Observing Star-Formation From the Interstellar Medium to Star-Forming Cores On-Line Version, 1999Observing Star Formation From the ISM to Star-Forming CoresHistory: Theory and Optical ObservationsSlide 4Important Distinction to Keep in MindSpectral-Line Mapping Adds Velocity DimensionOrion: 13CO Channel MapsMolecular OutflowsJeans Mass, Virial Mass, and Filling Factors in the ISMWhat do we need to explain?Self-similar Structure on Scales from 100 pc to 0.1 pc...in Orion“Clump” Mass Distribution“Larson’s Law” Scaling Relations (1981)Slide 14Rough Virial Equilibrium in Star-forming regionsDensity-Velocity-Magnetic Field StructureVelocity StructureVelocity Coherent Cores* Where does the self-similarity end?Slide 19Similar “Transition” Found in Spatial Distribution of StarsSlide 21Magnetic Field StructureUsing Polarization to Map Magnetic FieldsUsing Polarimetry to Map Field StructureSlide 25Magnetic Field Structure: Emission PolarimetryCloud LifetimesThe Effects of a Previous Generation of StarsSlide 29Initial Conditions for Star-Formation (Version 99)Slide 31Thanks to:What now?The PleiadesBright Nebula: OrionDark Nebula: The HorseheadThe Electromagnetic SpectrumA Dense Core: L1489A Dark Cloud: IC 5146Observing Star-FormationObserving Star-FormationFrom the Interstellar MediumFrom the Interstellar Mediumto Star-Forming Coresto Star-Forming CoresOn-Line Version, 1999On-Line Version, 1999Alyssa A. GoodmanHarvard UniversityDepartment of Astronomyhttp://cfa-www.harvard.edu/~agoodmanObserving Star Formation Observing Star Formation From the ISM to Star-Forming CoresFrom the ISM to Star-Forming CoresHistoryHistoryThe Optical and Theoretical ISM-A Quick TourA Quick TourThe multi-wavelength ISMWhat do we need to explain?What do we need to explain?Density/Velocity/Magnetic Field Structure+Initial Conditions for Star-FormationInitial Conditions for Star-FormationHistory: Theory and Optical History: Theory and Optical ObservationsObservationsTheories of Cosmology + Stellar Evolution (c. 1925+)•Stellar Population Continuously Replenished•Bright Blue Stars Very YoungStars Illuminating Reflection Stars Illuminating Reflection Nebulae Should Be YoungNebulae Should Be YoungOptical Observations (c. 1900+)•Bright Nebulae Often Associated with Dark Nebulae-Perhaps Dark Nebulae are Sites of Perhaps Dark Nebulae are Sites of Star-Formation?Star-Formation?...Theories of Star-formation prior to ~1970Jeans InstabilityGalaxy"Velocity Coherent" Dense CoreYoung Stellar Object +OutflowStarstimeSelf-Similar, Turbulent, "Larson's Law" CloudsA Quick Tour A Quick Tour (based on (based on optical, near-IR, optical, near-IR, far-IR, sub-mm, mm- far-IR, sub-mm, mm- and cm-waveand cm-wave observations) observations)(a.k.a. GMC or Cloud Complex)Important Distinction to Keep in Important Distinction to Keep in MindMindMost theories apply to formation of Low-Mass Stars (e.g. the Sun)Shu et al. inside-out collapse modelFormation of Massive (e.g. O & B) Stars may be physically different than low-mass caseIs triggering required?Elmegreen & Lada proposal--effects of nearby stars?Ionization differences?Spectral-Line Mapping Adds Velocity DimensionBut remember...Scalo's “Mr. Magoo” effectMountains do not move (much). Interstellar clouds do.Spectral Line ObservationsLine-profile FittingorChannel MapsorIntegrated Intensity MapsContour MaporSimilar "2-D" Displayof 3-D informationMountain RangeOrion:Orion:1313CO CO ChannelChannelMapsMapsBally 1987Bally 19878877663 km s3 km s-1-15544Molecular OutflowsFCRAOBIMAFCRAO+BIMARedshifted CO emission (Zhang et al. 1996)Blueshifted CO emission (Zhang et al. 1995)NH Half-Power Contour (Bachiller et al. 1993)3L11570.1 pcJeans Mass, Virial Mass, Jeans Mass, Virial Mass, and Filling Factors in the and Filling Factors in the ISMISMType of Region DensityFWHMLinewidthTFWHMThermalLinewidthSizeJeansLengthJeansMassVirialMassSphericalMassJeansMasses inSphereImplied"FillingFactor"[ptcl/cc] [km/s] [K] [km/s ] [pc] [pc] [Msuns][Msuns] [Msuns] [number of][Mvir/Msphere]H I Cloud 5 9 100 1.95 400 58.2 29177 3.4E+06 4.1E+06 1.4E+02 82%Giant Molecular Cloud 50 7 30 0.77 200 5.2 402 1.0E+06 5.2E+06 1.3E+04 20%Dark Cloud 3000 2 15 0.54 5 0.5 18 2.1E+03 4.8E+03 2.6E+02 43%Dense Core 25000 0.5 10 0.44 0.2 0.1 3 5 3 ~1 ~100%Jeans Mass>>Typical Stellar Masses for all but Dense CoresFilling Factor Low for Molecular Clouds other than Dense CoresWhat do we need to What do we need to explain?explain?Self-similar Structure Self-similar Structure on Scales from 0.1 to 100 pc“Clump” Mass Distribution Mass Distribution & Relation to IMFRough Virial Equilibrium Virial Equilibrium in Star-forming regionsOrigin of “Larson’s Law” “Larson’s Law” Scaling RelationsDensity-Velocity-Magnetic Field StructureCloud LifetimesLifetimesSelf-similar Structure on Scales from 100 pc to 0.1 pc...in Orion65 pc3.5 pc0.6 pc0.6 pcMaddalena et al. 1986CO Map, 8.7 arcmin resolutionDutrey et al. 1991C18O Map, 1.7 arcmin resolutionWiseman 1995Wiseman 1995NHNH33 Map, 8 arcsec resolution Map, 8 arcsec resolutionColumbia-Harvard “Mini”AT&T Bell-Labs 7-mVLAVLA“Clump” Mass DistributionΩWhat is a clump?Structure-FindingAlgorithmsE. Lada 1992+=dense coreCS (21)Typical Stellar IMFdN dM  M 1.6What does the clump “IMF” look like?E. Lada et al. 1991vyx•CLUMPFIND (Williams et al. 1994)•Autocorrelations (e.g. Miesch & Bally 1994)•Structure Trees (Houlahan & Scalo 1990,92)•GAUSSCLUMPS (Stutzki & Güesten 1990)•Wavelets (e.g. Langer et al. 1993)•Complexity (Wiseman & Adams 1994)•IR Star-Counting (C. Lada et al. 1994)Salpeter 1955Miller & Scalo 1979dN dM  M 2.50.3““Larson’s Law” Larson’s Law” Scaling RelationsScaling Relations (1981)(1981)(line width)~(size)1/2(density)~(size)-1Curves assume M=K=G (Myers & Goodman 1988)GM5R2T2NT2NT223B28nmavgvA23T2kTmavgVirial Equilibrium and Larson’s LawsVirial Theorem (G=K)Non-thermal=Magnetic (K=M)(Myers & Goodman 1988)Sound speedIf T2NT2, then Larson’s Laws (Larson 1981)~R0.5n~R 1so that virial equilibrium + either of Larson’s Laws gives other.n154mavgGR----2Rough Virial Equilibrium in Star-forming regionsM=K=GRough Equipartition in ~all of Cold ISMM=KLimiting Speed in Cold ISM is Limiting Speed in Cold ISM is Alfvén Speed, not Sound Alfvén Speed, not Sound Speed ... vSpeed ...