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ALMA and ISM / Star Formation

ALMA and ISM / Star Formation. St é phane GUILLOTEAU Observatoire de Bordeaux. What’s new with ALMA ? (compared to current mm arrays). A fast instrument  surveys become possible A sensitive instrument  weak lines, small objects become accessible

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ALMA and ISM / Star Formation

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  1. ALMA and ISM / Star Formation Stéphane GUILLOTEAU Observatoire de Bordeaux DUSTY04 – Paris

  2. What’s new with ALMA ? (compared to current mm arrays) • A fast instrument  surveys become possible • A sensitive instrument  weak lines, small objects become accessible • High angular resolution  details of star formation • Wide field imaging with ACA from large to small scales • Wide frequency coverage wide range of physical conditions can be adressed • Polarisation • But a large survey, at high angular resolution, in full polarisation, over arcmin scales, in several lines, would take forever Choices will have to be made S.Guilloteau – ISM & Star Formation

  3. Star Formation Physics • Initial mass function from large scale surveys (gas + dust images) • Polarization: the role of magnetic fields • Complete samples in several types of star-forming regions • Velocity field (accretion) in envelopes of Class 0 protostars • (non)-Keplerian disks around YSOs: • Star masses from disk kinematics • Evolutionary tracks of proto / PMS stars • Evolutionary status of disks • Planet formation • Binarity (70 %): gas + dust distribution, tidal truncation of inner / outer disks S.Guilloteau – ISM & Star Formation

  4. Structure of the ISM • Mosaics of a few arcmin squared, at angular resolution of 0.4 to 2”, could reveal the filamentary structure of the ISM (e.g. Pety & Falgarone 2004) • High spectral resolution required to reveal non Gaussian line wings which trace turbulence • What is the inner scale of the turbulence cascade ? • Chemistry in shocked regions or vortices? Several molecular lines required S.Guilloteau – ISM & Star Formation

  5. Initial Conditions of Star Formation • The link between condensations and IMF (Motte et al 1998) • Can be extended to much lower masses, and/or very different environments (e.g. High mass star forming regions) S.Guilloteau – ISM & Star Formation

  6. Initial Conditions of Star Formation • Density and temperature gradients in starless cores • Molecular chemistry of cloud cores: depletion and deuteration • Searching for infall motions (e.g. Di Francesco et al 2001). Beware of interferometer filtering (Gueth et al 1997) S.Guilloteau – ISM & Star Formation

  7. Massive Stars • Formation by collapse or merging ? • High angular resolution of massive protostars may help solving this issue • Proper motions studies may be needed very high angular resolution + long term monitoring • Will outflow contaminate the picture (Beuther et al 2004) S.Guilloteau – ISM & Star Formation

  8. Fragmentation & Multiplicity • Example from Looney et al 1997 • Small number of proto-binaries detected so far • Comparison of fraction of binaries in proto-stars and PMS stars constrain theories • Dependence upon environment (isolated vs cluster) is critical  surveys of different regions required S.Guilloteau – ISM & Star Formation

  9. Tidal Truncation • It does exist (e.g. GG Tau, Guilloteau, Dutrey & Simon) S.Guilloteau – ISM & Star Formation

  10. Tidal Truncations • But not always: AS 205 • ALMA can study significant samples rather than a few objects S.Guilloteau – ISM & Star Formation

  11. Disk around young stars • Current arrays have done about 20 sources... (e.g. IRAM PdB Survey) • ALMA sensitivity 50 times better ... • ALMA could do hundreds of sources in continuum, to a much better level, and at much higher angular resolution S.Guilloteau – ISM & Star Formation

  12. Zooming on inner disks • Nice, circularly symmetric, Keplerian disks don’t really exists • E.g. AB Aur 1.3 mm image at 0.6” resolution: “spiral” density enhancements 100 AU from the star (black: IR from Fukagawa et al 2004, White: mm from Piétu et al 2004) • Are such phenomena comon? Long-lived ? S.Guilloteau – ISM & Star Formation

  13. Stellar Masses (and more) • From the (Keplerian) rotation curve, measured from CO (Simon et al 2000) • Temperature from CO isotopes (Dartois et al 2003) • A sample of 40 sources, in CO and its isotopes at 0.2” resolution requires 2600 hours of ALMA ! S.Guilloteau – ISM & Star Formation

  14. Transition Disks ? • ALMA can image the “débris” disks around (young) stars • But also perhaps unveil the transition stage between proto-planetary disks and “débris” disks • Small disks just being found: e.g. BP Tau (Dutrey et al 2003) • But studies will require long integration time even with ALMA (>> 10 hours / object) S.Guilloteau – ISM & Star Formation

  15. Long term schedule • Proper motions can be measured with ALMA • Clumps in “debris” disks ( evidence for planets ?) • Orbital motions of proto-stellar condensations in massive star forming regions • Plan in advance and for the long term... S.Guilloteau – ISM & Star Formation

  16. Chemistry • Chemistry is a major issue in all components of the ISM • ALMA will be invaluable in many areas, due to high sensitivity, angular resolution and frequency coverage (especially sub-mm domain) • Examples • Diffuse ISM in absorption against quasars (e.g. Lucas & Liszt) • Shock chemistry in outflows • Chemistry in proto-stellar envelopes • Chemistry in proto-stellar disks • Hot core chemistry • PDR regions S.Guilloteau – ISM & Star Formation

  17. Diffuse Clouds • e.g. Sulfur chemistry (Lucas & Liszt 2003) • ALMA can reach much fainter sources • ALMA can reach much weaker lines (isotopes...) S.Guilloteau – ISM & Star Formation

  18. Outflows • High angular resolution required to resolve multiple shocks in outflow system (L1157, Bachiller & Perez-Guttierez 1997) S.Guilloteau – ISM & Star Formation

  19. Hot Cores • Angular resolution is essential to separate multiple cores • E.g. W3(OH) (Wyrowski et al 1997) S.Guilloteau – ISM & Star Formation

  20. Proto-Stellar envelopes • Short spacing information is essential (i.e. ACA and total power) • E.g. N2H+ in IRAM 04191 (Belloche et al 2002) S.Guilloteau – ISM & Star Formation

  21. Photo Dissociation Regions • e.g. Orion Bar (Lis & Schilke 2003) (False color: CO(7-6) Black contours: H2 v = 1 0 S(1) Red contours: O I 1.32 μm Blue contours: H13CN(1-0) White contours: 13CO(3-2) ) • Sub-mm data (for high excitation lines) and short-spacing information essential S.Guilloteau – ISM & Star Formation

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