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Chemistry in the Central Molecular Zone

Chemistry in the Central Molecular Zone. Jesús Martín-Pintado Centro de Astrobiologia (CAB) Spain. Galactic Center Workshop 2009 19-23 October 2009. Outline of the talk. The Central Molecular Zone Gas and dust properties in the CMZ

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Chemistry in the Central Molecular Zone

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  1. Chemistry in the Central Molecular Zone Jesús Martín-Pintado Centro de Astrobiologia (CAB) Spain Galactic Center Workshop2009 19-23 October 2009

  2. Outline of the talk • The Central Molecular Zone • Gas and dust properties in the CMZ • Heating and chemical complexity in the GC • PhotoDissociation Regions (PDRs) • Shocks • The largest chemical complexity in the Galaxy • Xrays induced chemistry (XDRs) • Chemical complexity templates of CMZ clouds • Diagnostic Diagrams for PDRs • The Circumstellar Disk (CND) • Conclusion & Future prospects

  3. The Central Molecular Zone The inner 500 pc with ~108 M⊙ of mainly molecular gas Average gas density: 100 cm-3 100 times that of the Disk Star Formation Rate: ~0.5M⊙ yr-1 verus 5 M⊙ yr-1 in the Disk Efficiency: 5 10-9 similar to that in the Disk Mopra GC survey ( Burton et al. 2010)

  4. The Central Molecular Zone • The closest center of a galaxy where can only study the physics • In NGC253 0.025” (ALMA) corresponds to 10” in the GC • Difficult to observe the relevant 450 pc (3º) except for CO • Chemical properties at selected positions. Big change Mopra, 30m,.. • The CMZ shows: • Star formation throughout the region (clusters & protoclusters) • Large PDRs illuminated by clusters of massive stars • Strong emission of X-rays (Fe 6.4 keV) and gamma-rays (XDRs) • A massive black hole • Disk-halo interactions: Loops, “tornados”, winds, accretion • Molecular clouds that provide insight into the complicated heating and • chemistry in galactic centers as well as into the feeding of the nucleus The GC provides a unique laboratory for understanding the activities in the heart of the Milky Way as well as in nuclei of galaxies

  5. Comparison with external galaxies ULIRG CMZ is similar to low excitation starburstgalaxies AGN SB GC Data from Genzel et al. (1998) Rodriguez-Fernandez (2005)

  6. Gas and dust properties in the CMZ H2 from ISO Vel. dispersion [kms-1] 15 – 30 ≤5 Mean Gas Density [cm-3]∼104--5 ∼102-3 Magnetic Field [mG] ~ mG ≤ 0.1 12 C/13C ratio ∼ 25 ∼ 75 Dust: cold component ~15 K warm component 27- 42 K Gas temperatures: 15-500 K (NH3 & H2) (Güsten et al.1981, Morris et al.1983 and Huttermesiter et.al. 1993) Tgas >Tdust in starburst galaxies Mauersberger et al. (2003)‏ What is the domiant heating Mechanism? UV radiation, Xrays, shocks, Cosmic rays? Rodriguez-Fernandez et al.(2000, 2001,2004)

  7. Photodissociation Regions (PDRs) H2 pure rotational lines and atomic fine structure lines ISO: Rodriguez-Fernandez et al.(2000, 2001 and 2004) andSPITZER: Simpson et al. (2007) Gas temperature of ~150-500 K H2 at ~150 K: few 1022 cm-2H2 at ~500 K: few 1021 cm-2 Gas at >150 K is 30% of total C-shock or PDR explain the temperatures PDRs (n~103 cm-3, FUV~103 Go)‏ Consistent with the fine structure lines But not the intensities Several PDRs and/or C-shocks ISO fine strucuture lines C-Shock from Draine et al. (1983) J-Shock from Hollenbach & McKee (1989) Posters 6, 8 and 39

  8. C-shocks versus PDRs(Chemistry) NH3 Hüttemeister et al. (1993), Martin-Pintado et al. (1999) • NH3 is photodissociated in PDRs • and enhanced by shocks • Large NH3 abundance, ~ 10-7 • at ~ 150 K and at ~ 20 K • C-shocks: Origin of the shocks? • Expanding shells (6-10 km/s) • Sizes 1-2,5 pc • Powered by evolved massive • Supernovae • W-R stars. Chemistry? Sgr B2 NH3 (3,3) VLA 300 shells in the CO survey by Hasegawa et al. (1998)‏, Oka et al. (1997),...

  9. Largescale shocks (SiO Chemistry) Martin-Pintado et al. (1997) , (2000) and Hüttemeister et al. (1998), SiO is one of the best tracers of shocks In the CMZ, large SiO abundance >10-9 Bar potential dynamics (cloud-cloud collisions). SiO J=1-0

  10. Largescale shocks Gas in the CMZ responds to the bar potential CO Tansfer of molecular gas from X1 to X2 Gas inflow(Binney et al. 1991)‏ Supported by 12C/13C isotopic ratios: X2 ~30 but X1 ~60 (Poster 37) However also outflowing gas “Molecular Tornado” (Soufe et al 2007) Bissantz et al. (2003)‏

  11. The largest Chemical Complexity IRAM+GBT data Requena-Torres et al.(2006) and (2008) CMZ typical clouds Largest abundance of Complex Organic Molecules in the galaxy Similar ice mantles Formation of COMs • Grain chemistry • Hydrogenation • Cosmic Raysys FREQUENT SHOCKS Origin?: Turbulence Poster 15

  12. Origin of the Fe 6.4 keV line unclear (see e.g. Koyama et al. 2008) Two scenarios: XRN (Koyama et al. 1996), LECRs (Yusef-Zadeh et al.(2007) Molecular column density correlated wih the Fe 6.4 Kev (Tsuboi et al. 1999) X-ray Dominated Regions XDRs as traced by the Fe 6.4 kev line Chandra image SiO/CS correlated with the Fe 6.4 keV. XDr chemistry? Martin-Pintado et al. (2000) Amo-Balandron et al. (2009)

  13. XDRs and SiO chemistry Gas-phase: XDR chemistry :FX ~0.01-0.06 erg/cm2sand NH2=(0.6-2.7)·1022 cm-2 Models: Meijerink & Spaans (2005) 100 times larger than in the GC SiO/CS ratios cannot be explained by the models Grains: Low Energy cosmic rays:Likely the 6.4 keV line Need large 1024 column densities and efficient grain erosion Combined with SNe to produce the enhanced SiO abudance X-ray reflection nebulae illuminated by a flare(s) from Sgr A Needsalso the evaporation of VSG of ~10 A Need to study specific tracers like HCO, HOC+, CO+, .. but also PDRs Posters 16, 20 and 47

  14. Chemical complexity templates S. Martin et al. (2004), (2005)‏ IRAM 30m Mopra 13 surveys 2 mm window 3 mm window Martin et al, 2007 GC typical GC PDR

  15. Diagnostic diagram for PDRs Martin et al. (2008) PDRs: Large abundance changes HNCO & CH3OH ↓↓ Not included in models CS ↑↑ UV does not dominate the heating (chemistry)‏ Hot cores

  16. Picture for typical clouds in the CMZ Large complexity: CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH CH3OH HNCO C2H5OH CS , CH3OH HNCO C2H5O CS , CH3OH HNCO C2H5OH CS CH3OH HNCO C2H5OH CS CH3OH HNCO C2H5O CS , CH3OH HNCO C2H5O CS , CH3OH HNCO C2H5OH CS

  17. Picture for typical clouds in the CMZ Large complexity: CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH PDRs: destroy HNCO and produce CO+, HOC+, HCO CH3OH HNCO C2H5OH CS , CH3OH HNCO C2H5O CS , CH3OH HNCO C2H5OH CS CS CH3OH HNCO C2H5O CS , Effects of the clusters: HNCO/CS gradient CS , CH3OH HNCO C2H5OH CS

  18. The Circumnuclear Disk (CND) Dense neutral and ionized gas surrounding Sgr A* Ring-like: Inner radius of 1.5 pc (ionized gas) and outer edge 3 pc The central cluster in inside the CND. UV from stars >> photodissociation SMA HCN(4-3) Montero-Cataño (2007) Amo-Baladro et al. (2009) GMCs CND Position Poster27 Velocity HNCO is photodissociated in the CND with a gradient to the clouds

  19. The activity in the CMZ offers a unique possibility for understanding the processes that dominates the heating, the chemistry and the star formation in the nuclei of galaxies • Chemical complexity has the potential to trace the heating mechanics: • UV radiation is important but likely does not dominante the heating: • Tracers: FIR fine structure lines, HNCO, H2, NH3 ,.. (HCO, HOC+,.?) • Shocks seem to dominate the heating, but their origin(s) are unclear • Large scale (accretion, ejection), SNe, stellar winds, turbulence (MHD?) • Tracers: SiO, HNCO, HN3, Complex Organic Molecules... (?) • X-rays induced chemistry is yet unclear: SiO/CS might trace it. • Role of Cosmic Rays (CR) is unclear. CR induced chemistry is promising Conclusions

  20. Future prospects • A multiwavelength approach is fundamental to make substantial progress • We are at the beginning of a golden age of molecular astrophysics: • New high sensitivity wideband receivers at cm and mm submm wavelengths will provide “high angular resolution” unbiased mapping of the CMZ+halo • e-VLA and ALMA will also provide very high resolution unbiased imaging • Herchel and SOFIA will provide fine structure lines and high excitation molecular line images. • More powerful set of molecular diagnostics tools for XDRs, PDRs, Shocks,. will emerge

  21. VLA (0.1”) v7 J=5-4 Protoclusters of massive stars Figer et al. (2004) S. Martin et al. (2005) and thesis Sgr B2N 0.1 7 Sgr B2N PdBI (6”) De Vicente et al. (1993)‏ HC3N* v7, v6, v5, T ~ 300 K L ~107 Lo Condensations with L ~105 Lo Protocluster: IMF? Merging possible?

  22. Expanding bubbles (shock Chemistry)‏ SiO 30-m Requena-Torres et al. (2010)‏ Sgr B2 IRAM 30-m SiO best tracer of shocks Enhanced by 106 due to: grain disruption VLA

  23. Chemical ComplexityThe role of CH3CH2OH in Ancient China Ox-shaped Zun (wine vessel) Gong (wine vessel) Square Yi (wine vessel) of Shi Yi

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