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

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

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

L 4 - Stellar Evolution II: August-September, (1)Continuum (Proto-)stellar photospheres Free-free gas emission Thermal radiation from (radiatively) heated dust grains To infer the total mass one needs Gas-Dust Relation [ generally assumed: m(g)/m(d) = 100 ] Thermal radiation from (radiatively) heated dust grains

L 4 - Stellar Evolution II: August-September, (1)Continuum Spectral Energy Distributions SEDs Observations and Theoretical Models Current Paradigm Adapted from van Zadelhoff 2002, PhD thesis Astronomical Taxonomy notice the spatial scales & time scales

L 4 - Stellar Evolution II: August-September, (1)Continuum Spectral Energy Distributions (SEDs) SED fitting Observations Theoretical models Adams, Lada & Shu 1987ApJ 312, protostar

L 4 - Stellar Evolution II: August-September, (1)Continuum Spatial Profile fitting Observations Theoretical models Butner et al ApJ 376, KAO 50  m 100  m IRS 5 L1551 residuals I / I peak radial offset ( ´´ )

L 4 - Stellar Evolution II: August-September, (1)Continuum Spatial Profile fitting Shirley et al ApJS 131, 249 FIR & submm SCUBA 850  m 450  m Observations Azimuthal Intensity Distribution

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

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

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

L 4 - Stellar Evolution II: August-September, (1)Continuum Spatial Profile fitting Firstly and only directly observed  ~ r profile Keck-I, K band (Hodapp 1998, ApJ 500, L 183) B 335 FIRS

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

L 4 - Stellar Evolution II: August-September, (1)Continuum Major pitfalls/caveats: Geometry - spheres vs disks Calorimetric vs `true´ Luminosities Dust Optical Depths (Properties) Temperatures (Dust and Gas) Observations Theoretical models Inhouse work, see, e.g. : Larsson et al White et al. 2000, AA

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

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

L 4 - Stellar Evolution II: August-September, (2) Spectral Lines (a)Optically thin lines (b)Optically thick lines Theoretical profiles: cf. L3 Foster & Chevalier 1993, ApJ 416, 303 Ammonia NH 3 (a?) (b?) Symmetrical Profiles no, spatial resolution

L 4 - Stellar Evolution II: August-September, (2) Spectral Lines (a)Optically thin lines (b)Optically thick lines Theoretical profiles Leung & Brown 1977, ApJ 214, L73 Carbon monoxide CO = 12 C 16 O (a?) and Isotopes (b?) Asymmetrical Profiles cloud center offset...hmm..., needs to be verified

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

L 4 - Stellar Evolution II: August-September, inside-out collapse (Shu 1977, ApJ 214, 488) (see: L 3) B 335 not from Shu model p = -1.5 p = -2 R inf = c s t inf  = -0.5  = 0 adapted from Hartstein & Liseau 1998, AA 332, 703

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

L 4 - Stellar Evolution II: August-September, (2) Spectral Lines (b) Optically thick lines Observed & Theoretical profiles Hartstein & Liseau 1998, AA 332, 703 Example: Carbon Monoxide 13 CO Carbon Sulfide CS (non-)equilibrium and information content thermalised C 18 O 13 CO

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

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

L 4 - Stellar Evolution II: August-September, (3) Continuum and Spectral Lines Theoretical profiles + Observations Inhouse, e.g.: Larsson et al. – Odin H 2 O + ground based Schöier et al. – ground based inc. chemistry  Oph A IRAS (  Oph east )... but steady state models.... of a highly dynamic situation... e.g. Stark et al. 2004, ApJ 608, 341

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

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

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

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

L 4 - Stellar Evolution II: August-September, 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, 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 ?