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Spitzer’s Chapter on Star Formation

Spitzer’s Chapter on Star Formation. Alyssa A. Goodman Harvard-Smithsonian Center for Astrophysics. Physical Processes in the Interstellar Medium (Spitzer 1978) 13.3 Gravitational Condensation and Star Formation.

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Spitzer’s Chapter on Star Formation

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  1. Spitzer’s Chapter on Star Formation Alyssa A. Goodman Harvard-Smithsonian Center for Astrophysics

  2. Physical Processes in the Interstellar Medium (Spitzer 1978)13.3 Gravitational Condensation and Star Formation “The detailed analysis of star formation is a complex topic, as well as a somewhat uncertain one.”

  3. Since “Spitzer,” The Book large-scale molecular-line mapping(1980’s-now) IRAS (1983); HST(1990-now); Chandra (1999-now); ISO(1997-8) wide-field ground-based IR imaging (1990’s -now) interferometric & A.O. imaging (1980’s-now) sub-mm imaging (1990’s-now) realistic 3D numerical simulations (1990’s/soon-)

  4. Galaxy Molecular Cloud Complex Circumstellar Disk+Outflow Star Cluster Star-Forming “Globule” Star-Forming “Globule” Number of Stars of each Mass Extrasolar System Stellar Mass ISM to IMF ?

  5. (Realistic?)3D Numerical Simulations • MHD turbulence gives “t=0” conditions; Jeans mass=1 M • 50 M, 0.38 pc, navg=3 x 105 ptcls/cc • forms ~50 objects • T=10 K • SPH, no B or ,  • movie=1.4 free-fall times Bate, Bonnell & Bromm 2002

  6. Physical Processes in the Interstellar Medium (Spitzer 1978)Chapter 13: Gravitational Motion The very last paragraph of Spitzer’s book (end of 13.3) reads: We conclude that the reduction of magnetic field made possible by plasma drift (ambipolar diffusion) is unimportant during the free-fall time. If magnetic forces, combined perhaps with centrifugal forces, maintain a cloud or fragment in hydrostatic equilibrium, [ambipolar diffusion] can significantly reduce the magnetic flux, permitting gradual contraction and possibly the resumption of free fall when the flux has fallen to a sufficiently low value (Nakano, 1976).

  7. ISM to IMF Role of a “Core” Role of Interactions See also Ballesteros-Paredes, Vazquez-Semadeni et al.; Ostriker, Stone & Gammie; Klein, McKee, Krumholz et al. ; Tilley & Pudritz; Hartmann & Burkert & more

  8. …inside this? Can this happen… Cores form by Ambipolar Diffusion Shu, Adams & Lizano 1987

  9. Bondi-Hoyle Accretion, not (Purely) Disk Accretion? Padoan et al. 2004 (astro-ph, Nov. 8)

  10. ISM to IMF Role of a “Core” Role of Interactions

  11. How Should this Picture Look?

  12. Star Formation in Space & Time 100,000 years to escape a 0.1 pc dense core at 1 km s-1

  13. Star Formation in Space & Time 5 Myr to escape a (7 pc) dark cloud at the sound speed

  14. Star Formation in Space & Time 10 Myr to escape a whole GMC at 10 km s-1

  15. PV Ceph: Speedingat 22 km/s Goodman & Arce 2004

  16. Optical Image of NGC 7023 Dust Emission Map “Exit wound” NGC 7023 Tom Licha, 2002 PV Ceph PV Ceph: Speedingat 22 km/s 10 pc in 500,000 yr (@20 km/s) Goodman & Arce 2004

  17. Spitzer Infrared Image: A. Noriega-Crespo (SSC/Caltech) Spitzer’s Forté HH 46-47 flow poking out of a globule, optical (DSS)

  18. Image from Stanke, McCaughrean & Zinnecker, 1999 How Fast is the Source of HH46-47 Moving? CO flow: Chernin & Masson 1991 HST image: Heathcote et al. 1996

  19. Image from Stanke, McCaughrean & Zinnecker, 1999 How Fast is the Source of HH46-47 Moving? CO flow: Chernin & Masson 1991 HST image: Heathcote et al. 1996

  20. Substituting Spatial Statistics for Temporal Sampling

  21. Distribution of Stars

  22. Spitzer Colors Stellar “Age”from SpitzerClassesI<1 Myr (major disk)II1 to 10 Myr (some disk)IIIolder TTS (almost no disk) Class I Models Class II Regime Class III Allen et al. 2004; see also Whitney et al. 2003,4

  23. Distribution of Gas & Dust

  24. Optical Near-Infrared

  25. Optical Image C18O Dust Emission Radial Density Profile, with Critical Bonnor-Ebert Sphere Fit NICER Extinction Map The Value of Coordinated Observations: B68 Coordinated Molecular-Probe Line, Extinction & Thermal Emission Observations of Barnard 68 This figure highlights the work of 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 C18O 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

  26. Perseus Ophiuchus Serpens

  27. The COordinated Molecular Probe Line Extinction Thermal Emission Survey COMPLETE Alyssa A. Goodman, Principal Investigator (CfA) João Alves (ESO, Germany) Héctor Arce (AMNH) Paola Caselli (Arcetri, Italy) James DiFrancesco (HIA, Canada) Jonathan Foster (CfA, PhD Student) Mark Heyer (UMASS/FCRAO) Helen Kirk (HIA, Canada) Di Li (CfA) Doug Johnstone (HIA, Canada) Jaime Pineda (CfA, PhD student) Naomi Ridge (CfA) Scott Schnee (CfA, PhD student) Mario Tafalla (OAN, Spain) Tom Wilson (ESO, Germany)

  28. IRAS Ndust H W(13CO) 2MASS/NICER Extinction H- emission,WHAM/SHASSA Surveys (see Finkbeiner 2003)

  29. What is the True Distribution of Star-Forming Material in Molecular Clouds?Goodman, Ridge & Schnee 2005

  30. L1688 class II Class II Sources are widely distributed NB: require detections in all 4 IRAC bands Slide courtesy of Lori Allen (c2d + IRAC GTO data)

  31. L1688 class II Class I sources are clustered peak surface density is a few x 102/pc2 Slide courtesy of Lori Allen (c2d + IRAC GTO data)

  32. C18O integrated intensity Class I sources are primarily concentrated along molecular gas ridge L1688 class II Slide courtesy of Lori Allen (c2d + IRAC GTO data) C18O map courtesy D. Li

  33. Physical Processes in the Interstellar Medium(Spitzer 2004!)13.3 Gravitational Condensation and Star Formation “The detailed analysis of star formation is a complex topic, as well as a somewhat uncertain one. It is only since the advent of sensitive infrared telescopes that we can peer inside the dark dusty regions where stars form to see the youngest stars. By combining measures of the stellar spatial and age distributions with measures of the gas and dust temperature, density, and compositional distributions, stellar and gas velocities, and magnetic field topology, one can test statistically-oriented but predictive theories of the production of stars over time.”

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