ALMA and GMRT Studies of Dust Continuum Emission and Spectral Lines Toward Oort Cloud Comet C/2022 E3 (ZTF)

Abstract

The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules arise mainly in three ways: (i) the outgassing from the nucleus, (ii) the photochemical process, and (iii) the sublimation of icy grains from the nucleus. In this paper, we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3 (ZTF) using the Giant Metrewave Radio Telescope (GMRT) band L and the Atacama Large Millimeter/Submillimeter Array (ALMA) band 6. We do not detect continuum emissions and an emission line of atomic hydrogen (HI) at rest frequency 1420 MHz from this comet using the GMRT. Based on ALMA observations, we detect the dust continuum emission and rotational emission lines of methanol (CH${}_3$OH) from comet C/2022 E3 (ZTF). From the dust continuum emission, the activity of dust production (Af$\rho$) of comet ZTF is 2280$\pm$50 cm. Based on LTE spectral modelling, the column density and excitation temperature of CH${}_3$OH towards C/2022 E3 (ZTF) are (4.50$\pm$0.25)$\times$10${}^{14}$ cm${}^{-2}$ and 70$\pm$3 K. The integrated emission maps show that CH${}_3$OH was emitted from the coma region of the comet. The production rate of CH${}_3$OH towards C/2022 E3 (ZTF) is (7.32$\pm$0.64)$\times$10${}^{26}$ molecules s${}^{-1}$. The fractional abundance of CH${}_3$OH with respect to H${}_2$O in the coma of the comet is 1.52%. We also compare our derived abundance of CH${}_3$OH with the existence modelled value, and we see the observed and modelled values are nearly similar. We claim that CH${}_3$OH is formed via the subsequential hydrogenation of formaldehyde (H${}_2$CO) on the grain surface of comet C/2022 E3 (ZTF).

Published in Research in Astronomy and Astrophysics (RAA)

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