Mch. Wright et al., Mosaicked images and spectra of J=1 -> 0 HCN and HCO+ emission from comet Hale-Bopp (1995 O1), ASTRONOM J, 116(6), 1998, pp. 3018-3028
We used the BIMA array to map comet Hale-Bopp (1995 O1) in HCN and HCO+ emi
ssion at 89 GHz with 10 " angular resolution. The mosaicked images with sev
en pointing centers were combined with single-dish data to form completely
sampled images of a region similar to 4' in diameter. The HCN image is roug
hly compatible with a Haser model in which most of the HCN comes from the n
ucleus. However, clear deviations from circular symmetry are present, and r
oughly 20% of the HCN does not appear to come from the nuclear source. Freq
uently, the HCN has an asymmetric, double-peaked profile. The double peak i
s expected from the Haser model, and the asymmetry observed on April 3 coul
d come from an increased gas production toward the Sun and facing the obser
ver. The abundance of HCN relative to H2O is similar to 0.3%. The HCO+, in
contrast, is smooth, almost completely resolved in the interferometer obser
vations, and offset toward the ion tail by about 1'. This behavior is compa
tible with expectations from a simple scaling of previous work.