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Near Infrared Observation of comet C/2022 E3 (ZTF) using iSHELL at NASA-IRTF.

Presentation #322.09 in the session Comets (Poster)

Published onOct 23, 2023
Near Infrared Observation of comet C/2022 E3 (ZTF) using iSHELL at NASA-IRTF.

Comets are volatile-rich small bodies that are among the most primitive remnants of early solar system formation. The chemical composition of volatile gases in the comae as a reflection of ice abundances in the nuclei of comets can provide valuable insights into the early solar system’s initial conditions and subsequent evolution. Comets are often regarded as “fossils” of solar system formation, with the native composition of their ices reflecting formation conditions (e.g., composition, temperature, radiation field; Mumma et al. 2011; Saki et al. 2020).

C/2022 E3 (ZTF) (hereafter E3) is a long period, Oort cloud comet that we observed in the near-infrared region utilizing the ~1-5.3 μm powerful high-resolution (λ/Δλ ~ 42,000) immersion-grating echelle spectrograph iSHELL at NASA Infrared Telescope Facility (IRTF) (Rayner et al. 2022). This allowed us to characterize the volatile composition of E3 via analysis of coma fluorescence emissions.

We report results from E3 spectra on two post-perihelion UT dates, 2023 January 20 and 22. Three iSHELL settings (Lcustom, Lp1, and M2) sampled 8 trace molecules (C2H6, CH4, CH3OH, OCS, C2H2, HCN, CO, H2CO) plus H2O. Lcustom included multiple strong water lines that were used to establish the rotational temperature of the coma. The large geocentric velocity of E3 (~ -45km/s) Doppler-shifted the cometary CH4 and CO lines from their corresponding (opaque) telluric absorptions, into regions of favorable atmospheric transmittance.

In this work we will present production rates (mol/s), the molecular mixing ratios with respect to both H2O and C2H6 and discuss their significance. Results from Keck 2/NIRSPEC observations in two L-band settings (KL1 and KL2) provide complementary measurements of E3 on two UT dates (DiSanti et al., this conference). Although separated by several hours, one of these dates (UT January 20) features both iSHELL and NIRSPEC observations.

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