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

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) Polyaromatic hydrocarbons=PAH’s Astrobio2010

Different types of MC’s, dark clouds are colder Different types of MC’s, dark clouds are colder. PDR=Photon Dominated Region. Most of the MC’s consist of molecular hydrogen that has no spectral lines if T is low.

The dust and molecules appear in emission in mm/sub-mm dust

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

Number of Species Found The chemistry in the ISM is more general than that found on earth in the sense that the conditions are more variable Astrobio2010

The chemistry of the ISM is more general than on earth, since ion-molecule reactions, and other processes are operating. However, all follows the rules of quantum mechanics. Astrobio2010

Structure of Some Species These are asymmetric top molecules which have many transitions in the millimeter range in warm sources From the top: Methanol, methyl formate, dimethyl ether Astrobio2010

The Ground State of Water Vapor See talk by Bill Dent

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. NH_2CH_2COOH is chemical formula of Glycine Astrobio2010

Orion KL Spectrum from Ground This illustrates the spectral line confusion. See talk by Cecile Favre 11 Astrobio2010

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-2 of 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. 30m beam is 20,000 AU. ALMA and PdeB get 1,000 AU. This is still the average over our entire soalr system. Astrobio2010

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

Orion Hot Core See talk By Cecile Favre Astrobio2010 Methyl Formate in (a), ethyl alcohol in (b), dimethyl ether in (c), and Vinyl Cyanide in (d). Astrobio2010

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. A Next Generation Millimeter Telescope A major step in astronomy  a mm/submm equivalent of VLT, HST, JWST, EVLA Capable of seeing star-forming galaxies across the Universe Capable of seeing star-forming regions across the Galaxy These Objectives Require: An angular resolution of 0.1” at 3 mm A collecting area of about 6,000 sq m An array of antennas to obtain arc sec or better angular resolution A site which is high, dry, large, flat since water vapor abso- a high Andean plateau is idealrbs mm/sub-mm signals Astrobio2010

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

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

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

Astrobio2010

Sensitivity of ALMA Astrobio2010

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

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