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Paola Caselli School of Physics and Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES

Paola Caselli School of Physics and Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES. ISM science cases with Band 11. Graves, Richers 2013. Outline. Diffuse clouds and PDRs Dense clouds Shocked regions Young protoplanetary disks. The Herschel legacy.

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Paola Caselli School of Physics and Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES

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  1. Paola Caselli School of Physics and Astronomy FACULTY OF MATHEMATICS & PHYSICAL SCIENCES ISM science cases with Band 11 Graves, Richers 2013

  2. Outline • Diffuse clouds and PDRs • Dense clouds • Shocked regions • Young protoplanetary disks

  3. The Herschel legacy Herschel Space Observatory FIR (51 - 671 μm) -3.5 m dish, HPBW ~ 9´´ - 47´´ –3 focal plane science instruments: SPIRE (194-671m, FOV 4´8´, /~3) PACS (51-220m, FOV 47´´47´´, /~1000-3000) HIFI (157-615m, / up to 107)

  4. Diffuse gas / PDRs e.g. Gerin et al. 2010, Godard et al. 2011, Persson et al. 2012, Flagey et al. 2013

  5. Diffuse gas / PDRs • How well do we understand the formation of molecules ? (reaction networks ? Reaction rates ?) • What is the impact of turbulence on chemistry ? • How can we use molecular lines to understand the properties of the diffuse ISM and its evolution towards denser gas (formation of giant molecular clouds) ? From Gerin 2012

  6. Hydrides Diffuse gas • the first chemical steps starting from atomic gas • at the root of interstellar chemistry • diagnostics of physical/chemical processes From Gerin 2012

  7. Gerin et al. 2012

  8. Gerin et al. 2012

  9. Detection of hydrides toward the high mass YSO W3 IRS 5 (Benz+ 2010; Bruderer+ 2010). New molecules: OH+,H2O+, SH+. H2O+/H2O from 0.01 to > 1 (Wyrowski+2010). H2O+ velocity matches that of the [CII] and OH lines (Ossenkopf+ 2010)

  10. What can we do with Band 11? • Disentangle between contribution from interstellar medium and star forming region. Clues on various velocity components. • Which species? Needed transitions from low energy levels. • CH (tracer of diffuse molecular material, but also high density) • OH+ (tracer of cosmic-ray ionization rate) • NH • ND • NH+ (not detected) • NH2 • SH (detected with SOFIA/GREAT; Neufeld et al. 2012) • SH+ (tracer of Turbulent Dissipation Regions, TDRs, Gerin et al. 2012 in diffuse molecular clouds; or warm – 500-1000 K – gas in dense PDRs; Nagy et al. 2013).

  11. What can we do with Band 11? Image high excitation molecular lines of simple rotors in PDRs Pilleri et al. 2012

  12. Nitrogenchemistry in dense clouds <<Nitrogen hydrates in the cold envelope of IRAS16293-2422>> Hily-Blant et al. 2010 NH:NH2:NH3 ~ 5:1:300 [ 1:10:100 towards Sgr B2; Goicoechea et al. 2004 ] NH is under-predicted by more than an order of magnitude NH2 + O  OH + NH Unless NH can be formed by N2H+ + e .. o-NH2

  13. Nitrogen chemistry: NH, NH2 Dislaire et al. (2012) propose a new rate for the reaction which initiates the formation of nitrogen hydrides: N+ + H2  NH+ + H which depends on the ortho-to-para H2 ratio. This new rates reconcile theory with observations toward IRAS 16293-2422 provided that NH can still form upon dissociative recombination of N2H+. If this is the case, previous work has overestimated the low-temperature rate coefficient with o-H2 by almost 3 orders of magnitudes (cf. Le Bourlot 1991)…

  14. Nitrogen chemistry: NH, NH2 BUT…. Persson et al. (2010, 2012) find NH:NH2:NH3 ~ 2:1:1 in diffuse clouds (very different from what observed in dark clouds and difficult to explain with chemical models !). + a low ortho-to-para NH3 ratios (0.5-0.70.1), which cannot be explained by current models. <<Some laboratory evidence exists that dissociative recombination reactions have different rate coefficients depending upon the nuclear spin configuration of the molecular ion.>> --needed more work!

  15. Nitrogen chemistry: ND First detection of ND! ND [ND]/[NH] ~ 0.3-1.0 ! Possible routes: NH + H2D+ NHD+ + H2 N+ + HD  ND+ + H Bacmann et al. 2010

  16. What can we do with Band 11? • Follow up Herschel work and investigate nitrogen chemistry and light hydrides in other Class 0 sources. • Which species? Needed transitions from low energy levels. • NH • ND • NH+ (not detected) • NH2 • + • para-H2D+ @ 1370 GHz (ortho-H2D+@ 372 GHz; Caselli+ 2003) • ortho-D2H+ @ 1476 GHz (para-D2H+ @ 692 GHz; Vastel+ 2004)

  17. The importanceof H3+isotopologues in dense cores: gas-phase and surfacedeuteration, ionizationfraction Pagani, Vastel et al. 2009 Vastel et al. 2012

  18. Observations of ortho and para H2D+ and D2H+ will help to constrain the ortho-to-para H2 ratio, crucial to set the age of dense clouds (e.g. Pagani et al. 2011). Kong, Caselli, Tan & Wakelam, in prep.

  19. What can we do with Band 11? • ACA + ALMA (beam of 1.6 arcsec). • Targets: envelopes of Class 0 sources. • Expected THz continuum fluxes ~ a few - 10 Jy (Td ~ 30 – 50 K). • From previous H2D+ and D2H+ observations, τ ~ 0.3 for both ground state THz lines, implying |Tb-Tc| ~ 0.3 – 0.8 K . • Considering a sensitivity of 0.4 K (1 hour integration time), with velocity resolution 0.5 km/s, the detection of the para-H2D+ and ortho-D2H+ can be obtained after a few hours integration time toward hot corinos (PWV ~ 100 μm).

  20. What can we do with Band 11? The structure of the central 1000 AU of pre-stellar cores (PSCs) with THz dust continuum observations: toward disk formation. Caselli 2011

  21. What else can we do with Band 11? View the cavity walls of outlfows (with, e.g. high J-CO lines: 9-8, 11-10, 12-11, 13-12; and/or light hydrides, e.g. Bruderer et al. 2010) and assess the importance of shock/UV heating. Important for theory ! (see Sylvie’s Talk) Courtesy of Lars Kristensen

  22. What else can we do with Band 11? Resolve the region observed in CO(9-8) with Herschel toward massive pre-stellar cores, to locate shocked gas, which may be produced by turbulence decay in the process of core formation. H2O(110-101) OT2 data Caselli et al., in prep. Pon et al., in prep.

  23. The dawn of protoplanetary disks Caselli & Ceccarelli 2012 Boley 2009 Ileeet al. 2011

  24. Douglas et al. 2013, in prep. CASA simulation of ALMA observations of dust continuum emission at 300 GHz of a 0.39 M self-gravitating protoplanetary disks around 1M star (hydrodynamical simulation of Boley et al. 2009). With Band 11: possibility to resolve spiral structure for less massive disks.

  25. Summary • Light hydrides in absorption toward massive star forming regions to locate the absorbing gas + High excitation lines in PDRs. • The building blocks of nitrogen chemistry and deuterium fractionation toward Class 0 sources + THz continuum imaging of PSCs. • High J CO lines, light hydrides to resolve the outflow cavity walls and shocked gas in forming clouds, to study the importance of UV/shock heating. • THz continuum imaging, to resolve the predicted spiral structure and test the theory. Diffuse clouds / PDRs Dense clouds Shocked regions Young protoplanetary disks

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