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The Truth about Star Formation
Alyssa A. Goodman
Harvard-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?
Star Formation 101
"Cores" and
Outflows
1 pc
Molecular or
Dark Clouds
Jets and
Disks
Extrasolar System
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?
•
What is the time-history of star production in a
“cloud”? Are all the stars formed still “there”?
(Big cloud--“Starless” Core--Outflow--Planet
Formation--Clearing)
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 wavelengthsdust
grain sizes, dust temperature
• Molecular spectral-line mapping (e.g. FCRAO)
– Gives gas density, temperature & velocity distrbution
• MHD Simulations
Velocity from
Spectroscopy
Observed Spectrum
Telescope 
Spectrometer
1.5
Intensity
1.0
0.5
0.0
All thanks to Doppler
-0.5
100
150
200
250
"Velocity"
300
350
400
Radio Spectral-line Observations of Interstellar Clouds
Spectral Line Observations
Radio Spectral-line Observations of Interstellar Clouds
Radio Spectral-Line Survey
Alves, Lada & Lada 199
Velocity as a "Fourth" Dimension
Spectral Line Observations
Loss of
1 dimension
Mountain Range
No loss of
information
Nagahama et al. 1998 13CO (1-0) Survey
Un(coordinated) MolecularProbe Line, Extinction and
Thermal Emission
Observations
Molecular Line
Map
2MASS/NICER Extinction Map of Orion
1:50
50
1 pc
55
2:00
2:00
05
10
10
20
15
1 pc
20
30
25
SCUBA
30
40
5:41:00
20
40
R.A. (2000)
40
42:00
SCUBA
42:00
Johnstone et al. 2001
Lombardi & Alves 2001
30
41:00
R.A. (2000)
30
Johnstone et al. 2001
5:40:00
The Best Coordinated Effort: B68
Optical
Image
Dust Emission
C18O
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
NICER
Extinction
Map
Radial Density
Profile, with Critical
Bonnor-Ebert
Sphere Fit
Star Formation 101
"Cores" and
Outflows
1 pc
Molecular or
Dark Clouds
Jets and
Disks
Extrasolar System
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?
•
What is the time-history of star production in a
“cloud”? Are all the stars formed still “there”?
(Big cloud--“Starless” Core--Outflow--Planet
Formation--Clearing)
Truth?: Part 1
Part II
Star
Formation
>>101
•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 L, G
•movie=1.4 free-fall times
Bate, Bonnell & Bromm
2002
Star Formation 101
"Cores" and
Outflows
1 pc
Molecular or
Dark Clouds
Jets and
Disks
Extrasolar System
(Synthesizing) the right “starting” condition
b=0.01
Stone, Gammie & Ostriker 1999
[T / 10 K]
b=[
2
-3
nH / 100 cm ][ B / 1.4 G]
2
b=1
•Driven Turbulence; M K; no gravity
•Colors: log density
•Computational volume: 2563
•Dark blue lines: B-field
•Red : isosurface of passive contaminant after saturation
Evaluating Synthesized
Spectral Line Map of
MHD Simulations:
The Spectral
Correlation Function
(SCF)
Simulated map, based on work of Padoan, Nordlund, Juvela, et al.
Excerpt from realization used in Padoan & Goodman 2002.
Falloff of Correlation with Scale
How Well can Molecular Clouds be Modeled, Today?
Summary Results from SCF Analysis
“Equipartition”
Models
“Reality”
“Stochastic”
Models
Scaled
“Superalfvenic”
Models
Magnitude of Spectral Correlation at 1 pc
Padoan,
Goodman
& Juvela 2002
Star Formation 101
"Cores" and
Outflows
1 pc
Molecular or
Dark Clouds
Jets and
Disks
Extrasolar System
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)
AMR Simulation
Simulated NH3 Map
Berkeley Astrophysical Fluid Dynamics Group
http://astron.berkeley.edu/~cmckee/bafd/results.html
Barranco & Goodman 1998
Observed ‘Starting’ Cores: 0.1 pc Islands of (Relative) Calm
“Dark Cloud”
“Coherent Core”
TMC-1C, OH 1667 MHz
TMC-1C, NH 3 (1, 1)
-0.10±0.05
D v intrinsic =(0.25±0.02)T
1
9
8
8
7
7
-1
]
9
D v intrinsic [km s
-1
D v [km s ]
Velocity Dispersion
1
A
6
5
4
5
4
3
3
Dv=(0.67±0.02)T
2
6
-0.6±0.1
A
2
3
4
5
6
7
8
9
2
6
7
1
TA [K]
Goodman, Barranco, Wilner & Heyer 1998
8
9
2
3
0.1
Size Scale
4
5
6
7
8
9
1
TA [K]
Cores = Order from Chaos
~0.1 pc
(in Taurus)
Order; N~R0.9
Chaos; N~R0.1
Star Formation 101
"Cores" and
Outflows
1 pc
Molecular or
Dark Clouds
Jets and
Disks
Extrasolar System
“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
Complications
Observing Biases
Temporal Behavior
Regional Variations
Perseus in
(Warmish)
Dust
Perseus in
(Coldish)
Molecular
Gas
Temporal Evolution
10
0
Power-law Slope of Sum = -2.7
(arbitrarily >2)
10
Slope of Each Outburst = -2
-1
Mass [Msun]
as in Matzner & McKee 2000
10
10
10
10
-2
-3
-4
-5
2
0.1
3
4 5 6 78
2
3
1
4
5 6 78
2
10
Velocity [km s-1]
Example 1: Episodicity changes
Energy/Momentum Deposition (time)
Example 2: (Some) Young
stars may zoom through ISM
1. Episodic Outflows:
Steep Mass-Velocity Slopes Result from Summed Bursts
10
0
Power-law Slope of Sum = -2.7
(arbitrarily >2)
Mass [Msun]
10
10
10
10
10
Slope of Each Outburst = -2
-1
as in Matzner & McKee 2000
-2
-3
-4
-5
2
0.1
3
4 5 6 78
2
3
1
4
5 6 78
2
10
Velocity [km s-1]
Arce & Goodman 2001b
Example 2: Powering source of (some)
outflows may zoom through ISM
“Giant”
HerbigHaro Flow
from
PV Ceph
1 pc
Image from Reipurth, Bally & Devine 1997
PV Ceph
Episodic ejections
from a precessing or
wobbling moving
source
Goodman & Arce 2002
PV Ceph is
moving at
~10 km s-1
Goodman & Arce 2002
4x 10
“Plasmon” Model of PV Ceph
18
500x10
70
15
3
60
Star
Distance along x-direction (cm)
y k not positions (cm)
2
Star-Knot
Difference
(%)
50
300
Star-Knot
Difference
40
30
200
1
Knot Offset/Star Offset (Percent)
400
20
Knot
100
Initial jet 250 km s1; star motion 10
km s-1
0
-4x 10
17
-2
10
0
0
5
10
15x10
3
0
0
x k not posns. w.r.t. star "now" (c m)
Elapsed Time since Burst (Years)
Goodman & Arce 2002
4x 10
“Plasmon” Model of PV Ceph
18
10
9
8
3
"Dynamical Time"/Elapsed Time
y k not positions (cm)
7
2
6
5
4
3
2
1
1
0.0
0.5
1.0
1.5
2.0
2.5
3.0x10
18
Distance of Knot from Source (cm)
0
-4x 10
17
-2
0
x k not posns. w.r.t. star "now" (c m)
Goodman & Arce 2002
Complications
Observing Biases
Temporal Behavior
Regional Variations
Nagahama et al. 1998 13CO (1-0) Survey
Molecular Line
Map
“Regional Variations?”
2MASS/NICER Extinction Map of Orion
1:50
50
1 pc
55
2:00
2:00
05
10
10
20
15
1 pc
20
30
25
SCUBA
30
40
5:41:00
20
40
R.A. (2000)
40
42:00
SCUBA
42:00
Johnstone et al. 2001
Lombardi & Alves 2001
30
41:00
R.A. (2000)
30
Johnstone et al. 2001
5:40:00
Truth?: Part 1
Part II
The
COordinated
Molecular
Probe
Line
Extinction
Thermal
Emission
Survey
COMPLETE
sampling as a path to missing truths
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)
5 degrees (~tens of
pc)
COMPLETE,
Part 1
SIRTF Legacy
Coverage of
Perseus
Observations:
2003-- Mid- and Far-IR SIRTF Legacy Observations: dust temperature and
>10-degree scale NearIR Extinction, Molecular
Line and Dust Emission
Science:
Surveys of Perseus,
Ophiuchus & Serpens
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
–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
(Lee, Myers & Tafalla 2001).
COMPLE
TE, Part 2
(2003-5)
FCRAO N2H+ map with CS spectra superimposed.
Observations, using target list generated from Part 1:
<arcminute-scale core
maps to get density &
Science:
velocity structure all the
way from >10 pc to 0.01
pc
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
Multiplicity/fragmentation studies
Detailed modeling of pressure structure on <0.3 pc scales
Searches for the "loss" of turbulent energy (coherence)
Is this Really Possible Now?
10
A V~5 mag, Resolution~1'
3
1 day for a
map then
A V~30 mag, Resolution~10"
13CO
10
Time (hours)
10
10
13
CO Spectra for 32 Positions
in a Dark Cloud (S/N~3)
Sub-mm Map of a Dense Core
at 450 and 850 m
2
1 Day
1
0
1 Hour
NICER/8-m
10
1 Week
-1
1 Minute
SEQUOIA+
10
10
-2
1 minute for a
13CO map now
SCUBA-2
-3
1 Second
10
NICER/2MASS
-4
1980
1985
1990
1995
NICER/SIRTF
2000
Year
2005
2010
2015
COMPLETE Preview:
Discovery of a Heated Dust Ring in Ophiuchus
2 pc
Goodman, Li & Schnee 200
…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’ Role
Evaluation of Constructive/Destructive Role of
Explosions/Winds
Tracking down progeny (includes USNO-B work)
Extra Slides
COMPLETE:
JCMT/SCUBA
>10 mag A
V
8
6
4
2
~100 hours at
SCUBA
10 pc
10 pc
Ophiuchus
Perseus
Johnstone, Goodman & the
COMPLETE team, SCUBA
2003(?!)
L1448
Bachiller, Tafalla & Cernicharo 1994
YSO Outflows
are Highly Episodic
B5
Yu Billawala & Bally 1999
Bachiller et al. 1990
Lada & Fich 1996
Position-Velocity Diagrams show
Outflow Episodes:Position-Velocity Diagrams
NGC2264
Figure from Arce & Goodman 200az1a
HH300
• Slope steepens when t
corrections made
– Previously unaccounted-for
mass at low velocities
• Slope often (much) steeper
than “canonical” -2
• Seems burstier sources have
steeper slopes?
Mass/Velocity
“Steep” Mass-Velocity
Relations
-3
-8
Velocity
-4
-8
HH300 (Arce & Goodman 2001a)
How much gas will be pulled along for the ride?
Goodman & Arce 2002
Just how fast
is PV Ceph
going?