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Water Fountains in Pre-Planetary Nebulae

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. Water Fountain Pre-Planetary Nebulae.

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Water Fountains in Pre-Planetary Nebulae

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  1. 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

  2. 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 Deacon’s 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 .

  3. June 19, 2007 APN IV

  4. Water Masers and High Angular Resolution • Water maser characteristics: • Excitation temperature > 400 K • Molecular hydrogen densities > 109 cm-3 (for collisional excitation) • And, need velocity coherence along the maser • VLBA has superb angular resolution which allows proper motion studies ( < 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

  5. 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

  6. IRAS 16342-3814 Estimated Distance of 2 kpc Bipolar protoplanetary nebula “Water Fountain” Nebula Claussen, Sahai, and Morris 1000 AU

  7. IRAS 16342-3814 Estimated Distance of 2 kpc Bipolar protoplanetary nebula “Water Fountain” Nebula 1000 AU

  8. Where the water masers are in IRAS16342 2000 AU

  9. 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

  10. 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.

  11. 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.

  12. HST images of IRAS19134+2131. The solid line shows the position angle of the projected flow expansion vector derived from the water masers; it’s length of 139 mas is equal to the separation of the red and blue-shifted maser features (Imai, Sahai, Morris, in the press).

  13. 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.

  14. 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)

  15. Summary of Four Water Fountain Sources’ Properties ** measured from trigonometric parallax of water masers June 19, 2007 APN IV

  16. IRAS19190+1102 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

  17. 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

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