Faraday rotation in the tail of the planetary nebula DeHt 5.
RANSOM R.R., KOTHES R., WOLLEBEN M. and LANDECKER T.L.
Abstract (from CDS):
We present 1420 MHz polarization images of a 5°x5° region around the planetary nebula (PN) DeHt 5. The images reveal narrow Faraday-rotation structures on the visible disk of DeHt 5, as well as two wider, tail-like, structures "behind" DeHt 5. Though DeHt 5 is an old PN known to be interacting with the interstellar medium (ISM), a tail has not previously been identified for this object. The innermost tail is ∼3 pc long and runs away from the northeast edge of DeHt 5 in a direction roughly opposite that of the sky-projected space velocity of the white dwarf central star, WD 2218+706. We believe this tail to be the signature of ionized material ram-pressure stripped and deposited downstream during a >74,000 yr interaction between DeHt 5 and the ISM. We estimate the rotation measure (RM) through the inner tail to be -15±5 rad/m2, and, using a realistic estimate for the line-of-sight component of the ISM magnetic field around DeHt 5, derive an electron density in the inner tail of ne= 3.6±1.8/cm3. Assuming the material is fully ionized, we estimate a total mass in the inner tail of 0.68±0.33 M☉ and predict that 0.49±0.33 M☉ was added during the PN-ISM interaction. The outermost tail consists of a series of three roughly circular components, which have a collective length of ∼11.0 pc. This tail is less conspicuous than the inner tail and may be the signature of the earlier interaction between the WD 2218+706 asymptotic giant branch (AGB) progenitor and the ISM. The results for the inner and outer tails are consistent with hydrodynamic simulations and may have implications for the PN missing-mass problem as well as for models which describe the impact of the deaths of intermediate-mass stars on the ISM.