Volatile Abundances, Extended Coma Sources, and Nucleus Ice Associations in Comet C/2014 Q2 (Lovejoy)

Abstract High-resolution infrared spectra of comet C/2014 Q2 Lovejoy were acquired with NIRSPEC at the W. M. Keck Observatory on two post-perihelion dates (UT 2015 February 2 and 3). H 2 O was measured simultaneously with CO, CH 3 OH, H 2 CO, CH 4 , C 2 H 6 , C 2 H 4 , C 2 H 2 , HCN, and NH 3 on both dates, and rotational temperatures, production rates, relative abundances, H 2 O ortho-to-para ratios, and spatial distributions in the coma were determined. The first detection of C 2 H 4 in a comet from ground-based observations is reported. Abundances relative to H 2 O for all species were found to be in the typical range compared with values for other comets in the overall population to date. There is evidence of variability in rotational temperatures and production rates on timescales that are small compared with the rotational period of the comet. Spatial distributions of volatiles in the coma suggest complex outgassing behavior. CH 3 OH, HCN, C 2 H 6 , and CH 4 spatial distributions in the coma are consistent with direct release from associated ices in the nucleus and are peaked in a more sunward direction compared with co-measured dust. H 2 O spatial profiles are clearly distinct from these other four species, likely due to a sizable coma contribution from icy grain sublimation. Spatial distributions for C 2 H 2 , H 2 CO, and NH 3 suggest substantial contributions from extended coma sources, providing further evidence for distinct origins and associations for these species in comets. CO shows a different spatial distribution compared with other volatiles, consistent with jet activity from discrete nucleus ice sources.