by prevalent large- and small-scale shocks this star- forming region (see Chengalur & Kanekar 2003 and references therein).

27. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH In this work, ketenimine (CH 2 CNH) has been detected in absorption toward SgrB2(N). These ketenimine data show that the hot core at +82 km/s is cooler than the hot core at +64 km/s. Detection of Ketenimine (CH 2 CNH) in SgrB2(N) Hot Cores (Lovas et al. 2006, ApJ, 645, L137)‏ There are at least three feasible reaction mechanisms suggested by experimental and theoretical studies for the formation of ketenimine in the gas phase or on cold surfaces. From the matrix isolation study by Jacox & Milligan (1963) the following reaction was inferred: HCCH + NH -> CH 2 CNH A subsequent matrix isolation study by Jacox (1979) indicates that energy transfer from argon atoms excited in a microwave discharge can convert methyl cyanide to ketenimine shown in the figure above by tautomerization (i.e., an isomerization pathway in which the migration of a hydrogen atom from the methyl group to the nitrogen atom is accompanied by a rearrangement of bonding electrons). Another laboratory investigation of various cyanide species in ices irradiated by UV photons or bombarded by protons showed imine or isonitrile formation (Hudson & Moore 2004). Proton bombardment of pure CH 3 CN ice provided the products ketenimine and CH 3 NC in somewhat lower yield.

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29. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH In the case of acetamide, the model predictions are 6-7 orders of magnitude too low given the low abundances of the starting materials, formamide and acetaldehyde. In general, the observations are continuing to outpace the models.

30. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Future Plans The GBT PRIMOS Project – Searching for our Molecular Origins: www.cv.nrao.edu/~aremijan/PRIMOS Organic Molecules in the ISM – Pilot Study with the Compact Array Broadband Backend (CABB)‏ –Joint observations with the GBT, MOPRA and ATCA Complete 2mm spectral line survey (130-170 GHz) of Sgr B2N, SgrB2 OH, IRC +10 216, Orion KL, W51M, W3 (IRS5)‏ –Barry Turner’s Legacy survey taken between 1993-1995 with the NRAO 12m. www.cv.nrao.edu/Turner2mmLineSurvey

31. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH Stay tuned for the next interstellar molecule...

32. June 19, 2008 63 rd OSU Meeting on Molecular Spectroscopy – Columbus, OH The distribution of CH 3 CN vs. CH 3 NC