Observing Star Formation From the Interstellar Medium to Star Forming Cores On Line Version 1999 Alyssa A Goodman Harvard University Department of Astronomy http cfa www harvard edu agoodman Observing Star Formation From the ISM to Star Forming Cores History The Optical and Theoretical ISM A Quick Tour The multi wavelength ISM What do we need to explain Density Velocity Magnetic Field Structure Initial Conditions for Star Formation History Theory and Optical Observations Theories of Cosmology Stellar Evolution c 1925 Stellar Population Continuously Replenished Bright Blue Stars Very Young Stars Illuminating Reflection Nebulae Should Be Young Optical Observations c 1900 Bright Nebulae Often Associated with Dark Nebulae A Quick Tour Stars e based on optical near IR far IR sub mm mmand cm wave observations tim Galaxy Young Stellar Object Outflow Velocity Coherent Dense Core Self Similar Turbulent Larson s Law Clouds a k a GMC or Cloud Complex Important Distinction to Keep in Mind 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 Dimension Spectral Line Observations But remember Line profile Fitting or Channel Maps or Integrated Intensity Maps Mountain Range Contour Map or Similar 2 D Display of 3 D information Scalo s Mr Magoo effect Mountains do not move much Interstellar clouds do Orion 13 CO Channel Maps 3 km s 1 4 5 6 7 8 Bally 1987 Molecular Outflows L1157 FCRAO BIMA FCRAO BIMA 0 1 pc Redshifted CO emission et al 1996 Zhang Blueshifted CO emission et al 1995 Zhang NH et al Bachiller 1993 3 Half Power Contour Jeans Mass Virial Mass and Filling Factors in the ISM Type of Region FWHM Jeans Implied FWHM Thermal Jeans Jeans Virial SphericalMasses in Filling DensityLinewidth T LinewidthSize Length Mass Mass Mass Sphere Factor ptcl cc km s K km s pc pc Ms uns Ms uns Ms uns number of Mvir Ms phere H I Cloud 5 Giant Molecular Cloud 50 Dark Cloud 3000 Dense Core 25000 9 7 2 0 5 100 30 15 10 1 95 400 0 77 200 0 54 5 0 44 0 2 58 2 29177 3 4E 06 4 1E 06 5 2 402 1 0E 06 5 2E 06 0 5 18 2 1E 03 4 8E 03 0 1 3 5 3 1 4E 02 1 3E 04 2 6E 02 1 Jeans Mass Typical Stellar Masses for all but Dense Cores Filling Factor Low for Molecular Clouds other than Dense Cores 82 20 43 100 What do we need to explain Self similar Structure on Scales from 0 1 to 100 pc Clump Mass Distribution Relation to IMF Rough Virial Equilibrium in Star forming regions Origin of Larson s Law Scaling Relations Density Velocity Magnetic Field Structure Cloud Lifetimes Self similar Structure on Scales from 100 pc to 0 1 pc in Orion 65 pc 3 5 pc Maddalena et al 1986 Dutrey et al 1991 CO Map 8 7 arcmin resolution C18O Map 1 7 arcmin resolution Columbia Harvard Mini AT T Bell Labs 7 m 0 6 pc Wiseman 1995 NH3 Map 8 arcsec resolution VLA Clump Mass Distribution What is a clump Typical Stellar IMF Structure Finding Algorithms dN dM M 2 5 0 3 dense core Salpeter 1955 Miller Scalo 1979 What does the clump IMF look like y dN dM M 1 6 v x CS 2 1 E Lada 1992 E Lada et al 1991 CLUMPFIND Williams et al 1994 Autocorrelations e g Miesch Bally 1994 Structure Trees Houlahan Scalo 1990 92 GAUSSCLUMPS Stutzki G esten 1990 Wavelets e g Langer et al 1993 Complexity Wiseman Adams 1994 IR Star Counting C Lada et al 1994 Larson s Law Scaling Relations 1981 line width size 1 2 density size 1 Curves assume M K G Myers Goodman 1988 Virial Equilibrium and Larson s Laws R0 5 Larson s Laws n R 1 Larson 1981 GM 2 T 2 NT2 5R 2 2 B vA2 2 NT 3 3 8 nmavg T 2 NT2 Non thermal Magnetic K M Myers Goodman 1988 Sound speed T 2 kT m avg If Virial Theorem G K then 15 2 n 4 mavgG R so that virial equilibrium either of Larson s Laws gives other Rough Virial Equilibrium in Star forming regions M K G Rough Equipartition in all of Cold ISM M K Limiting Speed in Cold ISM is Alfv n Speed not Sound Speed vA vS Uniform and or Non Uniform Magnetic Support Turbulent and or Wavelike Magnetic Support Density Velocity Magnetic Field Structure Density Structure appearance of ISM algorithms self similarity Velocity Structure self similarity rotation coherence Magnetic Field Structure Zeeman Observations polarimetry uniformity non uniformity a k a Larson s Laws Velocity Structure Velocity Coherent Dense Cores low mass dense cores end of self similar cascade Rotation detectable but not very supportive Velocity Coherent Cores Where does the self similarity end for T K 10 K 9 8 6 5 4 L1251A C 3 18 O 1 0 Binned FC RAO Data v TA 0 4 0 1 2 2 3 4 5 6 7 8 9 2 1 Antenna Temperature T A Non Thermal Line Width km s for T K 10 K 1 7 Non Thermal Line Width km s Line Width The Transition from Self Similarity to Velocity Coherence K L1251A NH 1 9 3 J K 1 1 Binned Haystack Data 8 v TA 7 0 05 0 05 Break in slope at 0 1 pc 6 5 4 3 2 5 6 7 8 9 0 1 2 3 5 Antenna Temperature TA K Radius Goodman Barranco Heyer Wilner 1995 96 low mass 4 6 7 8 9 What is Velocity Coherence narrower FWHM core FWHM wider FWHM Velocity Coherent Core Chaff Cumulatively Obeys Larson s Laws Similar Transition Found in Spatial Distribution of Stars Surface Density of Stellar Companions as a Function of Angular Separation in Taurus Auriga Velocity Coherent Regime break in slope at 0 04 pc Larson 1995 Turbulent Regime Large scales 0 1 pc characterized by cloud mass distribution fractal turbulent Small scales 0 1 pc characterized by fragmentation of cores Jeans instability Is Rotation Important 1 2 0 44 1 1 0 L1251E 0 8 0 20 0 6 clouds rotationally stabilized against L1082A 0 4 fragmentation no binaries due to fission G ra d ie n t R k m s B35A 0 2 no binaries due to fragmentation 0 0 0 4 0 5 Goodman et al 1993 0 6 0 7 0 8 1 v km s 0 9 1 0 1 1 Rotation Detectable in Dense Cores Important in Fragmentation but not in support 0 02 Magnetic Field Structure Large scale field in Spiral Galaxies follows arms mostly in plane Polarization of Background Starlight not all grains are created equal not useful for cold dense regions Polarization of Emitted Grain Radiation potentially useful for dense regions Field Uniformity Non Uniformity Using …