wiyn image: t.a. rector, b. wolpa and g. jacoby (noao/aura/nsf) and hubble heritage team...
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WIYN Image: T.A. Rector, B. Wolpa and G. Jacoby (NOAO/AURA/NSF) and Hubble Heritage Team (STScI/AURA/NASA)
Stars Forming in a Dynamic Interstellar Medium
Alyssa A. GoodmanHarvard-Smithsonian Center for Astrophysics
cfa-www.harvard.edu/~agoodman
Stars Forming in a Dynamic ISM
When the World Stood Still (except at the last minute)
Allowing Time to Tick, and not always start at zero– Episodic Outflows
– PV Ceph: Protostar Caught Speeding?
COMPLETE sampling as a path to the answer– Carefully-designed statistical questions– Serendipity (so far: warm dust ring around X-ray source in
Ophichus, odd velocity features in Perseus…)
Standing Still, Until the Last Minute
Global Instability (e.g. Jeans) Fragments Cloud
(hierarchically)
time~106 yearsHoyle 1953
Fragments Collapse UnderGravity into “Protostars”
time~105 years
Standing Still, Until the Last Minute
A Group of Young“Zero-Age Main Sequence”
Stars is Born
Molecular or Dark Clouds
"Cores" and Outflows
Ticking, from t=0
Jets and Disks
Extrasolar System
1 p
c
BUT…BUT…• How long does each “phase” 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”?
• How do processes in each phase impact upon each other? (Sequential star formation, outflows reshaping clouds…)
Stars Forming
in a Dynamic
ISM
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
What is 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 Simulated 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 2002
“Reality”
Scaled “Superalfvenic”Models
“Stochastic”Models
Cores: Islands of Calm in a Turbulent Sea?
"Rolling Waves" by KanO Tsunenobu © The Idemitsu Museum of Arts.
Goodman, Barranco, Wilner & Heyer 1998
Islands of Calm in a Turbulent Sea
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
Ask about velocity
gradients later
Goodman, Barranco, Wilner & Heyer 1998
Observed ‘Starting’ Cores: 0.1 pc Islands of (Relative) Calm
2
3
4
5
6
7
8
9
1
v [
km s-1
]
3 4 5 6 7 8 91
2
TA [K]
TMC-1C, OH 1667 MHz
v=(0.67±0.02)TA-0.6±0.1
2
3
4
5
6
7
8
9
1
v
intr
insi
c[k
m s
-1]
6 7 8 90.1
2 3 4 5 6 7 8 91
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
Order in a Sea of Chaos
Order; N~R0.9
~0.1 pc(in Taurus)
Chaos; N~R0.1
So, can we simulate ticking time?
• MHD Simulations give good approximation of dynamic ISM, on >>0.1 pc scales
• Physical scale (reality) of ~0.1 pc SPH simulations starting from a turbulent “t=0” is debatable (no B, T=const, etc.)
– Observations indicate relative calm just before stars form
Why care about time?
10-5
10-4
10-3
10-2
10-1
100
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 outflow’s Energy/Momentum
Deposition/time
Example 2: (Some) Young stars may zoom through
ISM
Example 1: Episodicity in Outflows
See references in H. Arce’s Thesis 2001
L1448
Bach
iller
et
al. 1
990
B5
Yu B
illaw
ala
& B
ally
199
9
Lada &
Fic
h 1
99
6
Bach
iller,
Tafa
lla &
Cern
icharo
19
94
Position-Velocity Diagrams
show YSO Outflows are Highly Episodic
Velocity
Posi
tion
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
10-5
10-4
10-3
10-2
10-1
100
Mass
[M
sun]
0.12 3 4 5 6 7 8
12 3 4 5 6 7 8
102
Velocity [km s-1]
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 = -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
Goodman & Arce 2002
HST WFPC2 Overlay: Padgett et al. 2002
Arce & Goodman 2002
Optical “cones”Elongated ~N-S
Dense gas elongated
along direction of motion
Goodman & Arce 2002
Trail & Jet
How much gas will be pulled along for the ride?
Goodman & Arce 2002
Just how fast is PV
Ceph going?
Insights from a “Plasmon” Model4x1018
3
2
1
0
y knot positions (cm)
-4x1017
-2 0
x knot posns. w.r.t. star "now" (cm)
500x1015
400
300
200
100
0
Distance along x-direction (cm)
15x103
1050
Elapsed Time since Burst (Years)
70
60
50
40
30
20
10
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
Insights from a “Plasmon” Model4x1018
3
2
1
0
y knot positions (cm)
-4x1017
-2 0
x knot posns. w.r.t. star "now" (cm)
1
2
3
4
5
6
7
8
9
10
"Dynamical Time"/Elapsed Time
3.0x1018
2.52.01.51.00.50.0
Distance of Knot from Source (cm)
Goodman & Arce 2002
Stars Forming in a Dynamic ISM
When the World Stood Still (except at the last minute)
Allowing Time to Tick, and not always start at zero– Episodic Outflows
– PV Ceph: Protostar Caught Speeding?
COMPLETE sampling as a path to the answer– Carefully-designed statistical questions– Serendipity (so far: warm dust ring around X-ray source in
Ophichus, odd velocity features in Perseus…)
2MASS/NICER Extinction Map of Orion
Un(coordinated) Molecular-Probe Line,
Extinction and Thermal Emission Observations
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
COMPLETEsampling as a path to the answer
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)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
A statistical question for COMPLETE:
How Many Outflows are
There at Once?
What is their cumulative
effect?
Action of Outflows(?) in NGC 1333
SCUBA 850 mm Image shows Ndust (Sandell & Knee 2001)
Dotted lines show CO outflow orientations (Knee & Sandell
2000)
Is this Really Possible Now?
10-4
10-3
10-2
10-1
100
101
102
103
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
…yes, it’s possible
COMPLETE: JCMT/SCUBA>10 mag AV
2468
Perseus
Ophiuchus
10 pc
10 pc
Johnstone, Goodman & the COMPLETE team, SCUBA
2003(?!)
~100 hours at SCUBA
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
WIYN Image: T.A. Rector, B. Wolpa and G. Jacoby (NOAO/AURA/NSF) and Hubble Heritage Team (STScI/AURA/NASA)
Stars Forming in a Dynamic Interstellar Medium
Alyssa A. GoodmanHarvard-Smithsonian Center for Astrophysics
cfa-www.harvard.edu/~agoodman
Core “Rotation”??
N2H+ in TMC-1C; Schnee & Goodman 2003
FWHM Gradient “Beam”
0.1
pc
Core “Rotation”??
N2H+ in TMC-1C; Schnee & Goodman 2003
Core “Rotation”??
N2H+ in TMC-1C; Schnee & Goodman 2003
Core “Rotation”??
N2H+ in TMC-1C; Schnee & Goodman 2003
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
The Value of CoordinationC18ODust 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