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

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.”

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-)

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

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

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).

~10 7 yr Ambipolar Diffusion Shu et al.; Mouschovias et al. “Squeezed” Ambipolar Diffusion/ Turbulent Fragmentation leading to A.D. Li & Nakamura Padoan et al. Unmagnetized Turbulent Fragmentation MacLow & Klessen Turbulent Fragmentation + Competitive/Bondi-Hoyle Accretion Bate et al.; Padoan et al. ~10 5 yr Free Fall Time (Newton) See also Ballesteros-Paredes, Vazquez-Semadeni et al.; Ostriker, Stone & Gammie; Klein, McKee, Krumholz et al. ; Tilley & Pudritz; Hartmann & Burkert & more Role of Interactions Role of a “Core” ISM to IMF

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

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

~10 7 yr Ambipolar Diffusion Turbulent Fragmentation leading to A.D. Turbulent Fragmentation + Competitive/Bondi-Hoyle Accretion ~10 5 yr Free Fall Time Role of Interactions Role of a “Core” ISM to IMF

How Should this Picture Look?

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

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

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

Goodman & Arce 2004 PV Ceph: Speeding at 22 km/s

Dust Emission Map Goodman & Arce 2004 Optical Image of NGC 7023 Tom Licha, 2002 PV Ceph PV Ceph: Speeding at 22 km/s “Exit wound” NGC pc in 500,000 yr km/s)

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

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

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

Substituting Spatial Statistics for Temporal Sampling

Distribution of Stars Current Positions EasiestIR-radio surveys (e.g. Spitzer c2d, GLIMPSE) MassesPretty hard (IR) luminosity-mass relations AgesVery hardIR spectroscopy of PMS stars (models??) Outflow properties VelocitiesVery, very hard Proper motion: needs future technology in most cases Radial Velocity: nearing feasibility with IR spectroscopy

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

Distribution of Gas & Dust Column Density Easiest, but… NIR or MIR extinction mapping is best (see COMPLETE) MassesPretty hard Describing 3D geometry a problem & emission-to-mass conversion is uncertain (gas & dust chemistry) Time Evolution Very hard Even with velocities from molecular lines, gravitational binding energy uncertain 3D velocity field Very, very hard Proper motion: impossible w/o masers Radial Velocity: easy, but hard to define “features”

Near-Infrared Optical

The Value of Coordinated Observations: B68 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 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

Perseus Ophiuchus Serpens

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) COMPLETE The COordinated Molecular Probe Line Extinction Thermal Emission Survey

Perseus Thermal Dust Emission + Spectral Lines (~100, CO Spectra)

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

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

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)

L1688 class II Class I sources are clustered peak surface density is a few x 10 2 /pc 2 Slide courtesy of Lori Allen (c2d + IRAC GTO data)

L1688 class II C 18 O integrated intensity Class I sources are primarily concentrated along molecular gas ridge C 18 O map courtesy D. Li Slide courtesy of Lori Allen (c2d + IRAC GTO data)

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.”

Emission, Absorption, Emission

“Equipartition” Models Summary Results from SCF Analysis Falloff of Correlation with Scale Magnitude of Spectral Correlation at 1 pc Padoan, Goodman & Juvela 2003 “Reality” Scaled “Superalfvenic” Models “Stochastic” Models

Do existing turbulence simulations “match” molecular clouds? 13 CO maps Super-Alfvénic MHD Simulations Falloff of Spectral Correlation with Scale Magnitude of Spectral Correlation at 1 pc Padoan, Goodman & Juvela 2003