ATLASGAL -- selected massive clumps in the inner Galaxy. IX. Deuteration of ammonia

Abstract

Deuteration has been used as a tracer of the evolutionary phases of low- and high-mass star formation. The APEX Telescope Large Area Survey (ATLASGAL) provides an important repository for a detailed statistical study of massive star-forming clumps in the inner Galactic disc at different evolutionary phases. We study the amount of deuteration using NH2D in a representative sample of high-mass clumps discovered by the ATLASGAL survey covering various evolutionary phases of massive star formation. Unbiased spectral line surveys at 3 mm were thus conducted towards ATLASGAL clumps between 85 and 93 GHz with the Mopra telescope and from 84 to 115 GHz using the IRAM 30m telescope. A subsample was followed up in the NH2D transition at 74 GHz with the IRAM 30m telescope. We determined the deuterium fractionation from the column density ratio of NH2D and NH3 and measured the NH2D excitation temperature for the first time from the simultaneous modelling of the 74 and 110 GHz line using MCWeeds. We find a large range of the NH2D to NH3 column density ratio up to 1.6+/-0.7 indicating a high degree of NH3 deuteration in a subsample of the clumps. Our analysis yields a clear difference between NH3 and NH2D rotational temperatures for a fraction of the sources. We therefore advocate observation of the NH2D transitions at 74 and 110 GHz simultaneously to determine the NH2D temperature directly. We determine a median ortho-to-para column density ratio of 3.7+/-1.2. The high detection rate of NH2D confirms a high deuteration previously found in massive star-forming clumps. Using the excitation temperature of NH2D instead of NH3 is needed to avoid an overestimation of deuteration. We measure a higher detection rate of NH2D in sources at early evolutionary stages. The deuterium fractionation shows no correlation with evolutionary tracers such as the NH3 (1,1) line width, or rotational temperature.

References in corpus (14)

• Cold Dark Clouds: The Initial Conditions for Star Formation
• ATLASGAL --- properties of a complete sample of Galactic clumps
• Observing the gas temperature drop in the high-density nucleus of L 1544
• ATLASGAL --- towards a complete sample of massive star forming clumps
• The N2D+/N2H+ ratio as an evolutionary tracer of Class 0 protostars
• ATLASGAL-selected massive clumps in the inner Galaxy: I. CO depletion and isotopic ratios
• ATLASGAL - Kinematic distances and the dense gas mass distribution of the inner Galaxy
• ATLASGAL-selected massive clumps in the inner Galaxy III. Dust Continuum Characterization of an Evolutionary Sample
• Benchmarking spin-state chemistry in starless core models
• Probing the initial conditions of High Mass Star formation -- I. Deuteration and depletion in high mass pre/protocluster clumps
• Deuteration and evolution in the massive star formation process: the role of surface chemistry
• Massive and low-mass protostars in massive "starless" cores
• ATLASGAL --- Molecular fingerprints of a sample of massive star forming clumps
• Collisional excitation of singly deuterated ammonia NH${}_2$D by H${}_2$

Cited by in corpus (11)

• The Gaia-ESO Survey: Target selection of open cluster stars
• TRAO Survey of the nearby filamentary molecular clouds, the universal nursery of stars (TRAO FUNS). II. Filaments and Dense cores in IC 5146
• Deuterated ammonia in Galactic massive star-forming regions
• Variations of the HCO${}^{+}$, HCN, HNC, N${}_2$H${}^{+}$ and NH${}_3$ deuterium fractionation in high-mass star-forming regions
• A Systematic Observational Study on Galactic Interstellar Ratio 18O/17O. II. C18O and C17O J=2-1 Data Analysis
• Molecular deuterations in massive Starless Clump Candidates
• Spatial distribution of NH2D in massive star-forming regions
• CH${}_3$OH as a User-Friendly Density Probe: Calibration and Beyond
• First detection of deuterated methylidyne (CD) in the interstellar medium
• Cl+ and HCl+ in Reaction with H2 and Isotopologues: A Glance into H Abstraction and Indirect Exchange at Astrophysical Conditions
• An 18 - 25 GHz spectroscopic survey of southern hemisphere dense cores