Herschel-SPIRE spectroscopy of the DR21 molecular cloud core

TL;DR

This study uses Herschel-SPIRE to analyze the DR21 molecular cloud core, detecting multiple molecular lines and revealing details about the temperature, density, and outflow-related gas components.

Contribution

First to present far-infrared spectra of DR21 with Herschel-SPIRE, identifying new molecular transitions and characterizing multiple gas components.

Findings

Warm gas with Tkin ~ 125 K and nH2 ~ 7 x 10^4 cm^-3

Detection of several new molecular lines

Identification of a cooler CO component at ~78 K

Abstract

We present far-infrared spectra and maps of the DR21 molecular cloud core between 196 and 671 microns, using the Herschel-SPIRE spectrometer. Nineteen molecular lines originating from CO, 13CO, HCO+ and H2O, plus lines of [N II] and [CI] were recorded, including several transitions not previously detected. The CO lines are excited in warm gas with Tkin ~ 125 K and nH2 ~ 7 x 10^4 cm-3, CO column density N(CO) ~ 3.5 x 10^18 cm^-2 and a filling factor of ~ 12%, and appear to trace gas associated with an outflow. The rotational temperature analysis incorporating observations from ground-based telescopes reveals an additional lower excitation CO compoment which has a temperature ~ 78 K and N(CO) ~ 4.5 x 10^21 cm^-2. Astronomy & Astrophysics HERSCHEL special Issue, in press.