Herschel-SPIRE FTS spectroscopy of the carbon-rich objects AFGL 2688, AFGL 618 and NGC 7027

TL;DR

This study uses Herschel-SPIRE FTS spectroscopy to analyze the far-infrared spectra of three carbon-rich evolved objects, revealing over 150 spectral lines, molecular detections, and physical conditions, including the first water detection in AFGL 2688.

Contribution

It provides detailed spectral data and initial models for these objects, including new molecular detections and insights into their physical conditions.

Findings

Detected over 150 lines per object

First water detection in AFGL 2688

Detected CH+ J=1-0 line in NGC 7027

Abstract

We present far-infrared and submillimetre spectra of three carbon-rich evolved objects, AFGL 2688, AFGL 618 and NGC 7027. The spectra were obtained with the SPIRE Fourier transform spectrometer on board the Herschel Space Observatory, and cover wavelengths from 195-670 um, a region of the electromagnetic spectrum hitherto difficult to study in detail. The far infrared spectra of these objects are rich and complex, and we measure over 150 lines in each object. Lines due to 18 different species are detected. We determine physical conditions from observations of the rotational lines of several molecules, and present initial large velocity gradient models for AFGL 618. We detect water in AFGL 2688 for the first time, and confirm its presence in AFGL 618 in both ortho and para forms. In addition, we report the detection of the J=1-0 line of CH+ in NGC 7027.