Future Directions in High Resolution Astronomy:
A Celebration of the 10th Anniversary of the VLBA
A Birth and Growth of
a Collimated Molecular Jet from an AGB Star
Hiroshi Imai
(Joint Institute for VLBI in Europe, NL)
Philip J. Diamond
(Jodrell Bank Observatory, UK)
• Water fountains: cites of stellar jet’s birth
• W43A: an AGB star having a jet and an envelope
• Implication of the W43A jet
The Great Barrier Dam, the Netherlands
Jet formation in final stellar evolution
• Central objects of planetary nebulae (PNe)
= post-AGB stars
– Bipolar jets (>100 km/s, >> 1000K, ionized)
– Producing complicated PN morphology
Jet from a planetary nebula: Henize 2-90 (Sahai & Nyman 2000)
Jet formation in final stellar evolution
When such stellar jets are launched ?
How to launch such stellar jets ?
Jet from a planetary nebula: Henize 2-90 (Sahai & Nyman 2000)
High velocity stellar molecular flows
Jet
Outflow
• Before finding
optical jet
• Dragged by a
(unseen) collimated jet
Outflow in
OH 231.8+4.2
(Alcolea et al. 2001)
High velocity stellar molecular flows
What is
the central star?
White dwarf ?
Mira star ?
or young star ?
Outflow in
OH 231.8+4.2
(Alcolea et al. 2001)
Transition from AGB to post-AGB
• A Mira variable
(AGB star):
– Pulsation
– Spherical
envelope
– Small bipolarity
– Slow wind
(~10 km/s)
Spherical
circumstellar
envelope:
around RT Virginis
(Imai et al. 2003,
Transition from AGB to post-AGB
A Mira-star
envelope is
transformed to a
collimated jet
smoothly ?
Spherical
circumstellar
envelope:
around RT Virginis
(Imai et al. 2003,
Water fountains: cites of
on-going
jet
formation
W43A
IRAS
19134+2131
IRAS
16342-3814
• V(H2O) >= 100 km/s
>> V(OH) =< 30 km/s
• Clear double peaks
• Symmetric with respect to
the systemic velocity
High velocity H2O maser sources
(Likkel et al. 1992)
Water fountains: cites of
on-going
jet
formation
W43A
IRAS
19134+2131
IRAS
16342-3814
• Newly-formed jets or
extreme super winds ?
• How old ?
• How to produce ?
• Young stellar objects ?
High velocity H2O maser sources
(Likkel et al. 1992)
VLBA observations of
the W43A H2O/OH masers
• H2O masers:
Jun. 1994, Oct. 1994, Mar. 1995,
Apr. 2002, Jul. 2002, Nov. 2002,
Apr. 2003, ..... (now going on)
Synthesized beam: ~0.5 mas
Velocity resolution: 0.2 km/s
• OH masers (1612, 1665 & 1667MHz):
Jun. 1994, Oct. 1994, Mar. 1995,
Dec. 2001, Aug. 2002, ..... (now going on)
Synthesized beam: ~9 mas
Velocity resolution: 0.45 km/s
History of the W43A jet
Birth of the molecular jet
(at my birthday?)
Discovery of
the high-velocity masers
Destruction of
the molecular jet
(at the end of my life?)
(Genzel & Downes 1977)
Discovery of the molecular jet
VLBA operation
(Imai et al. 2002)
(Since 1993)
OH maser
observations
(5 epochs)
1970
1980
1990
H2O maser
observations
(7 epochs)
2000
2010
2020
2030....
Highly-collimated jet of molecular gas
The first one year:
Imai, Obara, Diamond, Omodaka, & Sasao 2002
Jet parameters (1994 - 1995)
Imai et al. (2002)
100
21 proper motions
Decl. offset (mas)
0
-100
-200
119 - 126 km/s
114 - 117 km/s
-3 - 0 km/s
-8 - -7 km/s
-50 - -46 km/s
-57 - -50 km/s
-300
100
0
-100
Proper motion
100 km/s
-200
-300
-400
-500
-600
R.A. offset (mas)
• 3D jet speed: 145 +/-20 km/s in major axis
• Standard deviation ratio:
V(jet)/V(internal) = 9.5 +/-4.1 (variance-covariance
analysis)
-700
Jet parameters (1994 - 1995)
Imai et al. (2002)
100
21 proper motions
Decl. offset (mas)
0
-100
-200
119 - 126 km/s
114 - 117 km/s
-3 - 0 km/s
-8 - -7 km/s
-50 - -46 km/s
-57 - -50 km/s
-300
100
0
-100
Proper motion
100 km/s
-200
-300
-400
-500
-600
-700
R.A. offset (mas)
• Jet alignment: length = 1700 AU, P.A.= 69.3±0.3 deg.
• Cluster alignment: length = 250, 350 AU, width < 30 AU
P.A.= 54.6+/-6.0 deg., 57.2+/-0.3 deg. (red, blue clusters)
H2O maser kinematics in 2002
Imai & Diamond (2003)
Growth of the molecular jet
• Growth rate of jet ~ 300AU/ 8 years ~ 180 km/s
• Birth of the jet around the year 1970
A precessing jet model
Point symmetry
Constant-velocity
motion of each
maser cloud
Interaction with the
ambient envelope
A precessing jet model
Straight alignments
with axis offsets
>>> lifetime of
maser clouds
~ 10 years
The W43A jet is precessing !
Period ~ 55 years
Amplitude ~ 5 degrees
Inclination ~ 39 degrees
500
Y (AU)
250
0
-250
-500
Maser spot (Oct. 1994)
Precessing jet model (1994.8)
1000
500
0
X (AU)
-500
-1000
The precession is true !
A consistent model at every epoch
>>> direct estimation: d (~2.6 kpc),
origin location, and jet ignition time (~30 yr ago)
500
Maser spot (Apr. 2002)
Precessing jet model (2002.3)
Y (AU)
250
0
-250
-500
Maser spot (Oct. 1994)
Precessing jet model (1994.8)
1000
500
0
X (AU)
-500
-1000
What star is
W43A ?
An AGB star!
Signatures of an pulsating star
Periodic flux variation (P~ 400 d) in OH 1612 MHz masers
(Harman & Habing 1985; van Langevelde et al. 1990)
Dwingeloo 25-m telescope
Spherically-expanding envelope
• The same systemic velocity of
the H2O and OH masers (VLSR ~ 34 km/s)
• Similar to Mira OH maser sources
150
100
100
50
0
1994 October 10
Decl. offset (mas)
Decl. offset (mas)
1994 June-October
0
-50
OH masers
300
42 - 44 km/s
38 - 42 km/s
25 - 30 km/s
250
200
118 - 126 km/s
114 - 118 km/s
-8 - 0 km/s
-51 - -46 km/s
-57 - -51 km/s
-200
-300
-100
-150
-100
100
0
-100
500 AU @2.6 kpc
-200
-300
-400
R.A. offset (mas)
150
100
R.A. offset (mas)
50
0
1612 MHz OH masers
-500
-600
-700
Spherically-expanding envelope
• The same systemic velocity of
the H2O and OH masers (VLSR ~ 34 km/s)
• Dynamical time scale of the envelope ~ 260 years
150
1994 June-October
100
Decl. offset (mas)
50
0
-50
OH masers
-100
-150
300
42 - 44 km/s
38 - 42 km/s
25 - 30 km/s
250
200
150
100
R.A. offset (mas)
50
0
Distance - velocity diagram
When is a stellar jet launched?
H2O masers and a jet in PPN
(Miranda et al. 2001)
• Mira stars:
– Elongation of
circumstellar envelop
(Elitzur et al. 2003)
– by jets ? or by others?
• OH/IR stars:
–
–
–
–
Super winds (~1000 years)
H2O maser jets: < 100 years
Later outflows, optical jets
H2O maser segments in
PPNs
Morphology of
planetary nebulae
Determined by
the envelope morphology
at AGB phase,
created by a stellar jet !
Water fountains = Molecular jets
W43A
Imai, & Diamond 2003
IRAS
19134+2131
IRAS
16342-3814
UH88+Sirius image
(Deguchi & Nakashima 2002)
Water fountains = Molecular jets
W43A
IRAS
19134+2131
Morris, Sahai & Claussen 2003
IRAS
16342-3814
HST image (Sahai et al. 1999)
Water fountains = Molecular jets
W43A
IRAS
19134+2131
Imai, Morris & Sahai 2003
IRAS
16342-3814
3-D jet speed: ~120 km/s
Dynamical time scale ~ 90 years
2MASS All Sky Survey image
Water fountains = Molecular jets
W43A
IRAS
19134+2131
IRAS
16342-3814
Similar
sizes (2000 - 4000 AU)
and
dynamical time scales
(< 100 years)
of the molecular jets !
Duration of molecular jet
in the earliest phase of
stellar jets: ~ 100 years
A molecular jet in W43A
was born with me and
will disappear with me!
A sensational chance in my life!
The Prince Charles, visiting in the MERLIN upgrade celebration
on 28 April 2003 at Jodrell Bank Observatory, UK
Schematic cartoon of W43A
Thank you !
Kasteel de Haar, the Netherlands
Circumstellar envelope of W43A
Well developed, but compact ......
•Size < 10000 AU
•Mass ~ 15 Msun
(including
foreground cloud)
• Optically thin
(spectral index~3-4)
2.7 mm dust continuum
emission
(NMA observation)
(Imai et al. 2003)
20000 AU at 2.6 kpc
+
H2O & OH
masers
Circumstellar envelope of W43A
Has not be ionized yet .....
20000 AU at 2.6 kpc
+
H2O & OH
masers
UH88+Sirius
JHK-band image
(Deguchi &
Nakashima 2002)
Signatures of going mass loss
SiO maser emission
(see Nakashima & Deguchi 2003)
Rotating disk ?
e.g.
IRC -10414
(Imai et al. 1999)
NML Cyg
(Boboltz & Marvel 1999)
OH 231.8+4.2
(Sanchez Contreras et al.
2002)