Asymmetric Planetary Nebulae IV

La Palma, Canary Islands

Water Fountains in Pre-Planetary Nebulae

Mark Claussen, NRAOJune 19, 2007

Hancock, New HampshireVLBA Antenna

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

June 19, 2007 APN IV

Water Masers and High Angular Resolution

• 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 as or better, depending on tropospheric correction

June 19, 2007 APN IV

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

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

IRAS 16342-3814Estimated Distance of 2 kpcBipolar protoplanetary nebula“Water Fountain” NebulaClaussen, Sahai, and Morris

1000 AU

IRAS 16342-3814Estimated Distance of 2 kpcBipolar protoplanetary nebula“Water Fountain” Nebula

1000 AU

2000 AU

Where the water masers are in IRAS16342

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

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.

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.

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).

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.

VLBA Observations of water masers in the water fountain OH12.8-0.9 (from Boboltz & Marvel, in press)

Water Masers in OH12.8-0.9 (IRAS 18139-1816)

Summary of Four Water Fountain Sources’ Properties

June 19, 2007 APN IV

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

IRAS19190+1102 Water Masers (the fifth high resolution water fountain)

Creel et al. in preparation --- see poster #9 in the back

VLSR = -20 --- 10 km/s

VLSR = 38 --- 80 km/s

Summary

June 19, 2007 APN IV

• 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