Molecular-line observations of the bipolar planetary nebula (PN) M2-48 have been conducted using the Sub-Millimeter Telescope and the 12 m antenna of the Arizona Radio Observatory at 1, 2, and 3 mm. M2-48 is estimated to be ∼4800 yr old, midway through the PN evolutionary track. SiO and SO2were detected in this source - the first identification of either molecule in a PN. CN, HCN, HNC, CS, SO, HCO+, N2H+, and several 13C isotopologues such as 13CN, H13CN, and H13CO+were also observed toward this object. A radiative transfer analysis of multiple SiO transitions indicates a gas kinetic temperature of TK∼ 55 K and a density of n(H2) ∼ 9 × 105cm-3in M2-48, in agreement with previous CS and CO modeling. After CO, CN, and SO were found to be the most prevalent molecules in this nebula, with fractional abundances, relative to H2, of f ∼ 3.8 × 10-7and 2.4 × 10-7, respectively. SO2and HCN are also abundant, with f ∼ 1.2 × 10-7, indicating an [SO]/[SO2] ratio of ∼2. Relatively high ion abundances were measured in M2-48 as well, with f ∼ 10-7for both HCO+and N2H+. An [HCN]/[HNC] ratio of ∼2 was determined, as typically observed in other PNe, independent of age. The high abundances of SO and SO2, along with the presence of SiO with f ∼ 2.9 × 10-8, suggest O/C > 1 in this source; furthermore, the prevalence of CN and N2H+indicates nitrogen enrichment. The 12C/13C ratio of ∼3 in the nebula was also established. These factors indicate hot-bottom burning occurred in the progenitor star of M2-48, suggesting an initial mass > 4 M⊙.
- ISM: molecules
- nuclear reactions, nucleosynthesis, abundances
- planetary nebulae: individual (M2-48)
- radio lines: ISM
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science