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
1.0
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-0.5
Inte
nsit
y
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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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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
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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v [
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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v
intr
insi
c[k
m s
-1]
6 7 8 90.1
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TA [K]
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]
0.12 3 4 5 6 7 8
12 3 4 5 6 7 8
102
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]
0.12 3 4 5 6 7 8
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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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2
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y knot positions (cm)
-4x1017
-2 0
x knot posns. w.r.t. star "now" (cm)
500x1015
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Distance along x-direction (cm)
15x103
1050
Elapsed Time since Burst (Years)
70
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0
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
3
2
1
0
y knot positions (cm)
-4x1017
-2 0
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
2:00
55
50
05
10
15
20
25
30
R.A. (2000)
1 pc
SCUBA
5:40:003041:003042:00
2:00
1:50
10
20
30
40
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
990
B5
Yu B
illaw
ala
& B
ally
199
9
Lada &
Fic
h 1
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6
Bach
iller,
Tafa
lla &
Cern
icharo
19
94
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
-8
-4
-8M
ass
/Velo
city
Velocity
How much gas will be pulled along for the ride?
Goodman & Arce 2002
Just how fast is PV
Ceph going?