H91$\alpha$ Radio Recombination Line and 3.5 cm Continuum Observations of the Planetary Nebula NGC 3242

TL;DR

This study uses high-sensitivity radio observations to analyze the electron temperature, spatial distribution, and velocity structure of the planetary nebula NGC 3242, confirming consistency with optical data and ruling out spinning dust emission.

Contribution

First high-sensitivity radio observations of NGC 3242's H91α line and continuum, demonstrating consistency with optical measurements and clarifying emission mechanisms.

Findings

Electron temperature matches optical estimates within 10%.

Radio and optical emissions have similar spatial distribution.

Spinning dust emission is negligible at this wavelength.

Abstract

We present high sensitivity H91$\alpha$ and 3.5 cm radio continuum observations toward the planetary nebula NGC 3242. The electron temperature determined assuming local thermodynamic equilibrium is consistent within $\sim$10% with that derived from optical lines and the Balmer discontinuity. The line emission and the continuum emission have very similar spatial distribution, suggesting that at this wavelength there is no other continuum process present in a significant manner. In particular, we conclude that emission from spinning dust is not important at this wavelength. In this radio recombination line the nebula presents a radial velocity structure consistent with that obtained from observations of optical lines.