Millimeter-wave observations of CO in planetary nebulae

We present NRAO 12 m observations of CO (J = 1-0 and J = 2-1) in six planetary nebulae, including the first confirmed detection of a molecular outflow in K3-35 and the first observations of J = 1-0 emission from NGC 2440. The J = 2-1 spectrum toward K3-35 shows a strong peak at ∼10 km s^-1 (V_1sr) and a ∼40 km s^-1 wide, lower excitation, high-velocity component. The strong peak is narrow (<5 km s^-1) and is probably associated with a Galactic molecular cloud; the high-velocity emission feature indicates an outflow velocity of about 17 km s^-1. The CO lines toward NGC 2440 are broad and double peaked, and indicate an expansion velocity of ∼29 km s^-1. The emission lines from IC 5117 are bright and "two-horned," and suggest an expansion velocity of 17 km s^-1. Observations toward AFGL 915 show narrow and single-peaked emission lines that have ∼20 km s^-1 wide wings. The 115 GHz observation toward IC 418 shows a broad emission line, which we believe is the H38α recombination line. To confirm this, we also observed the H38α recombination line at 106.7 GHz. A comparison of the two lines suggests that there is no significant molecular emission at 115 GHz. We estimate the contribution from the H38α recombination line in each of our sources, to avoid overestimating the molecular emission. Using estimates of the distance (from the literature), we calculate or obtain limits to the total amount of molecular gas in our sources.