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L 4: Collapse phase – observational evidence

L 4: Collapse phase – observational evidence. Background image: courtesy Gålfalk & Liseau, Serpens Core with VLT ANTU and ISAAC. L 4: Collapse phase – observational evidence. What is the problem ?. How to solve it ?. Known Methods & Techniques. L 4: Collapse phase – observational evidence.

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L 4: Collapse phase – observational evidence

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  1. L 4: Collapse phase – observational evidence Background image: courtesy Gålfalk & Liseau, Serpens Core with VLT ANTU and ISAAC L 4 - Stellar Evolution II: August-September, 2004

  2. L 4: Collapse phase – observational evidence What is the problem ? How to solve it ? Known Methods & Techniques L 4 - Stellar Evolution II: August-September, 2004

  3. L 4: Collapse phase – observational evidence What is the problem ? Theories may give different answers what to look for – but predictions include L 4 - Stellar Evolution II: August-September, 2004

  4. L 4: Collapse phase – observational evidence How to solve it ? or - how and where to look ? In dense interstellar clouds with infrared techniques ! L 4 - Stellar Evolution II: August-September, 2004

  5. Protostars are the Holy Grail of infrared astronomy Any observational difficulties ? L 4 - Stellar Evolution II: August-September, 2004

  6. L 4: Collapse phase – observational evidence (Known) Methods & Techniques Radiation (1) Continuum (2) Spectral Lines L 4 - Stellar Evolution II: August-September, 2004

  7. Continuum (Proto-)stellar photospheres Free-free gas emission Thermal radiation from (radiatively) heated dust grains Thermal radiation from (radiatively) heated dust grains To infer the total mass one needs Gas-Dust Relation [ generally assumed: m(g)/m(d) = 100 ] L 4 - Stellar Evolution II: August-September, 2004

  8. notice the spatial scales & time scales • Continuum Observations and Theoretical Models Spectral Energy Distributions SEDs Current Paradigm Astronomical Taxonomy Adapted from van Zadelhoff 2002, PhD thesis L 4 - Stellar Evolution II: August-September, 2004

  9. Continuum Observations + Spectral Energy Distributions (SEDs) SED fitting Theoretical models protostar Adams, Lada & Shu 1987ApJ 312, 788 L 4 - Stellar Evolution II: August-September, 2004

  10. Continuum Observations + Spatial Profile fitting Theoretical models IRS 5 L1551 KAO 50 mm I / Ipeak 100 mm residuals radial offset ( ´´ ) Butner et al. 1991 ApJ 376, 636 L 4 - Stellar Evolution II: August-September, 2004

  11. FIR & submm SCUBA 850 mm 450 mm • Continuum Spatial Profile fitting Observations Azimuthal Intensity Distribution Shirley et al. 2000 ApJS 131, 249 L 4 - Stellar Evolution II: August-September, 2004

  12. Compare to theory of collapse (see L 3) centrally condensed Bonnor 1956 MNRAS 116, 351 flat distribution Shu 1977 extreme case L 4 - Stellar Evolution II: August-September, 2004

  13. See also L 1: Motte et al. made fits at 1.3 mm => mostly Bonnor-Ebert spheres (flat) and r Oph A with I(r) ~ r - 2 and furthermore obtained ... L 4 - Stellar Evolution II: August-September, 2004

  14. Also Johnstone et al. 2000, ApJ 545, 327 Motte et al. 1998, AA 336, 150 Clump Mass Spectrum & IMF 1 clump - 1 star no further Fragmentation ? - see Eduardo (L 3) L 4 - Stellar Evolution II: August-September, 2004

  15. Continuum B 335 FIRS Spatial Profile fitting Firstly and only directly observed r ~ r - 1.5 profile Keck-I, K band (Hodapp 1998, ApJ 500, L 183) L 4 - Stellar Evolution II: August-September, 2004

  16. IRAM-PdB Interferometer 1.2 mm 3 mm Infall ? ``YES´´ Inside-out ? ``NO´´ Harvey et al. 2003, ApJ 583, 809 L 4 - Stellar Evolution II: August-September, 2004

  17. Continuum Observations Theoretical models Major pitfalls/caveats: Geometry - spheres vs disks Calorimetric vs `true´ Luminosities Dust Optical Depths (Properties) Temperatures (Dust and Gas) Inhouse work, see, e.g. : Larsson et al. 2000 White et al. 2000, AA L 4 - Stellar Evolution II: August-September, 2004

  18. (2)Spectral Lines What lines – species ? Physical Conditions of Excitation Cold ( Tk ~ a few x 10 K ~ meV ) Large AV (no / little external radiation) and dense (n > 103 cm -3): collisional excitations dominate level populations ( if t << 1 ) (low-lying) Rotational Transitions in Molecules mostly neutrals but CosmicRays => molecular ions and e- L 4 - Stellar Evolution II: August-September, 2004

  19. (2) Spectral Lines • Optically thin lines • Optically thick lines does not necessarily imply there’s `nothing´ there Why ? L 4 - Stellar Evolution II: August-September, 2004

  20. (2) Spectral Lines Theoretical profiles: cf. L3 Symmetrical Profiles • Optically thin lines • Optically thick lines (a?) no, spatial resolution Ammonia NH3 (b?) Foster & Chevalier 1993, ApJ 416, 303 L 4 - Stellar Evolution II: August-September, 2004

  21. Theoretical profiles (2) Spectral Lines Asymmetrical Profiles • Optically thin lines • Optically thick lines cloud center Carbon monoxide CO =12C16O (a?) and Isotopes (b?) offset ...hmm..., needs to be verified Leung & Brown 1977, ApJ 214, L73 L 4 - Stellar Evolution II: August-September, 2004

  22. (2) Spectral Lines Theoretical profiles warmer: more intensity Asymmetrical Profiles cooler: less intensity (b) Optically thick lines los for negative temperature gradient Shu Infall Zhou et al. 1993, ApJ 404, 232 L 4 - Stellar Evolution II: August-September, 2004

  23. inside-out collapse (Shu 1977, ApJ 214, 488) (see: L 3) B 335 p = -1.5 a = -0.5 p = -2 a = 0 not from Shu model Rinf = cstinf adapted from Hartstein & Liseau 1998, AA 332, 703 L 4 - Stellar Evolution II: August-September, 2004

  24. Theoretical profiles (2) Spectral Lines + Observations (b) Optically thick lines high bluelow red Asymmetrical Profiles Carbon Sulfide CS Hartstein & Liseau 1998, AA 332, 703 L 4 - Stellar Evolution II: August-September, 2004

  25. Observed & Theoretical profiles (2) Spectral Lines 13CO C18O (b) Optically thick lines (non-)equilibrium and information content thermalised Example: Carbon Monoxide 13CO Carbon Sulfide CS Hartstein & Liseau 1998, AA 332, 703 L 4 - Stellar Evolution II: August-September, 2004

  26. (2) Spectral Lines B 335 infall model oH2O (1-0) 10´´ 20´´ 120´´ (b) Optically thick lines Observation: dependence of profiles on spatial resolution (``beam´´) 24´´ 38´´ 51´´ CS (2-1) Carbon Sulfide CS Water Vapour H2O L 4 - Stellar Evolution II: August-September, 2004

  27. Observed + Theoretical Profiles Single Dish B 335 Interferometer Observation: no wings Inside – out collapse: wings Wilner et al. 2000, ApJ 544, L69 L 4 - Stellar Evolution II: August-September, 2004

  28. (3) Continuum and Spectral Lines Theoretical profiles + Observations e.g. Stark et al. 2004, ApJ 608, 341 Inhouse, e.g.: Larsson et al. – Odin H2O + ground based Schöier et al. – ground based inc. chemistry r Oph A IRAS 16293 ( r Oph east ) ... but steady state models .... of a highly dynamic situation... L 4 - Stellar Evolution II: August-September, 2004

  29. Outflow contamination & confusion! Current Paradigm - ? `` finn fem fel ´´ Adapted from van Zadelhoff 2002, PhD thesis L 4 - Stellar Evolution II: August-September, 2004

  30. ISO SWS & LWS + submm/mm FOV = 2.5 X 2.5 amin2 (0.2 X 0.2 pc2) Fitting the observed SED*: Menv = 6 Mo L = 140 Lo * 2-D radiative transfer (Larsson et al. 2002, AA 386, 1055) Serp SMM 1 (S68 FIRS 1)* Infall Candidate Outflow Source Disk Source * D = 310 pc L 4 - Stellar Evolution II: August-September, 2004

  31. Modeling the Line Emission Emission not from Disk Infalling Envelope but Outflow/Shocks L 4 - Stellar Evolution II: August-September, 2004

  32. Outflow contamination & confusion! Single Stars? Current Paradigm - ? `` finn fem fel ´´ Adapted from van Zadelhoff 2002, PhD thesis L 4 - Stellar Evolution II: August-September, 2004

  33. Number of Infall Candidates: Reasonable ? Expected ? * Object Classes and Lifetimes SFR of the solar neighbourhood Consistent picture? Magnus´ IMF talk *High mass starformation – cloud/cluster collapse L 4 - Stellar Evolution II: August-September, 2004

  34. L 4: conclusions • a variety of observational techniques are exploited • a number of collapse candidates have been found • all are strong outflow sources • multiplicity is common • L 4: open questions • How many collapse processes do occur in nature ? • more than one ? which ? • What is the `certain´ collapse tracer ? • What spectral & spatial resolution is needed ? • Are stars/BDs/planets formed differently ? How ? L 4 - Stellar Evolution II: August-September, 2004

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