2026/07/28 by Hao-Min Sun, Zhuang Zhang, Jun-Yang Liu +2
#astro-ph.GA #astro-ph.SR
The identification of the 21 μm feature in some protoplanetary nebulae remains a longstanding puzzle, whose interpretation requires characterization of the molecular gas environments of associated sources. Here, we present high-resolution interferometric observations from the Northern Extended Millimeter Array toward the 21 μm protoplanetary nebula IRAS 06530-0213. Multiple molecular transitions of HC3N, C4H, and SiC2 are detected and spatially resolved. We analyze these spectral lines alongside previously reported CO and 13CO emission toward this source. Differing from the extended barrel-like molecular structure traced by CO and 13CO, HC3N and C4H are predominantly concentrated in the inner low-latitude equatorial zones. Reproducing the observed morphology requires HC3N to possess a more inwardly concentrated abundance distribution compared with CO and 13CO, implying that the inner equatorial regions provide favorable conditions for carbon-chain chemistry.