New Detections of HNC in Planetary Nebulae: Evolution of the [Hcn]/[Hnc] Ratio

Abstract

New detections of HNC have been made toward 11 planetary nebulae (PNe), including K4-47, K3-58, K3-17, M3-28, and M4-14

New Identifications of the CCH Radical in Planetary Nebulae: A Connection to C60?

“…LSR velocities reside in the range of −2 to −8.5 km s −1 -consistent with those measured for HCN, HCO + , and HNC (Schmidt & Ziurys 2016, 2017. The narrower line widths of ∼5-7 km s −1 for the 3 mm transitions, as opposed to near 40 km s −1 for the N = 3 → 2 lines at 1 mm, mimic those observed in the HCN and HCO + .…”

“…For K3-45 and M3-28, the red-and blueshifted velocity components of the N = 3 → 2 spin-rotation doublets were fit individually. As shown in the table, the line intensities fall into the range of ∼2-12 mK, while the line widths and LSR velocities are comparable to those seen in HCN, HNC, and HCO + (see Schmidt & Ziurys 2016, 2017. The individual nebulae are briefly described below.…”

“…As aforementioned, 11 of these sources were previously detected in HCN by Schmidt & Ziurys (2016) and HNC by Schmidt & Ziurys (2017). All but two of these sources (K3-45 and NGC 6772) were also detected in at least one transition of HCO + .…”

“…The Helix Nebula, for example, has been found to contain an array of molecules, including HCN, HNC, HCO + , H 2 CO, c-C 3 H 2 , CCH, and CN (Bachiller et al 1997;Tenenbaum et al 2009). Many of these species have been found to be well-distributed throughout the nebula Zeigler et al 2013;Schmidt & Ziurys 2017). Such results are particularly surprising, given that the Helix Nebula is one of the oldest PNe known, with an age of ∼10,000 years.…”

“…Very recent work by Schmidt & Ziurys (2016, 2017 has expanded the number of nebulae detected in HCN, HCO + , and HNC by over a factor of 2, suggesting that these molecules are commonly present in PNe. Furthermore, the sample of 11-13 PNe in which these molecules have been found evenly spans a range of kinematic ages (determined from the intrinsic radius and expansion velocity of the nebula), from ∼900 years to ∼11,000 years, as well as morphologies.…”