Observations of comet C/2020 F3 (NEOWISE) with IRAM telescopes^★,★★

¹ LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Université, Université Paris-Cité, 5 place Jules Janssen, 92195 Meudon, France
e-mail: nicolas.biver@obspm.fr
² IRAM, 300 rue de la Piscine, 38406 Saint-Martin-d’Hères, France
³ Univ. Paris-Est Créteil, Université Paris-Cité, LISA, CNRS, 94010 Créteil, France
⁴ Solar System Exploration Division, Astrochemistry Laboratory Code 691, NASA-GSFC, Greenbelt, MD 20771, USA
⁵ Department of Physics, Catholic University of America, Washington, DC 20064, USA

Received: 13 September 2022
Accepted: 4 November 2022

Abstract

We present the results of millimetre-wave spectroscopic and continuum observations of the comet C/2020 F3 (NEOWISE) undertaken with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m and the NOrthern Extended Millimeter Array (NOEMA) telescopes on 22, 25–27 July, and 7 August 2020. Production rates of HCN, HNC, CH₃OH CS, H₂CO, CH₃CN, H₂S, and CO were determined with upper limits on six other species. The comet shows abundances within the range observed for other comets. The CO abundance is low (3.2% relative to water), while H₂S is relatively abundant (1.1% relative to water). The H₂CO abundance shows a steep variation with heliocentric distance, possibly related to a distributed production from the dust or macro-molecular source. The CH₃OH and H₂S production rates show a slower decrease post-perihelion than water. There was no detection of the nucleus point source contribution based on the interferometric map of the continuum (implying a size of r < 4.7 km), but this yielded an estimate of the dust production rate, leading to a relatively low dust-to-gas ratio of 0.7 ± 0.3 on 22.4 July 2020.