Detection of OH 18-cm Emission from Comet C/2020 F3 NEOWISE using the Arecibo Telescope

TL;DR

This paper reports the first detection of OH 18-cm emission from comet C/2020 F3 NEOWISE using the Arecibo Telescope, providing measurements of OH column density and production rate, and discussing quenching effects.

Contribution

First detection of OH 18-cm emission from comet NEOWISE with Arecibo, including derived OH production rate and analysis of quenching effects.

Findings

OH emission detected at 1667 and 1665 MHz lines.

Derived OH production rate is approximately 3.6×10^{28} s^{-1}.

Observed OH production rate is lower than optical estimates, likely due to quenching.

Abstract

We report the detection of emission from the OH 18 cm $\Lambda$-doublet transitions toward Comet C/2020 F3 NEOWISE using the Arecibo Telescope. The antenna temperatures are 113$\pm$3 mK for the 1667 MHz line and 57$\pm$3 mK for the 1665 MHz line. The beam averaged OH column density (centered on the comet nucleus) derived from the 1667 transition is $N_{OH}$=1.11$\pm0.06\times10^{13}$ cm$^{-2}$. We implemented the Haser model to derive an OH production rate. The estimated OH production rate using the 1667 MHz transition is Q$_{OH}$=3.6$\pm0.6\times10^{28}$ s$^{-1}$, a factor of 2.4 lower than optically derived values for the same observing day, the difference of which is likely explained by quenching.