Examination of Fragment Species in the Comae of Several Comets Using an Integral Field Unit Spectrograph

Abstract

Spectra of the comae of four comets were obtained with an integral field unit spectrograph on the Harlan J. Smith Telescope at McDonald Observatory. The passband of the spectrograph permitted the observation of C2, C3, CH, CN, and NH2 transitions for these comets. The classical Haser model was used to derive production rates for each observed species. The production rates obtained for the comets were also used to obtain mixing ratios relative to CN. The relative abundances with respect to CN obtained for these comets vary greatly, but are largely consistent with ranges established from prior comet chemistry surveys. The notable exception is 168P/Hergenrother, which the results suggest is extremely depleted in volatiles, even with respect to many other comets designated as volatile depleted in prior surveys. The results for comet Hergenrother add to a small, but growing, body of data suggesting that there may be a subgroup of carbon-chain-depleted Jupiter-family comets that are also depleted in ammonia.

Photodissociation of dicarbon: How nature breaks an unusual multiple bond

“…This results in a lifetime of 1.2 × 10 5 s at 1 AU, which is about 0.7 of that determined above. Recently, Pierce and Cochran (61) reported the spatial analysis of four comets using an integral field spectrograph. They adopted a scale length for C2 of 120,000 km, with an outflow velocity at 1 AU of 0.85 km•s −1 .…”

FeI and NiI in cometary atmospheres

“…Since there is evidence that some carbon-chain JFCs are also depleted in NH2 and NH (Fink 2009;Cochran et al 2012;Pierce & Cochran 2021), we looked for a correlation between the NiI/FeI and NH/CN abundance ratios measured in our spectra (Table A.1). Figure 5 shows this correlation, the comets with the smallest NH/CN ratios showing the highest NiI/FeI ratios.…”

“…While dominated by JFCs, the correlation also involves C/2009 P1 (Garradd), which has low NH/CN and high NiI/FeI ratios. It should be noted that Pierce & Cochran (2021)…”