Prebio,c molecules of interest to SKA

Prebio'c molecules of interest to SKA Per Bergman Onsala Space Observatory 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 P. Bergman SKA CoL Nov 7 2013 Amino acids Name Mass Formula Glycine 75 C2H5NO2 M Alanine 89 C3H7NO2 M Serine 105 C3H7NO3 Proline 115 C5H9NO2 M Valine 117 C5H11NO2 M Threonine 119 C4H9NO3 (Iso)Leucine 131 C6H13NO2 Asparagine 132 C4H8N2O3 Glutamine 146 C5H10N2O3 Lysine 146 C6H14N2O2 His'dine 155 C6H9N3O2 Phenylalanine 165 C9H11NO2 Arginine C6H14N4O2 174 P. Bergman SKA CoL Nov 7 2013 M amino group -­‐NH2 carboxyl group -­‐COOH Mechanisms of forma'on •  Strecker synthesis (reac'on in liquid water) of HCN, NH3, 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: H2O, CH3OH, HCN, NH3 -­‐> 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 P. Bergman SKA CoL Nov 7 2013 SKA1-­‐mid Band 5 proper'es used for predic'ons •  No of antennas: 190 •  Frequency range: 4.6-­‐13.8 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-­‐001-­‐1.BaselineDesign1 (hbp://www.skatelescope.org/?abachment_id=5400) P. Bergman SKA CoL Nov 7 2013 Glycine I, emission Observed 3σ limits: N < (3-­‐10)x1013 cm-­‐2 (Combes et al. 1996, Hollis et al. 2003) Spectroscopy: CDMS (Müller et al 2005), Lovas et al. 1995, Ilyushin et al. 2005 P. Bergman SKA CoL Nov 7 2013 Glycine I, absorp'on P. Bergman SKA CoL Nov 7 2013 Sgr B2 cm con'nuum •  Values from Hollis et al. (2007) are used to es'mate absorp'on against Sgr B2(N) •  Source size: θS = 143” (ν/1 GHz)-­‐0.52 •  Flux density: SJy = 14 (ν/10 GHz)-­‐0.7 P. Bergman SKA CoL Nov 7 2013 Glycine I, Sgr B2 (N) absorp'on P. Bergman SKA CoL Nov 7 2013 α-­‐alanine I, emission Spectroscopy: CDMS (Müller et al. 2005), Blanco et al. 2004, Godfrey et al. 1993, Hirata et al. 2008 P. Bergman SKA CoL Nov 7 2013 α-­‐alanine I, absorp'on P. Bergman SKA CoL Nov 7 2013 α-­‐alanine I, Sgr B2 absorp'on P. Bergman SKA CoL Nov 7 2013 Isomers to glycine NH2CH2COOH •  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, CH3NCH(O)OH •  Microwave rota'onal spectroscopy? –  Methyl carbamate CH3OC(O)NH2 •  JPL (+ Groner et al. 2007) P. Bergman SKA CoL Nov 7 2013 Methyl carbamate, emission Spectroscopy: JPL (Pickeb et al. 1998), Ilyushin et al. 2006, Marstokk et al. 1999, Bakri et al. 2002 P. Bergman SKA CoL Nov 7 2013 Methyl carbamate, absorp'on P. Bergman SKA CoL Nov 7 2013 Methyl carbamate, Sgr B2 absorp'on P. Bergman SKA CoL Nov 7 2013 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>/1013 cm-­‐2) (t/1 hr)0.5 or for S/N = 5 thrs ~ 60000 (1013 cm-­‐2/<N>)2 •  Absorp'on against Sgr B2 (T=10 K, beam ~ 8 arcsec at 10 GHz): S/N ~ 0.08 (<N>/1013 cm-­‐2) (t/1 hr)0.5 or for S/N = 5 thrs ~ 3900 (1013 cm-­‐2/<N>)2 P. Bergman SKA CoL Nov 7 2013 Carbamic acid, NH2COOH •  Formally the simplest amino acid, but is highly unstable under terrestrial condi'ons •  NH2COOH -­‐> NH3 + CO2 amino group -­‐NH
•  Thought to be produced from urea in living systems •  No rota'onal lab spectroscopy? •  (IR spectroscopy & structure: Khanna & Moore 1999) P. Bergman SKA CoL Nov 7 2013 carboxyl group -­‐COOH 2 Glycine Molecules with pep'de bonds: Formamide, HCONH2 Acetamide, CH3CONH2 Urea/Carbamide, NH2CONH2 P. Bergman SKA CoL Nov 7 2013 Formamide, HCONH2, emission P. Bergman SKA CoL Nov 7 2013 Formamide, HCONH2, absorp'on P. Bergman SKA CoL Nov 7 2013 Formamide, HCONH2 •  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)x1014 cm-­‐2 –  Orion KL: 9x1013 cm-­‐2 –  GMCs: (1-­‐90)x1012 cm-­‐2 Hollis et al 2006, ApJ 643, L25 P. Bergman SKA CoL Nov 7 2013 Formamide, HCONH2, Sgr B2 absorp'on P. Bergman SKA CoL Nov 7 2013 Acetamide, CH3CONH2 •  Detected toward Sgr B2 (Hollis et al. 2006) with a column density of 0.1-­‐0.5 of that of formamide, i.e. about 2x1014 cm-­‐2 •  Spectroscopy: Suenram et al. 2001, Ilyshin et al. 2004 –  Not (yet?) in JPL or CDMS •  Possible forma'on with exothermic reac'on of formamide with methylene radical HCONH2 + CH2 -­‐> CH3CONH2 P. Bergman SKA CoL Nov 7 2013 Hollis et al. 2006 ApJ 643, L25 Urea, emission Spectroscopy: Brown et al. 1975, JMS 58, 445 P. Bergman SKA CoL Nov 7 2013 Urea, Sgr B2 absorp'on P. Bergman SKA CoL Nov 7 2013 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 P. Bergman SKA CoL Nov 7 2013 Aminoacetonitrile, H2NCH2CN Hydroxyacetonitrile, HOCH2CN H2CO + HCN -­‐> HOCH2CN HOCH2CN + H2O -­‐> C2H5NO2 P. Bergman SKA CoL Nov 7 2013 Aminomethyl radical, CH2NH2 CH2NH2 + HOOC -­‐> C2H5NO2 Carbamic acid, CH3NO2 P. Bergman SKA CoL Nov 7 2013 Nucleo'de bases Name Mass Formula Cytosine 111 C4H5N3O Uracil 112 C4H4N2O2 Thymine 126 C5H6N2O2 Adenine 135 C5H5N5 Guanine 151 C5H5N5O P. Bergman SKA CoL Nov 7 2013