The Truth about Star Formation

Alyssa A. GoodmanHarvard-Smithsonian Center for Astrophysics

cfa-www.harvard.edu/~agoodman

The Truth about Star Formation

We have a pretty good idea, but not a clear picture of how stars like the Sun form.(Today’s “truth”)

How well we understand the formation of massive stars depends on who you ask.Is the radiation pressure limit surmountable?

Mergers & Aquisitions

Are there accretion disks involved at all?Has a bipolar flow really been seen from a

massive star?

Molecular or Dark Clouds

"Cores" and Outflows

Star Formation 101

Jets and Disks

Extrasolar System

1 p

c

The Whole Truth

Quests for Truth, 2002• How do processes in each stage impact

upon each other? (Sequential star formation, outflows reshaping clouds…)

• How long do “stages” last and how are they mixed? (Big cloud--“Starless” Core--Outflow--Planet Formation--Clearing)

• What is the time-history of star production in a “cloud”? Are all the stars formed still “there”?

Tools for Truth• Optical imaging (e.g. HST)

– Extinction, reddening dust grain sizes, dust column density distribution

– Shocked gas (e.g. HH jets)

• Near-infrared imaging (e.g. SIRTF)– Same as optical, plus reveals deeply “embedded”

young sources

• Thermal dust imaging (e.g. JCMT/SCUBA)– Cold dust “glows” at far-IR and sub-mm

wavelengthsdust grain sizes, dust temperature

• Molecular spectral-line mapping (e.g. FCRAO)– Gives gas density, temperature & velocity

distrbution

• MHD Simulations

1.5

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"Velocity"

Observed Spectrum

Telescope Spectrometer

All thanks to Doppler

Velocity from Spectroscopy

Radio Spectral-line Observations of Interstellar Clouds Spectral Line Observations

Alves, Lada & Lada 1999

Radio Spectral-Line Survey

Radio Spectral-line Observations of Interstellar Clouds

Velocity as a "Fourth" DimensionSpectral Line Observations

Mountain RangeNo loss ofinformatio

n

Loss of1 dimension

2MASS/NICER Extinction Map of Orion

Un(coordinated) Molecular-Probe Line,

Extinction and Thermal Emission Observations

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1 pc

SCUBA

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R.A. (2000)

1 pc

SCUBA

Molecular Line Map

Nagahama et al. 1998 13CO (1-0) Survey

Lombardi & Alves 2001Johnstone et al. 2001 Johnstone et al. 2001

The Best Coordinated Effort: B68

C18ODust EmissionOptical 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 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

Molecular or Dark Clouds

"Cores" and Outflows

Star Formation 101

Jets and Disks

Extrasolar System

1 p

c

Quests for Truth, 2002• How do processes in each stage impact

upon each other? (Sequential star formation, outflows reshaping clouds…)

• How long do “stages” last and how are they mixed? (Big cloud--“Starless” Core--Outflow--Planet Formation--Clearing)

• What is the time-history of star production in a “cloud”? Are all the stars formed still “there”?

Truth?: Part 1

Part II

Star Formation

>>101

Bate, Bonnell & Bromm 2002

•MHD turbulence gives “t=0” conditions; Jeans mass=1 Msun

•50 Msun, 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

Molecular or Dark Clouds

"Cores" and Outflows

Star Formation 101

Jets and Disks

Extrasolar System

1 p

c

(Synthesizing) the right “starting” condition

Stone, Gammie & Ostriker 1999•Driven Turbulence; M K; no gravity•Colors: log density•Computational volume: 2563

•Dark blue lines: B-field•Red : isosurface of passive contaminant after saturation

=0.01 =1

T / 10 K

nH 2 / 100 cm-3 B / 1.4 G 2

Simulated map, based on work of Padoan, Nordlund, Juvela, et al.Excerpt from realization used in Padoan & Goodman 2002.

Evaluating Synthesized Spectral

Line Map of MHD Simulations: The

Spectral Correlation

Function (SCF)

“Equipartition”Models

How Well can Molecular Clouds be Modeled, Today?Summary Results from SCF Analysis

Fallo

ff o

f C

orr

ela

tion

wit

h S

cale

Magnitude of Spectral Correlation at 1 pc

Padoan, Goodman

& Juvela 2002

“Reality”

Scaled “Superalfvenic”Models

“Stochastic”Models

Molecular or Dark Clouds

"Cores" and Outflows

Star Formation 101

Jets and Disks

Extrasolar System

1 p

c

Cores: Islands of Calm in a Turbulent Sea?

"Rolling Waves" by KanO Tsunenobu © The Idemitsu Museum of Arts.

Islands of Calm in a Turbulent Sea

Goodman, Barranco, Wilner & Heyer 1998

Islands (a.k.a. Dense Cores)

Berkeley Astrophysical Fluid Dynamics Grouphttp://astron.berkeley.edu/~cmckee/bafd/results.html Barranco & Goodman 1998

AMR Simulation

Simulated NH3 Map

Goodman, Barranco, Wilner & Heyer 1998

Observed ‘Starting’ Cores: 0.1 pc Islands of (Relative) Calm

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km s-1

]

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TA [K]

TMC-1C, OH 1667 MHz

v=(0.67±0.02)TA-0.6±0.1

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-1]

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TMC-1C, NH3 (1, 1)

vintrinsic=(0.25±0.02)T A-0.10±0.05

“Coherent Core”“Dark Cloud”

Size Scale

Velo

city

Dis

pers

ion

Cores = Order from Chaos

Order; N~R0.9

~0.1 pc(in Taurus)

Chaos; N~R0.1

Molecular or Dark Clouds

"Cores" and Outflows

Star Formation 101

Jets and Disks

Extrasolar System

1 p

c

“Giant” Outflows

See references in H. Arce’s Thesis 2001

Does fecundity = demise?

Bipolar outflows from young stars

Stellar Winds from older stars

Large Explosions (SNe, GRBs)

All have the power both to create & destroy

The action of multiple outflows in NGC 1333?

SCUBA 850 mm Image shows Ndust (Sandell & Knee

2001)Dotted lines show CO

outflow orientations (Knee & Sandell 2000)

Action of Stellar Winds

Great Bubble in Perseus

QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.

Complications

Observing Biases

Temporal Behavior

Regional Variations

Perseus in (Warmish)

DustQuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.

Perseus in (Coldish) Molecular

Gas

Temporal Evolution

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Mass

[M

sun]

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Velocity [km s-1]

Power-law Slope of Sum = -2.7(arbitrarily >2)

Slope of Each Outburst = -2as in Matzner & McKee 2000

Example 1: Episodicity changes Energy/Momentum Deposition (time)

Example 2: (Some) Young stars may zoom through

ISM

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Mass

[M

sun]

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Velocity [km s-1]

1. Episodic Outflows: Steep Mass-Velocity Slopes Result from Summed

Bursts

Power-law Slope of Sum = -2.7(arbitrarily >2)

Slope of Each Outburst = -2as in Matzner & McKee 2000

Arce & Goodman 2001b

Example 2: Powering source of (some) outflows may zoom through ISM

1 pc

“Giant” Herbig-

Haro Flow from

PV Ceph

Image from Reipurth, Bally & Devine 1997

PV Ceph

Episodic ejections from a

precessing or wobbling

moving moving source

Goodman & Arce 2002

PV Ceph is moving at ~10 km s-1

Goodman & Arce 2002

“Plasmon” Model of PV Ceph4x1018

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y knot positions (cm)

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x knot posns. w.r.t. star "now" (cm)

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Distance along x-direction (cm)

15x103

1050

Elapsed Time since Burst (Years)

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Knot Offset/Star Offset (Percent)

Knot

Star

Star-KnotDifference

Star-KnotDifference

(%)

Initial jet 250 km s-1; star motion

10 km s-1

Goodman & Arce 2002

“Plasmon” Model of PV Ceph4x1018

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2

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y knot positions (cm)

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x knot posns. w.r.t. star "now" (cm)

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"Dynamical Time"/Elapsed Time

3.0x1018

2.52.01.51.00.50.0

Distance of Knot from Source (cm)

Goodman & Arce 2002

Complications

Observing Biases

Temporal Behavior

Regional Variations

2MASS/NICER Extinction Map of Orion

“Regional Variations?”

5:41:0040 20 40 42:00

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R.A. (2000)

1 pc

SCUBA

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R.A. (2000)

1 pc

SCUBA

Molecular Line Map

Nagahama et al. 1998 13CO (1-0) Survey

Lombardi & Alves 2001Johnstone et al. 2001 Johnstone et al. 2001

Truth?: Part 1

Part II

COMPLETEsampling as a path to missing truths

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 (HIA, Canada)Mark Heyer (UMASS/FCRAO)

Doug Johnstone (HIA, Canada)Scott Schnee (CfA, PhD student)

Mario Tafalla (OAS, Spain)Tom Wilson (MPIfR/SMTO)

COMPLETE, Part 1

Observations:2003-- Mid- and Far-IR SIRTF Legacy Observations: dust temperature and column density maps ~5 degrees mapped with ~15" resolution (at 70 m)

2002-- NICER/2MASS Extinction Mapping: dust column density maps ~5 degrees mapped with ~5' resolution

2003-- SCUBA Observations: dust column density maps, finds all "cold" source ~20" resolution on all AV>2”

2002-- FCRAO/SEQUOIA 13CO and 13CO Observations: gas temperature, density and velocity information ~40" resolution on all AV>1

Science:– Combined Thermal Emission data: dust spectral-energy distributions, giving emissivity, Tdust and Ndust

– Extinction/Thermal Emission inter-comparison: unprecedented constraints on dust properties and cloud distances, in addition to high-dynamic range Ndust map

– Spectral-line/Ndust Comparisons Systematic censes of inflow, outflow & turbulent motions enabled

– CO maps in conjunction with SIRTF point sources will comprise YSO outflow census

5 degrees (~tens of pc)

SIRTF Legacy Coverage of Perseus

>10-degree scale Near-IR Extinction, Molecular Line and

Dust Emission Surveys of Perseus, Ophiuchus

& Serpens

COMPLETE, Part 2

(2003-5)

Observations, using target list generated from Part 1:NICER/8-m/IR camera Observations: best density profiles for dust associated with "cores". ~10" resolution FCRAO + IRAM N2H+ Observations: gas temperature, density and velocity information for "cores” ~15" resolution

Science:Multiplicity/fragmentation studies

Detailed modeling of pressure structure on <0.3 pc scalesSearches for the "loss" of turbulent energy (coherence)

FCRAO N2H+ map with CS spectra superimposed.

(Le

e,

Mye

rs &

Ta

falla

20

01

).

<arcminute-scale core maps to get density & velocity structure all the way from >10 pc

to 0.01 pc

Is this Really Possible Now?

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Time (hours)

20152010200520001995199019851980

Year

1 Hour

1 Minute

1 Day

1 Second

1 Week

SCUBA-2

SEQUOIA+

NICER/8-m

NICER/SIRTFNICER/2MASS

AV~5 mag, Resolution~1'

AV~30 mag, Resolution~10"

13CO Spectra for 32 Positions in a Dark Cloud (S/N~3)

Sub-mm Map of a Dense Core at 450 and 850 m

1 day for a 13CO map then

1 minute for a 13CO map now

COMPLETE Preview:Discovery of a Heated Dust Ring in

Ophiuchus

Goodman, Li & Schnee 2003

2 pc

…and the famous “1RXS J162554.5-233037” is right in the Middle !?

2 pc

The “COMPLETE” Truth about Star Formation, c. 2005

Statistical Evaluation of Outflows’ RoleEvaluation of Constructive/Destructive Role of

Explosions/Winds

Tracking down progeny (includes USNO-B

work)

Extra Slides

COMPLETE: JCMT/SCUBA>10 mag AV

2468

Perseus

Ophiuchus

10 pc

10 pc

Johnstone, Goodman & the COMPLETE team, SCUBA

2003(?!)

~100 hours at SCUBA

L1448

Bach

iller

et

al. 1

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B5

Yu B

illaw

ala

& B

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Lada &

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Bach

iller,

Tafa

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icharo

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Position-Velocity Diagrams

show YSO Outflows are Highly Episodic

Outflow Episodes:Position-Velocity Diagrams

Figure

fro

m A

rce &

Goodm

an 2

00

az1

a

HH300

NGC2264

“Steep” Mass-Velocity Relations

HH300 (Arce & Goodman 2001a)

• Slope steepens when corrections made– Previously unaccounted-

for mass at low velocities

• Slope often (much) steeper than “canonical” -2

• Seems burstier sources have steeper slopes?

-3

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ass

/Velo

city

Velocity

How much gas will be pulled along for the ride?

Goodman & Arce 2002

Just how fast is PV

Ceph going?