Prebio'c molecules of interest to SKA. Per Bergman Onsala Space Observatory

Transcription

1 Prebio'c molecules of interest to SKA Per Bergman Onsala Space Observatory

2 Prebio'c molecules Amino acids and their (possible) precurors Building blocks for proteins What do we know about the forma'on under interstellar condi'ons? Are they detectable? Some other molecules of interest Glycine isomers Molecules with pep'de bonds

3 Amino acids Name Mass Formula Glycine 75 C 2 H 5 NO 2 M Alanine 89 C 3 H 7 NO 2 M Serine 105 C 3 H 7 NO 3 Proline 115 C 5 H 9 NO 2 M Valine 117 C 5 H 11 NO 2 M Threonine 119 C 4 H 9 NO 3 (Iso)Leucine 131 C 6 H 13 NO 2 M Asparagine 132 C 4 H 8 N 2 O 3 Glutamine 146 C 5 H 10 N 2 O 3 amino group - NH 2 Lysine 146 C 6 H 14 N 2 O 2 His'dine 155 C 6 H 9 N 3 O 2 carboxyl group - COOH Phenylalanine 165 C 9 H 11 NO 2 Arginine 174 C 6 H 14 N 4 O 2

4 Mechanisms of forma'on Strecker synthesis (reac'on in liquid water) of HCN, NH 3, aldehydes (RCHO) in meteori'c parent bodies (e.g. Peltzer & Bada 1978) some observed isotopic enrichment - > interstellar origin of the precursor molecules the observed deuterium frac'ona'on is not what would be expected from the Strecker synthesis (Lerner 1997) In gas- phase via ion- molecule reac'ons (Chakrabar' & Chakrabar' 2000) probably rather incomplete reac'on network UV irradia'on of interstellar ice analogs (e.g. Elsila et al. 2007, Lee et al. 2009) ice containing: H 2 O, CH 3 OH, HCN, NH 3 - > short life'me (in gas phase) due to UV radia'on (Ehrenfreund et al. 2001) - > taken together: it is simply not known where and how they are formed - > probably a combina'on of the laber two mechanisms

5 SKA1- mid Band 5 proper'es used for predic'ons No of antennas: 190 Frequency range: GHz Beam area at 1 GHz: 1.56 arcmin^2 Beam: 8.5 arcsec at 10 GHz SEFD: 2.8 Jy Numbers taken from Tables 6 & 7 in SKA- TEL- SKO- DD BaselineDesign1 (hbp://

6 Glycine I, emission Observed 3σ limits: N < (3-10)x10 13 cm - 2 (Combes et al. 1996, Hollis et al. 2003) Spectroscopy: CDMS (Müller et al 2005), Lovas et al. 1995, Ilyushin et al. 2005

7 Glycine I, absorp'on

8 Sgr B2 cm con'nuum Values from Hollis et al. (2007) are used to es'mate absorp'on against Sgr B2(N) Source size: θ S = 143 (ν/1 GHz) Flux density: S Jy = 14 (ν/10 GHz) - 0.7

9 Glycine I, Sgr B2 (N) absorp'on

10 α- alanine I, emission Spectroscopy: CDMS (Müller et al. 2005), Blanco et al. 2004, Godfrey et al. 1993, Hirata et al. 2008

11 α- alanine I, absorp'on

12 α- alanine I, Sgr B2 absorp'on

13 Isomers to glycine NH 2 CH 2 COOH It is not the most stable isomer (Labelais et al. 2011). These are more stable and argued to be the most abundant: N- methyl carbamic, CH 3 NCH(O)OH Microwave rota'onal spectroscopy? Methyl carbamate CH 3 OC(O)NH 2 JPL (+ Groner et al. 2007)

14 Methyl carbamate, emission Spectroscopy: JPL (Pickeb et al. 1998), Ilyushin et al. 2006, Marstokk et al. 1999, Bakri et al P. Bergman SKA CoL Nov

15 Methyl carbamate, absorp'on P. Bergman SKA CoL Nov

16 Methyl carbamate, Sgr B2 absorp'on P. Bergman SKA CoL Nov

17 SKA1- mid Band 5 detectability of glycine (+isomers) and α- alanine Emission (T=10 K, beam ~ 8 arcsec at 10 GHz): S/N ~ 0.02 (<N>/10 13 cm - 2 ) (t/1 hr) 0.5 or for S/N = 5 t hrs ~ (10 13 cm - 2 /<N>) 2 Absorp'on against Sgr B2 (T=10 K, beam ~ 8 arcsec at 10 GHz): S/N ~ 0.08 (<N>/10 13 cm - 2 ) (t/1 hr) 0.5 or for S/N = 5 t hrs ~ 3900 (10 13 cm - 2 /<N>) 2

18 Carbamic acid, NH 2 COOH Formally the simplest amino acid, but is highly unstable under terrestrial condi'ons NH 2 COOH - > NH 3 + CO 2 Thought to be produced from urea in living systems No rota'onal lab spectroscopy? (IR spectroscopy & structure: Khanna & Moore 1999) amino group - NH 2 carboxyl group - COOH Glycine

19 Molecules with pep'de bonds: Formamide, HCONH 2 Acetamide, CH 3 CONH 2 Urea/Carbamide, NH 2 CONH 2

20 Formamide, HCONH 2, emission

21 Formamide, HCONH 2, absorp'on

22 Formamide, HCONH 2 First detec'on 1971 (Rubin et al. 1971), extragalac'c (Muller et al. 2013) Typical column densi'es (Nummelin et al. 2000, Hollis et al. 2006, Bisschop et al. 2007, Halfen et al. 2011, Adande et al. 2013) SgrB2(N): (4-6)x10 14 cm - 2 Orion KL: 9x10 13 cm - 2 GMCs: (1-90)x10 12 cm - 2 Hollis et al 2006, ApJ 643, L25

23 Formamide, HCONH 2, Sgr B2 absorp'on

24 Acetamide, CH 3 CONH 2 Detected toward Sgr B2 (Hollis et al. 2006) with a column density of of that of formamide, i.e. about 2x10 14 cm- 2 Spectroscopy: Suenram et al. 2001, Ilyshin et al Not (yet?) in JPL or CDMS Possible forma'on with exothermic reac'on of formamide with methylene radical HCONH 2 + CH 2 - > CH 3 CONH 2 Hollis et al ApJ 643, L25

25 Urea, emission Spectroscopy: Brown et al. 1975, JMS 58, 445

26 Urea, Sgr B2 absorp'on

27 Summary Glycine (and α- alanine) would be less difficult detect in absorp'on against a strong con'nuum source (Sgr B2) but it would s'll require (of the order of) a few thousand hrs just to improve (by a factor of ~5) current limits Two of the glycine isomers are likely to be more abundant. Pep'de bond molecules like formamide (and perhaps even urea) are much easier to detect in various sources low temperature is favourable

28 Aminoacetonitrile, H 2 NCH 2 CN Hydroxyacetonitrile, HOCH 2 CN H 2 CO + HCN - > HOCH 2 CN HOCH 2 CN + H 2 O - > C 2 H 5 NO 2

29 Aminomethyl radical, CH 2 NH 2 CH 2 NH 2 + HOOC - > C 2 H 5 NO 2 Carbamic acid, CH 3 NO 2

30 Nucleo'de bases Name Mass Formula Cytosine 111 C 4 H 5 N 3 O Uracil 112 C 4 H 4 N 2 O 2 Thymine 126 C 5 H 6 N 2 O 2 Adenine 135 C 5 H 5 N 5 Guanine 151 C 5 H 5 N 5 O