Star Formation Then and Now Alyssa A. Goodman Harvard-Smithsonian Center for Astrophysics (currently on sabbatical at Yale) cfa-

Star Formation Then and Now “We should not hire a star formation theorist. Star formation is too messy a problem, and will never be solved. It’s not worthy of a theorist.” —renowned astrophysicist at a top research university, 2002 The inspiration for this talk:

Star Formation Before Then Global Instability (e.g. Jeans) Fragments Cloud (hierarchically) time~10 6 years Hoyle 1953 Fragments Collapse Under Gravity into “Protostars” time~10 5 years

Star Formation Before Then A Group of Young “Zero-Age Main Sequence” Stars is Born

Since “Then” Does this look like a global Jeans instability to you?

All Between “Then” & “Now” Then≈1978 Now ≈2002 Discovery of bipolar molecular outflows from young stars. 1st all-sky surveys for embedded protostars (e.g. IRAS). Discovery of line width-size relations, and attribution to turbulence. Understanding that most stars form in clusters and groups (including binaries). Debate over clump mass function, and relation to IMF. First measurements of magnetic fields in molecular clouds. Discovery of “giant” (>1 pc) Herbig-Haro flows. 1st 3-D MHD simulations of molecular clouds. First observations of protostellar disks (radio, IR, optical). Discovery of extrasolar planets.

Outflows Magnetohydrodynamic Waves Thermal Motions MHD Turbulence Inward Motions SNe/GRB H II Regions Star Formation “Now”

Molecular or Dark Clouds "Cores" and Outflows An Heuristic View Jets and Disks Extrasolar System 1 pc

What I’d like to talk about today Molecular Spectral-Line Mapping Then & Now –Quick Tutorial –Examples 1.The Value of MHD Simulations, The Spectral Correlation Function Goal is to improve simulations enough so that they “match” observations empirically, then use the matching simulations to “experiment” with ISM conditions. 2.Outflows Then, Now, and Then, and Now… Episodicity, Energy Input, Moving Sources? How do outflows effect clouds in the long run?? Beyond Now: The COMPLETE Survey

Radio Spectral-line Observations of Interstellar Clouds BUT remember: Making this kind of map always loses 1 dimension.

Velocity as a "Fourth" Dimension No loss of information Loss of 1 dimension

Lee, Myers & Tafalla Spectral Line Maps Simulated map, based on work of Padoan, Nordlund, Juvela, et al. Excerpt from realization used in Padoan & Goodman 2002.

Molecular Spectral Line Mapping: Then to Now Year N channels, S/N in 1 hour, N pixels (S/N)*N pixels *N channels N pixels S/N Product N channels That’s a one-thousand-fold “improvement” in 20 years.

Not What I Want to Talk About Courtesy BIMA Image Gallery

MHD Simulations as an Interpretive Tool Stone, Gammie & Ostriker 1999 Driven Turbulence; M  K; no gravity Colors: log density Computational volume: 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

The Spectral Correlation Function (SCF) Figure from Falgarone et al Comparison Spectra Target Spectrum Measures Similarity of Comparison Spectra to Target

SCF, v.1.0 (Rosolowsky, Goodman, Wilner & Williams 1999) Figure from Falgarone et al etc.

Application of the SCF greyscale: T A =0.04 to 0. 3 K Antenna Temperature Map “Normalized” SCF Map Data shown: C 18 O map of Rosette, courtesy M. Heyer et al. Results: Padoan, Rosolowsky & Goodman greyscale: while=low correlation; black=high

Original Data Randomized Positions SCF Distributions Normalized C 18 O Data for Rosette Molecular Cloud

No gravity, No B fieldNo gravity, Yes B fieldYes gravity, Yes B field Simulations Insights from SCF v.1.0 Rosolowsky, Goodman, Williams & Wilner 1999 Self-Gravitating, Star-Forming Region Unbound High-Latitude Cloud Observations Lag & scaling adjustable Only lag adjustable Only scaling adjustable No adjustments

Preliminary SCF (v.1.0) Comparisons Mean SCF Value Change in Mean SCF with Randomization Increasing Similarity of Spectra to Neighbors G,O,S MHD +grav Falgarone et al pure HD. MacLow et al. MHD L134A 12 CO(2-1). L CO(2-1) Pol. 13 CO(1-0) L134A 13 CO(1-0) HCl2 C 18 O Peaks HCl2 C 18 O Rosette C 18 O Rosette C 18 O Peaks SNR H I Survey Rosette 13 CO Rosette 13 CO Peaks HLC Increasing Similarity of ALL Spectra in Map

The Spectral Correlation Function as a Function of Spatial Scale (v.2.0; Padoan et al. 2001) Figure from Falgarone et al. 1994

v.2.0: Scale-Dependence of the SCF Example for “Simulated Data” Padoan, Rosolowsky & Goodman 2001 Scale Spectral Correlation Each plotted point is “mean” of distribution for that spatial lag.

How Well Do Numerical Models Match Reality, Now? 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

The Value of MHD Simulations, The Spectral Correlation Function Goal: To improve simulations enough so that they “match” observations empirically, then use the matching simulations to “experiment” with ISM conditions. Status: 1.Atomic ISM simulations much improved (Ballesteros-Paredes, Vazquez-Semadeni & Goodman 2002) 2.LMC scale height mapped (Padoan, Kim, Goodman & Stavely-Smith 2001) 3.Molecular cloud simulations ~rule out equipartition field (Padoan & Goodman 2002) Plans: Ultimately include continuum (dust) data in comparisons. Higher-resolution simulations optimized to match existing observations, will allow extrapolation into presently unobservable regimes.

Outflows Then and Now (and Then and Now and Then…) Bally, Devine, and Alten, 1996, ApJ, 473, 921.

Outflows Then and Now (and Then and Now, and Then…) 1.YSO outflows are highly episodic. 2.Much momentum and energy is deposited in the cloud (~10 44 to erg, comparable or greater than cloud K.E.). 3.Some cloud features are all outflow. That’s how much gas is shoved around! 4.Powering source of (some) outflows may move rapidly through ISM. See collected thesis papers of H. Arce. (Arce & Goodman 2001a,b,c,d; Goodman & Arce 2002).

L1448 Bachiller et al B5 Yu Billawala & Bally 1999 Lada & Fich 1996 Bachiller, Tafalla & Cernicharo 1994 “1. YSO Outflows are Highly Episodic”

Outflow Episodes Arce & Goodman 2001

A Good Guess about Episodicity

“Typical”(?!) Outflows See references in H. Arce’s Thesis 2001

“2. Much momentum and energy is deposited in the cloud (~10 44 to erg, comparable or greater than cloud K.E.).” BUT: Is there a “typical” amount? H. Arce’s Thesis 2001

“3. Some cloud features are all outflow. That’s how much gas is shoved around!” Arce & Goodman 2001; 2002

B5 Yu, Billawala, Bally, 1999 Mass-Velocity Relations can be very steep, especially in “bursty- looking” sources…

Mass-Velocity Relations in Episodic Outflows: Steep Slopes result from Summed Bursts Power-law Slope of Sum = -2.7 (arbitrarily >2) Slope of Each Outburst = -2 as in Matzner & McKee 2000 Arce & Goodman 2001

“4. Powering source of (some) outflows may move rapidly through ISM.” Goodman & Arce 2002

“Giant” Herbig-Haro Flow in PV Ceph Reipurth, Bally & Devine pc

PV Ceph: Episodic ejections from precessing or wobbling moving source Implied source motion ~7 km/s (3 mas/year) assuming jet velocity ~100 km/s Goodman & Arce 2002

“4. Powering source of (some) outflows may move rapidly through ISM.” Goodman & Arce 2002

HST WFPC2 Overlay: Padgett et al Arce & Goodman 2002

Goodman & Arce 2002 Trail & Jet

How Many Outflows are There at Once? What is their cumulative effect?

Action of Outflows(?) in NGC 1333 SCUBA 850  m Image shows N dust (Sandell & Knee 2001) Dotted lines show CO outflow orientations (Knee & Sandell 2000)

“Beyond Now” 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)

“Beyond Now” 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)

SIRTF Legacy Survey Perseus Molecular Cloud Complex (one of 5 similar regions to be fully mapped in far-IR by SIRTF Legacy)

SIRTF Legacy Survey MIRAC Coverage 2 degrees ~ 10 pc

Un(coordinated) Molecular-Probe Line, Extinction and Thermal Emission Observations Molecular Line Map Nagahama et al CO (1-0) Survey Lombardi & Alves 2001Johnstone et al. 2001

More Probes ≠ More Confusion 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

B68

Observing Then & Now 1 day for a 13 CO map then 1 minute for a 13 CO map now

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

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).

Outflows Magnetohydrodynamic Waves Thermal Motions MHD Turbulence Inward Motions SNe/GRB H II Regions “We should not hire a star formation theorist. Star formation is too messy a problem, and will never be solved. It’s not worthy of a theorist.”

Star Formation Then and Now 1.How does one calculate the long-term efficiency of star formation in realistic galactic molecular clouds, and can that calculation explain the extragalactic “Schmidt Law”? –Does energy injection from episodic outflows matter? –How do clouds end? Are they sheared to bits? Torn up by outflows? –Is the IMF really universal? Is it determined by turbulence alone? –Is magnetic field strength important? –How much damage do HII regions & explosions do to realistic clouds? –How long does all of this take? The big question, and its descendants, for unworthy theorists (and observers!):

Breaking the (Schmidt) Law?? “A very approximate parameterization at best.” –Kennicutt 1998 log (Star Formation Rate) log (Total Surface Density) log (Star Formation Rate) 100% /10 8 yr 1% /10 8 yr 10% /10 8 yr log (Total Surface Density)

Cometary Core? Goodman & Arce 2002