Transcript PPT Only - Harvard-Smithsonian Center for Astrophysics

A (More) Dynamic View of
Star Formation
Alyssa A. Goodman
Harvard-Smithsonian Center for Astrophysics
Physicist’s Glossary
for Alyssa Goodman’s Talk at Rochester, 10/15/03
1 parsec = 1 pc = 3 x 1018 cm ≈ 3 light years = typical size scale for a
“dark cloud”
1 solar mass = 2 x 1033 g
age of the Sun (and ~the Earth) ~3 x 109 yr
age of the Universe ~15 x 109 yr
“extinction” = absorption+scattering (measure of how many photons
are “missing”)
“molecular cloud” = condensation of molecular hydrogen (H2) in the
interstellar medium (typically colder & denser than surroundings)
“H II region” blob of ionized hydrogen (free protons & electrons,
a.k.a. H II) surrounding hot young star
COMPLETE = COordinated Molecular Probe Line Extinction Thermal
Emission Survey (begun 2001)
IRAS = Infrared Astronomy Satellite (1983)
SIRTF = Space Infrared Telescope Facility (launched 8/03)
“Speeding Young Stars”
• The quasi-static theory of star formation
• What stays still long enough for that?
– not PV Ceph!
• Dynamic Star Formation
• How can we measure it (COMPLETE)
• What might it mean?
Star Formation
"Cores" and
Outflows
3 light years
Molecular or
Dark Clouds
Jets and
Disks
Extrasolar System
Quasi-Static
Outflow is
steady, and
lasts >>0.1 Myr
3 light years
Core formation
time
>> 1 Myr
"Cores" and
Outflows
Molecular or
Dark Clouds
Jets and
Disks
Extrasolar System
Planet formation
time ~1 Myr
Accretion onto
disk lasts~same
time as flow
(>>0.1 Myr)
Theory
Shu, Adams & Lizano 1987
Observation
Next slide shows near-IR
1000x zoom on blobs like these
E.E. Barnard, 5.5 hour exposure at Yerkes Observatory, 1907 Jan. 9
“Quiet” Taurus
Hubble Space Telescope
Near-IR Images
of Disks/Jets
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(c. 1998)
DG Tau B
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Haro 6-5B
IRAS 04302+2247
Color shows far-IR Dust Emission from IRAS
E.E. Barnard ~5.5. hour exposure at Yerkes Observatory, c. 190
Barnard’s Taurus
Barnard’s Taurus
Color shows far-IR Dust Emission from IRAS
How do we see this move?
The Oschin telescope,
48-inch aperture wide-field
Schmidt camera at
Palomar
Red Plate, Digitized Palomar Observatory Sky Survey
Measuring Motions: Molecular Line Maps
Spectral Line Observations
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
Watching the Gas Move: Spectral Line Mapping
Data cubes are in position-position-velocityintensity space
– Very hard to visualize
Measurable with spectral line mapping
–
–
–
–
–
–
centroid velocity
line width (velocity dispersion)
rotation
infall
outflow
higher-order statistical properties of the flow (e.g.
SCF)
“Spectral-Line
Map”
color in background shows
“integrated” intensity
Simulated spectral-line map, based on work of Padoan, Nordlund, Juvela, et al.
Excerpt from realization used in Padoan, Goodman &Juvela 2003
Integrated Intensity Does not Show Velocity Information
Radio Spectral-Line Survey
Alves, Lada & Lada 1999
Watching the Gas Move: Spectral Line Mapping
Data cubes are in position-position-velocity-intensity
space
– Very hard to visualize
Measurable with spectral line mapping
–
–
–
–
–
–
centroid velocity
line width (velocity dispersion)
rotation
infall
outflow
higher-order statistical properties of the flow (e.g. SCF)
The Taurus Dark Cloud Complex
Size of whole
map shown in
next slide
Mizuno et al. 1995 13CO(1-0) integrated intensity map from Nagoya 4-m
Young star positions courtesy L. Hartmann
“Coherent Dense Cores”
Islands of Calm in a Turbulent Sea
Size of whole
map shown in
next slide
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
Coherent Cores: 0.1 pc Islands of (Relative) Calm
“Dark Cloud”
Notice typical velocity “Coherent Core”
disperson on pc scales
TMC-1C, OH 1667 MHz
TMC-1C, NH (1, 1)
is ~1 km s-1
=(0.25±0.02)T
Dv
3
-0.10±0.05
intrinsic
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
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7
8
9
1
TA [K]
Order from Chaos
~0.1 pc
(in Taurus)
Order; N~R0.9
Chaos; N~R0.1
Goodman et al. 1998
Stars Form in Islands of Calm
in a Turbulent Sea
"Rolling Waves" by KanO
Tsunenobu © The Idemitsu
Museum of Arts.
Star Formation
"Cores" and
Outflows
3 light years
Molecular or
Dark Clouds
Jets and
Disks
Extrasolar System
Young Stellar Outflows in
General
and PV Ceph in particular
Spectral Line Outflow Mapping
Usually…
In Extreme Cases…
1.0
0.8
1.0
1.0
0.6
0.8
0.8
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20
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(All the) Maps of “Giant” Outflows, c. 2002
Greyscale shows ambient 1000 ptcl/cc gas
Red shows 100 ptcl/cc gas moving away from us
Blue shows 100 ptcl/cc gas moving toward us
See references in H. Arce’s Thesis 2001
(All the) Maps of “Giant” Outflows, c. 2002
See references in H. Arce’s Thesis 2001
B5
Yu, Billawala & Bally 1999
Bachiller et al. 1990
L1448
Lada & Fich 1996
Bachiller, Tafalla & Cernicharo 1994
YSO Outflows
are Highly Episodic
Outflow Episodes:Position-Velocity Diagrams
NGC2264
Figure from Arce & Goodman 2001
HH300
The Usual Questions About Outflows
• How, exactly, do they carry away
angular momentum from the forming
star?
• Can they “drive” turbulence in starforming regions?
• How are “optical” HH flows & molecular
outflows related?
• How long do they last?
• How many are there, really?
Today’s Question
What can outflows tell us about the
motion of a star relative to its
environment?
“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 2003
PV Ceph is
moving at
~20 km s-1
1 pc
Goodman & Arce 2003
The “Plasmon” Model for
Deceleration
Assumes each jet burst
begins at 350 km s-1
Precession is neglected, so
model executed in v*-vjet
plane
Goodman & Arce 2003
The Most
Subtle
Evidence for
PV Ceph’s
Motion
Goodman & Arce 2003
Deceleration
Means
Outflows Lie
About their
Age
Goodman & Arce 2003
Backtracking
1 pc
Goodman & Arce 2003
?
DSS Image of NGC 7023
100 mm IRAS Image of NGC 7023-PV Ceph Region
gap
Ejected?!!
Goodman & Arce 2003
How Much Gas Could Be Pulled Along for the Ride?
RBH [arcsec at 500 pc]
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10
5
12
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10
8 9
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9
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2
eff =(5 km s
-1
)
4
2
50 M Sun
11
20
10
2 -2
GM* /R BH = eff [cm s ]
10
3
5
2
2
1 M Sun
10
10
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eff =(1 km s
-1
)
2
Effective Bondi-Hoyle
Radius for 7 M Sun in
eff =5 km s
-1
Gas
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0.001
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0.01
RBH [pc]
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How often does this happen?
Direct Proper Motion
– RW Aur 16 km s-1, Jones & Herbig 1979
– BN object w.r.t. “I” 50 km s-1, Plambeck et al. 1995
– IRAS 16293-2422 30 km s-1, Loinard 2002
– T-Tau Sb 20 km s-1, Loinard et al. 2003
Deduced from Outflow Morphology
– B5 IRS1~10 km s-1, Bally et al. 1996*
– PV Ceph 20 km s-1, Goodman & Arce 2003
*but the possibility of motion was dismissed
Dynamic
Star
Formation
•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
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“Early” Times
“Later” Times
How to measure dynamic star
formation?
Time is a key dimension but spatial
statistics remain our best hope to
understand it.
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 Lesson of Coordination: 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 mm 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
Could we really…?
10
10
Time (hours)
10
10
3
1 day for a
map when
the 3 wise
men were 40
A V~5 mag, Resolution~1'
13CO
2
A V~30 mag, Resolution~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 mm
1 Day
1
0
1 Hour
NICER/8-m
10
1 Week
-1
1 Minute
SEQUOIA+
10
10
-2
1 minute for
the same
13CO map today
-3
SCUBA-2
1 Second
10
NICER/2MASS
-4
1980
1985
1990
1995
NICER/SIRTF
2000
Year
2005
2010
2015
The
COordinated
Molecular
Probe
Line
Extinction
Thermal
Emission
Survey
COMPLETE
Alyssa A. Goodman, Principal Investigator (CfA)
João Alves (ESA, Germany)
Héctor Arce (Caltech)
Paola Caselli (Arcetri, Italy)
James DiFrancesco (HIA, Canada)
Jonathan Foster (CfA, PhD student)
Mark Heyer (UMASS/FCRAO)
Di Li (CfA)
Doug Johnstone (HIA, Canada)
Naomi Ridge (CfA)
Scott Schnee (CfA, PhD student)
Mario Tafalla (OAS, Spain)
Tom Wilson (MPIfR)
COMPLET
E
Perseus
IRAS +
FCRAO
(73,000 13CO Spectra)
Perseus
Total Dust Column (0 to 15 mag AV)
(Based on 60/100 microns)
Dust Temperature (25 to 45 K)
(Based on 60/100 microns)
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Hot Source in a Warm Shell
Column
Density
Temperature
+
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(LZW)
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this
picture.
=
The action of
multiple
bipolar
outflows in
NGC 1333?
SCUBA 850 mm Image
shows Ndust (Sandell & Knee
2001)
Dotted lines show CO
outflow orientations (Knee &
Sandell 2000)
A (More) Dynamic View of
Star Formation
Alyssa A. Goodman
Harvard-Smithsonian Center for Astrophysics