Asymmetric Planetary Nebulae IV

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Water Fountains in Pre-Planetary Nebulae
Hancock, New Hampshire VLBA Antenna
Mark Claussen, NRAO June 19, 2007

• Asymmetric Planetary Nebulae IV
• La Palma, Canary Islands

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Water Fountain Pre-Planetary Nebulae

• Outflow velocity of water masers extremely high
  compared to AGB radial expansion velocities
• Usually discovered serendipitously (i.e. not
  searching for high-velocity flows)
• A recent targeted survey using the Green Bank
  Telescope turned up 2 new candidate sources out
  of about 50 (large bandwidth)
• Rachel Deacons work using Southern Hemisphere
  facilities discovered a few more
• Now eleven known or candidate water fountain
  sources
• Water fountain phenomenon is one of the earliest
  stages of stellar jet emergence, in the
  pre-planetary nebula phase (or before).

June 19, 2007, APN IV
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June 19, 2007 APN IV
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Water Masers and High Angular
Resolution

• Water maser characteristics
• Excitation temperature gt 400 K
• Molecular hydrogen densities gt 109 cm-3 (for
  collisional excitation)
• And, need velocity coherence along the maser

• VLBA has superb angular resolution which allows
  proper motion studies ( lt 1 mas at 1.3 cm)
• Also allows A.U. scale structure on nearby
  objects
• Astrometric studies give basic astronomy data
  (positions, proper motion, parallax)
• 1.3 cm observations give single-epoch astrometry
  of 50 mas or better, depending on tropospheric
  correction

June 19, 2007 APN IV
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VLBA Observations of Water Masers in
IRAS16342-3814 (Claussen, Sahai, and Morris)

• Six monthly epochs of VLBA observations in 2002
• The line connecting the extreme velocities (some
  2970 mas long) has increased its length by 3 mas
• The separation change corresponds to expansion
  velocity of 105 km/s
• Water maser emission quite likely arises in
  shocks where a jet hits some molecular gas.

June 19, 2007 APN IV
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IRAS 16342-3814
Estimated Distance of 2 kpc Bipolar
protoplanetary nebula Water Fountain
Nebula Claussen, Sahai, and Morris
1000 AU
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IRAS 16342-3814
Estimated Distance of 2 kpc Bipolar
protoplanetary nebula Water Fountain Nebula
1000 AU
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Where the water masers are in IRAS16342
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Water masers on southwest side (blue-shifted.
Colors denote epoch (in time order, blue, green
red, yellow, cyan). Proper motion vector
represents 11.0 mas/yr corresponding to expansion
velocity of 105 km/s
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Water masers on northeast side (red-shifted).
Colors denote epoch (in time order, blue, green
red, yellow, cyan). The masers here with
radial velocity of 155 km/s, are symmetric with
those on the southwest side with - 65 km/s, and
these two groups are kinematically symmetric
around the systemic velocity as well.
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These are also water masers on northeast side
(red-shifted), but are not quite at the tip. The
masers here have radial velocity of 180 km/s
there were no masers during these observations
that were kinematically symmetric on the
blue-shifted side. The proper motion of these
masers are faster than the 155 km/s group (at the
tip) --- 137 km/s as compared with 105 km/s.
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HST images of IRAS191342131. The solid line
shows the position angle of the projected flow
expansion vector derived from the water masers
its length of 139 mas is equal to the separation
of the red and blue-shifted maser features (Imai,
Sahai, Morris, in the press).
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Parallax measurement of the water masers in
IRAS19134 (Imai, Sahai, and Morris, in press).
The best fit annual parallax corresponds to a
distance of D 8.0 (0.9, -0.7) kpc.
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Water Masers in OH12.8-0.9 (IRAS 18139-1816)
VLBA Observations of water masers in the water
fountain OH12.8-0.9 (from Boboltz Marvel, in
press)
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Summary of Four Water Fountain Sources Properties
Characteristic OH 12.8-0.9 W43A IRAS19134 IRAS16342
Estimated Distance 8 kpc 2.6 kpc 8 kpc 2 kpc
Angular Extent 110 mas 920 mas 140 mas 3000 mas
Linear Extent 880 AU 2400 AU 1120 AU 6000 AU
3D Outflow Velocity 58 km/s 145 km/s 89 km/s 150 km/s
Dynamical Age 90 years 50 years 40 years 125 years
Optical Lobes No No Yes Yes
Outflow Collimation 15 degrees 5 degrees 10 degrees 6 degrees
measured from trigonometric parallax of water
masers
June 19, 2007 APN IV
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IRAS191901102 Water Masers (the fifth high
resolution water fountain)
VLSR -20 --- 10 km/s
VLSR 38 --- 80 km/s
Creel et al. in preparation --- see poster 9 in
the back
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Summary

• Water fountain pre-planetary nebula are likely
  keys to understanding the transition to
  asymmetric PN
• Measuring the proper motions and determining the
  3D velocities help to understand the kinematics
  and dynamics of the fast jet
• Optical lobes, when present, appear to co-exist
  with the water maser emission
• Dynamic ages of the water fountain are quite
  short 100 yr
• Astrometric VLBA observations can also be used
  to determine the trigonometric parallax and thus
  the distance to these water fountain PPN,
  obviously important to determine other physical
  parameters
• High angular resolution of the other water
  fountain candidates are necessary to compare with
  these presented here

June 19, 2007 APN IV