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Prebiological Molecules in the ISM

Prebiological Molecules in the ISM. T. L. Wilson ALMA. What are prebiological molecules?. If use Miller-Urey experiment, can consider ammonia, methane, carbon dioxide, water, etc. are “prebiological” These are all found in the Interstellar Medium, but at low concentrations compared to earth

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Prebiological Molecules in the ISM

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  1. Prebiological Molecules in the ISM T. L. Wilson ALMA Astrobio2010

  2. What are prebiological molecules? • If use Miller-Urey experiment, can consider ammonia, methane, carbon dioxide, water, etc. are “prebiological” • These are all found in the Interstellar Medium, but at low concentrations compared to earth • In the following will consider only gas phase species, since these identifications are rather unique • This is not the case for some species that are condensed on grains (i.e. PAH’s) Astrobio2010

  3. Sketch of Protostar Development All phases are important, but two very relevant stages are Class 0 and and Class II. These will be addressed in the following talks. 5

  4. Number of Species Found Astrobio2010

  5. Astrobio2010

  6. Structure of Some Species These are asymmetric top molecules which have many transitions in the millimeter range in warm sources Astrobio2010

  7. The Ground State of Water Vapor See talk by Bill Dent

  8. But not the most sought after: Glycine (simplest amino acid). This has not been conclusively found, so far. Shown on the right are the three confimers. Astrobio2010

  9. Orion KL Spectrum from Ground See talk by Cecile Favre 11 Astrobio2010

  10. A Typical Set of Numbers • In the 3 mm range, at a frequency of ~100 GHz, the limit of a fractional abundance of Glycine is reportedly <10-11 of the abundance of molecular hydrogen. This is based on a total column density of 5 to 7 1013 cm-2of Glycine. The authors comment that the search is affected by confusion, that is, overlapping spectral lines of other species. • Can we do better? Yes! Expect the Glycine region to be small. • The beam size of this search was 30”. With Plateau de Bure, obtained 3”, or a factor of 100 times better angular resolution, but the limit to column density was 100 times worse, 1015 cm-2. With ALMA will have at least 10 times better sensitivity. Astrobio2010

  11. How Can we Do Better? • Improve the angular resolution to pick out regions where specific species are located • Measure all spectral lines from a species with many lines and remove these from the observed spectra • Find sources that are more favorable for searches for specific species (i.e. narrower line widths) Astrobio2010

  12. See talk By Cecile Favre Orion Hot Core Astrobio2010

  13. ALMA: The Future of mm/sub-mm Astronomy • A global project that will revolutionize the field • “a picture is worth a million simulations” • The scientific goals encompass much of astronomy • Especially prominent will be the study of star formation, interstellar chemistry, and structure of molecular clouds. • In addition will enhance the study of comets, our planets, and high redshift sources. Astrobio2010

  14. Location Chajntantor Plateau at 5000m in northern Chile ALMA ETH Seminar

  15. Bilateral ALMA + ALMA Compact Array (in lower right) Astrobio2010

  16. The ALMA FOV is 25” at 1 mm ALMA Receiver Bands Astrobio2010

  17. Astrobio2010

  18. Sensitivity of ALMA

  19. Correlator Set Up: Four IF Bands of 2 GHz Each Can be Analyzed by 32 Filters, 16 in Each Polarization Region analyzed by a single spectrometer (we show ½ of the filters) 2 GHz wide IF Spectrometer has 8192 channels Astrobio2010

  20. ALMA Timeline • CSV starting in a few weeks • 20 months later is the start of Early Science with at least 16 antennas (of the 66 planned) • 4 receiver bands (3, 1.3, 0.8 0.6 mm wavelength) • Full spectrometer capability • Data reduction and Observing Tools for users • ALMA Regional Centers to help users in North America, Europe and East Asia

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