Spectral Survey of the Star Formation Region DR21OH in the 4-mm Wavelength Range

This is the authors' abstract. We don't add key points for this paper.

The results of a spectral survey of the region of massive star formation DR21OH in the 4-mm wavelength range are presented. Sixty-nine molecules and their isotopologues have been detected, ranging from simple diatomic or triatomic species such as SO, SiO and CCH, to complex organic molecules such as CH3OCHO or CH3OCH3. The obtained results qualitatively repeat the results of the survey of the same source at 3 mm. The inventories of molecules found at 3 and 4 mm overlap to a great extent. However, at 4 mm we found a number of species that have no allowed transitions in the 3-mm wavelength range, e.g., DCN, DNC, or SO+. The bulk of the molecules detected at 4 mm are those that are common for dense cores, e.g., HC3N or CH3CCH, but some of the detected species are typical for hot cores. The latter include complex organic molecules CH3OCHO, CH3CH2OH, CH3OCH3, etc. However, the detected emission of these molecules probably arises in a gas heated to 30 K only. Nine molecules, including complex species CH3C3N, CH3CH2CN, CH3COCH3, were found by spectral line stacking. This demonstrates the prospects of the method in the study of molecular clouds.