Molecular Line Survey of CRL 618 from 80 to 276 GHz and Complete Model

Abstract

We present the complete data set, model, and line identification of a survey of the emission from the C-rich proto–planetary nebula CRL 618 performed with the IRAM 30 m telescope in the frequency ranges 80.25–115.75 GHz, 131.25–179.25 GHz, and 204.25–275.250 GHz. A selection of lines from different species has been used in previous works to derive the structure of the source, its physical conditions, and the chemical abundances in the different gas regions. In this work, we have used this information to run a global simulation of the spectrum in order to check the consistency of the model and to ease the task of line identification. The total number of lines that have a correspondence in both data and model is ~3100, although quite often in this object many lines blend into complex features, so that the model, which takes into account line blending, is a key tool at this stage of the analysis. Of all the lines that we have been able to label, ~55% of them belong to the different forms of HC3N, and ~18% to HC5N. The density of remaining unidentified features above the 3 σ limit is only 1 per ~2.1 GHz (74 features), which is unprecedented in the analysis of this type of large millimeter-wave line surveys.