A HIGH RESOLUTION STUDY OF PLANETARY NEBULAE

Abstract

I present a high resolution study of 6 Planetary Nebulae observed in C-band and X-band. The C-band observations are available for two young Planetary Nebulae NGC 7027 and BD+303639 using high resolution A-array JVLA and eMERLIN observed in 2012 with archive data observed using A-array, B-array VLA and MERLIN in 1989 and 1995. Theses multi-epochs and arrays data are used to compute the expansion parallax distance to the two nebulae via two independent methods: from comparing the Half Width Half Maximum of radial profile plots in the different epochs and by producing a difference map from a model. These methods produce an averaged distance of 1058 +/- 242 pc (from radial profile plots) and 773 +/- 126 (from a model) for NGC 7027. The distance derived for BD+303639 is 1258 +/- 455 pc and 1178 +/- 368 pc from the radial profile plots and the model methods respectively. The time interval between observation is around 17 years dominated by the high resolution observations. The uncertainty in the distance arises mainly from measurements and model errors. The high resolution observation is capable of detecting a small changes resulting from velocities as low as 14 km/sec in the object at a distance of 1 kpc. The eMERLIN data are available only for NGC 7027. A future high resolution observation enhanced with compact configuration will improve the sensitivity to large scale structures and improve the expansion measurement producing more accurate distance for these rapidly expanding objects. The X-band radio observations exist for all six Planetary Nebulae: NGC 7027, BD+303639, NGC 2371, NGC 2392, NGC 4361, and LoTr5. These targets were observed by Chandra X-ray Observatory survey of PNe (Cycle 12) within 1.5 kpc. The last 4 targets show hard X-ray from the central star. The explanation for the hard X-ray emission has different mechanisms which also predicts a radio emission with variable strength. The radio observation for our sample will help to indicate the hard X-ray mechanism from the detected radio flux. One radio point source is detected in the core of LoTr5 which is known to have a companion. The emission from the companion is suggested to be the reason behind the detected hard X-ray. NGC 2371, NGC 2392, NGC 4361, and LoTr5 are objects observed in X-band as a part of the first comprehensive survey for detecting radio emission from the CSPNe which will provide evidence to reveal the possible mechanism for the detected hard X-ray from the CSPNe.