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Mapping the Interstellar Medium Alyssa A. Goodman Harvard-Smithsonian Center for Astrophysics (on sabbatical 2001-2 at Yale University) cfa-www.harvard.edu/~agoodman
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Barnard’s Interstellar Medium
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“Barnard’s Method”: Star Counting Observations by Alves, Lada & Lada 1999 uCounts of stars per unit area measure how much material must be producing obscuration.
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Barnard’s Interstellar Medium
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The “Modern” Interstellar Medium
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Telescopes Used in Our Mapping of the ISM NTT, VLT (Chile) FCRAO & CfA (Mass.) JCMT (Hawaii) IRAM 30-m (Spain) ATCA+Parkes (Australia) KPNO 12-m & HHT (Arizona) HST, IRAS (Earth Orbit) SIRTF (Sun Orbit) Arecibo (Puerto Rico) Nagoya 4-m (Japan)
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The “Modern” ISM IRAS Satellite Observation, 1983 Barnard’s Optical Photograph of Ophiuchus Remember: Cold (10K) dust glows, like a blackbody, in the far-infrared.
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Tutorial: Absorption, Scattering, Emission & Extinction Emitter Absorber “Emission” Note: Absorption + Scattering = “Extinction” “Scattering” “Absorption” Scatterer
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Multiwavelength Milky Way
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Advanced Tutorial: “Wavelength Dependence of Extinction” “Dust Grain” “Dust Grain” Light is “Extinguished” & Does not Reach Us Light Goes Right by & Reaches Us
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Bok Globule (Core)
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Seeing “through” the Clouds Near-Infrared Optical
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Multiwavelength Milky Way
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Star Formation (a.k.a. GMC or Cloud Complex)
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Thermal Dust Emission in the Orion Star- Forming Region
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Outflows Magnetohydrodynamic Waves Thermal Motions MHD Turbulence Inward Motions SNe/GRB H II Regions Star Formation in the ISM
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The “Modern” ISM IRAS Satellite Observation, 1983 Barnard’s Optical Photograph of Ophiuchus Remember: Cold (10K) dust glows, like a blackbody, in the far-infrared.
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The Very Cold ISM: 850 m Emission (T~15K) Motte, André & Neri 1998
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The “Modern” ISM M. Pound 1998 Contours show Molecular Line (CO) Map
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Galactic Longitude Velocity What NASA Didn’t Explain…but I will… “Molecular Hydrogen” (is really a CO map) Spectral Lines Give VELOCITY Galactic Longitude Galactic Latitude
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Molecular Clouds: The Stuff of New Stars Red Plate, Digitized Palomar Observatory Sky Survey The Oschin telescope, 48-inch aperture wide-field Schmidt camera at Palomar
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Radio Spectral-line Observations of Interstellar Clouds
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Tutorial: Velocity from Spectroscopy 1.5 1.0 0.5 0.0 -0.5 Intensity 400350300250200150100 "Velocity" Observed Spectrum All thanks to Doppler Telescope Spectrometer
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1.5 1.0 0.5 0.0 -0.5 Intensity 400350300250200150100 "Velocity" Observed Spectrum Telescope Spectrometer All thanks to Doppler Tutorial: Velocity from Spectroscopy
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Radio Spectral-line Observations of Interstellar Clouds
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Alves, Lada & Lada 1999 Radio Spectral-Line Survey Radio Spectral-line Observations of Interstellar Clouds
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Velocity as a "Fourth" Dimension No loss of information Loss of 1 dimension
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Giant Outflow from a Young Star (PV Ceph) Goodman & Arce 2002
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The NCP Loop in Atomic Hydrogen: Velocity Slices Data: Hartmann & Burton 1999; Figure: Ballesteros-Paredes, Vazquez-Semadeni & Goodman 2001
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Molecular or Dark Clouds "Cores" and Outflows Rotation, Outflow & Turbulence all rely on Velocity Measurements Jets and Disks Solar System Formation 1 pc = 3 lyr
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Molecular Spectral Line Mapping 2000 1990 1980 1970 1960 1950 Year 10 0 1 2 3 4 N channels, S/N in 1 hour, N pixels 10 2 3 4 5 6 7 8 (S/N)*N pixels *N channels N pixels S/N Product N channels That’s a one-thousand-fold “improvement” in 20 years.
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Real & Simulated Spectral Line Maps Based on work of Padoan, Nordlund, Juvela, et al. simulation shown used in Padoan & Goodman 2002.
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The Value of MHD Simulations Stone, Gammie & Ostriker 1999 Driven Turbulence; M K; no gravity Colors: log density Computational volume: 256 3 Dark blue lines: B-field Red : isosurface of passive contaminant after saturation =0.01 =1 T /10 K n H 2 /100 cm -3 B /1.4 G 2
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How Well do Numerical Models Match Reality? Power-Law Slope of SCF vs. Lag Magnitude of Spectral Correlation at 1 pc Padoan & Goodman 2002 “Reality” Scaled “Superalfvenic” Models “Stochastic” Models “Equipartition” Models
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Galactic Scale Heights from the SCF (v.2.0) Padoan, Kim, Goodman & Stavely-Smith 2001 HI map of the LMC from ATCA & Parkes Multi-Beam, courtesy Stavely-Smith, Kim, et al.
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Mapping Everything? (a.k.a. GMC or Cloud Complex)
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SIRTF’s 1st Plan for Star-Forming Regions The SIRTF Legacy Survey “From Molecular Cores to Planet-Forming Disks” Neal J. Evans, II, Principal Investigator (U. Texas) Lori E. Allen (CfA) Geoffrey A. Blake (Caltech) Paul M. Harvey (U. Texas) David W. Koerner (U. Pennsylvania) Lee G. Mundy (Maryland) Philip C. Myers (CfA) Deborah L. Padgett (SIRTF Science Center) Anneila I. Sargent (Caltech) Karl Stapelfeldt (JPL) Ewine F. van Dishoeck (Leiden)
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SIRTF Legacy Survey Perseus Molecular Cloud Complex (one of 5 similar regions to be fully mapped in far-IR by SIRTF Legacy)
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SIRTF Legacy Survey MIRAC Coverage 2 degrees ~ 10 pc
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Our Plan for the Future: COMPLETE The COordinated Molecular Probe Line Extinction Thermal Emission Survey Alyssa A. Goodman, Principal Investigator (CfA) João Alves (ESA, Germany) Héctor Arce (Caltech) Paola Caselli (Arcetri, Italy) James DiFrancesco (Berkeley) Doug Johnstone (HIA, Canada) Scott Schnee (CfA) Mario Tafalla (OAS, Spain) Tom Wilson (MPIfR/SMTO)
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Un(coordinated) Molecular-Probe Line, Extinction and Thermal Emission Observations Molecular Line Map Nagahama et al. 1998 13 CO (1-0) Survey Lombardi & Alves 2001Johnstone et al. 2001
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The Value of Coordination C 18 O Dust Emission Optical Image NICER Extinction Map Radial Density Profile, with Critical Bonnor-Ebert Sphere Fit Coordinated Molecular-Probe Line, Extinction & Thermal Emission Observations of Barnard 68 This figure highlights the work of Senior Collaborator João Alves and his collaborators. The top left panel shows a deep VLT image (Alves, Lada & Lada 2001). The middle top panel shows the 850 m continuum emission (Visser, Richer & Chandler 2001) from the dust causing the extinction seen optically. The top right panel highlights the extreme depletion seen at high extinctions in C 18 O emission (Lada et al. 2001). The inset on the bottom right panel shows the extinction map derived from applying the NICER method applied to NTT near-infrared observations of the most extinguished portion of B68. The graph in the bottom right panel shows the incredible radial-density profile derived from the NICER extinction map (Alves, Lada & Lada 2001). Notice that the fit to this profile shows the inner portion of B68 to be essentially a perfect critical Bonner-Ebert sphere
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Is this Really Possible Now? 1 day for a 13 CO map then 1 minute for a 13 CO map now
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COMPLETE, Part 1 Observations: Mid- and Far-IR SIRTF Legacy Observations: dust temperature and column density maps ~5 degrees mapped with ~15" resolution (at 70 m) NICER/2MASS Extinction Mapping: dust column density maps, used as target list in HHT & FCRAO observations + reddening information ~5 degrees mapped with ~5' resolution HHT Observations: dust column density maps, finds all "cold" source ~20" resolution on all A V >2” FCRAO/SEQUOIA 13 CO and 13 CO Observations: gas temperature, density and velocity information ~40" resolution on all A V >1 Science: Combined Thermal Emission (SIRTF/HHT) data: dust spectral-energy distributions, giving emissivity, T dust and N dust Extinction/Thermal Emission inter-comparison: unprecedented constraints on dust properties and cloud distances, in addition to high-dynamic range N dust map Spectral-line/N dust Comparisons Systematic censes of inflow, outflow & turbulent motions will be enabled—for regions with independent constraints on their density. CO maps in conjunction with SIRTF point sources will comprise YSO outflow census 5 degrees (~tens of pc) SIRTF Legacy Coverage of Perseus
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COMPLETE, Part 2 Observations, using target list generated from Part 1: NICER/8-m/IR camera Observations: best density profiles for dust associated with "cores". ~10" resolution SCUBA Observations: density and temperature profiles for dust associated with "cores" ~10" resolution FCRAO+ IRAM N 2 H + Observations: gas temperature, density and velocity information for "cores” ~15" resolution Science: Multiplicity/fragmentation studies Detailed modeling of pressure structure on <0.3 pc scales Searches for the "loss" of turbulent energy (coherence) FCRAO N 2 H + map with CS spectra superimposed. (Lee, Myers & Tafalla 2001).
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Mapping the Interstellar Medium Alyssa A. Goodman Harvard-Smithsonian Center for Astrophysics (on sabbatical 2001-2 at Yale University) cfa-www.harvard.edu/~agoodman
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