The physics and kinematics of the evolved, interacting planetary nebula PN G342.0-01.7

TL;DR

This study investigates the physical and kinematic properties of the old, interacting planetary nebula PN G342.0-01.7, revealing its evolutionary stage, interaction with the interstellar medium, and challenging assumptions based on excitation class.

Contribution

The paper provides a detailed analysis of an unstudied planetary nebula, including spectroscopic data, photoionisation modeling, and insights into its interaction with the interstellar medium, highlighting limitations of excitation-based classification.

Findings

PN G342.0-01.7 is a low-excitation, old planetary nebula with low surface brightness.

It shows evidence of interaction with the interstellar medium through slow shocks.

The effective temperature derived is higher than excitation class suggests, indicating classification challenges.

Abstract

Here we aim to study the physical and kinematical characteristics of the unstudied old planetary nebula (PN) PN G342.0-01.7, which shows evidence of interaction with its surrounding interstellar medium. We used Integral Field Spectra from the Wide Field Spectrograph on the ANU 2.3 m telescope to provide spectroscopy across the whole object covering the spectral range 3400-7000 {\AA}. We formed narrow-band images to investigate the excitation structure. The spectral analysis shows that the object is a distant Peimbert Type I PN of low excitation, formally of excitation class of 0.5. The low electron density, high dynamical age, and low surface brightness of the object confirm that it is observed fairly late in its evolution. It shows clear evidence for dredge-up of CN-processed material characteristic of its class. In addition, the low peculiar velocity of 7 km s$^{-1}$ shows it to be a member of the young disk component of our Galaxy. We built a self-consistent photoionisation model for the PNe matching the observed spectrum, the H$\beta$ luminosity, and the diameter. On the basis of this we derive an effective temperature $\log T_{\rm eff} \sim 5.05$ and luminosity $1.85 < \log L < 2.25$. The temperature is much higher than might have been expected using the excitation class, proving that this can be misleading in classifying evolved PNe. PN G342.0-01.7 is in interaction with its surrounding interstellar medium through which the object is moving in the south-west direction. This interaction drives a slow shock into the outer PN ejecta. A shock model suggests that it only accounts for about 10\% of the total luminosity, but has an important effect on the global spectrum of the PN.