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)
Polyaromatic hydrocarbons=PAH’s
Astrobio2010

3. 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.

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

5. 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

6. 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

7. 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

8. 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

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

10. 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

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

12. 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 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

13. 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

14. 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

15. 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

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

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

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

19. Astrobio2010

20. Sensitivity of ALMA
Astrobio2010

21. 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

22. 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, 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