Tracing the atomic nitrogen abundance in star-forming regions with ammonia deuteration

Abstract

Partitioning of elemental nitrogen in star-forming regions is not well constrained. Most nitrogen is expected to be partitioned among atomic nitrogen, molecular nitrogen (N2), and icy N-bearing molecules, such as ammonia (NH3) and N2. Atomic nitrogen is not directly observable in the cold gas. In this paper, we propose an indirect way to constrain the amount of atomic nitrogen in the cold gas of star-forming clouds, via deuteration in ammonia ice, the [ND2H/NH2D]/[NH2D/NH3] ratio. Using gas-ice astrochemical simulations, we show that if atomic nitrogen remains as the primary reservoir of nitrogen during cold ice formation stages, the [ND2H/NH2D]/[NH2D/NH3] ratio is close to the statistical value of 1/3 and lower than unity, whereas if atomic nitrogen is largely converted into N-bearing molecules, the ratio should be larger than unity. Observability of ammonia isotopologues in the inner hot regions around low-mass protostars, where ammonia ice has sublimated, is also discussed. We conclude that the [ND2H/NH2D]/[NH2D/NH3] ratio can be quantified using a combination of VLA and ALMA observations with reasonable integration times, at least toward IRAS 16293-2422 where high molecular column densities are expected.

arXiv commentAccepted for publication in MNRAS, 12 pages, 9 figures, 1 Table

References in corpus (68)

• Astrophysics Source Code Library
• Observations of the Icy Universe
• Cold Dark Clouds: The Initial Conditions for Star Formation
• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• The Spitzer ice legacy: Ice evolution from cores to protostars
• The photodissociation and chemistry of CO isotopologues: applications to interstellar clouds and circumstellar disks
• Photodissociation and photoionisation of atoms and molecules of astrophysical interest
• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• On the Formation of CO2 and Other Interstellar Ices
• Simulation of the Formation and Morphology of Ice Mantles on Interstellar Grains
• Astrometry of Water Maser Sources in Nearby Molecular Clouds with VERA - II. SVS 13 in NGC 1333
• Binding energies: new values and impact on the efficiency of chemical desorption
• A cosmic abundance standard: chemical homogeneity of the solar neighbourhood and the ISM dust-phase composition
• Molecular Cloud Formation Behind Shock Waves
• Near-arcsecond resolution observations of the hot corino of the solar type protostar IRAS 16293-2422
• Mapping ices in protostellar environments on 1000 AU scales: Methanol-rich ice in the envelope of Serpens SMM 4
• Testing grain surface chemistry : a survey of deuterated formaldehyde and methanol in low-mass Class 0 protostars
• CO ice photodesorption: A wavelength-dependent study
• A Unified Monte Carlo Treatment of Gas-Grain Chemistry for Large Reaction Networks. II. A Multiphase Gas-Surface-Layered Bulk Model
• A study of deuterated water in the low-mass protostar IRAS16293-2422
• An interferometric study of the low-mass protostar IRAS 16293-2422: small scale organic chemistry
• Isotopic fractionation of carbon, deuterium and nitrogen : a full chemical study
• From Prestellar to Protostellar Cores II. Time Dependence and Deuterium Fractionation
• Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores
• The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar medium
• The interstellar gas-phase chemistry of HCN and HNC
• Interstellar deuterated ammonia: From NH3 to ND3
• Thermal desorption characteristics of CO, O2 and CO2 on non-porous water, crystalline water and silicate surfaces at sub-monolayer and multilayer coverages
• Interstellar chemistry of nitrogen hydrides in dark clouds
• Spatial mapping of ices in the Oph-F core: A direct measurement of CO depletion and the formation of CO2
• Nitrogen chemistry and depletion in starless cores
• Atomic Deuterium/Hydrogen in the Galaxy
• Gas-grain chemistry in cold interstellar cloud cores with a microscopic Monte Carlo approach to surface chemistry
• CO and N${}_2$ desorption energies from water ice
• Water Formation through a Quantum Tunneling Surface Reaction, OH + H2, at 10 K
• Arcsecond resolution images of the chemical structure of the low-mass protostar IRAS 16293-2422
• Simultaneous Hydrogenation and UV-photolysis Experiments of NO in CO-rich Interstellar Ice Analogues; linking HNCO, OCN-, NH2CHO and NH2OH
• Indirect ultraviolet photodesorption from CO:N2 binary ices - an efficient grain-gas process
• Photodissociation of interstellar N2
• On the robustness of the ammonia thermometer
• Formaldehyde and methanol deuteration in protostars: fossiles from a past fast high density pre-collapse phase
• Low Temperature Surface Formation of NH3 and HNCO: hydrogenation of nitrogen atoms in CO-rich interstellar ice analogues
• Elemental nitrogen partitioning in dense interstellar clouds
• Nitrogen superfractionation in dense cloud cores
• Water deuteration and ortho-to-para nuclear spin ratio of H2 in molecular clouds formed via the accumulation of HI gas
• Reconstructing the history of water ice formation from HDO/H2O and D2O/HDO ratios in protostellar cores
• High Resolution 4.7 um Keck/NIRSPEC Spectra of Protostars. II: Detection of the 13CO Isotope in Icy Grain Mantles
• Direct measurement of desorption and diffusion energies of O and N atoms physisorbed on amorphous surfaces
• Interstellar ices as witnesses of star formation: selective deuteration of water and organic molecules unveiled
• HD depletion in starless cores
• Deuterated Ammonia in Galactic Protostellar Cores
• Warm water deuterium fractionation in IRAS 16293-2422 - The high-resolution ALMA and SMA view
• Sticking of molecules on non-porous amorphous water ice
• Interstellar Simulations Using A Unified Microscopic-Macroscopic Monte Carlo Model with a full Gas-Grain Network including Bulk Diffusion in Ice Mantles
• Deuteration of ammonia in the starless core Ophiuchus/H-MM1
• Kinematics of the Ammonia Disk around the Protostar NGC 1333 IRAS 4A2
• Constraining the physical structure of the inner few 100 AU scales of deeply embedded low-mass protostars
• High D${}_2$O/HDO ratio in the inner regions of the low-mass protostar NGC1333 IRAS2A
• The Effects of Grain Size and Temperature Distributions on the Formation of Interstellar Ice Mantles
• Photodesorption of H2O, HDO, and D2O ice and its impact on fractionation
• UV photoprocessing of NH3 ice: photon-induced desorption mechanisms
• Beyond the pseudo-time-dependent approach: chemical models of dense core precursors
• Deuterium enrichment of ammonia produced by surface N+H/D addition reactions at low temperature
• Ammonia Imaging of the Disks in the NGC 1333 IRAS 4A Protobinary System
• Chemical fractionation of deuterium in the protosolar nebula
• Very Large Array Ammonia Observations of the HH 111/HH 121 Protostellar System: a Detection of a New Source With a Peculiar Chemistry
• Review of important reactions for the nitrogen chemistry in the interstellar medium

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• The first interferometric measurements of NH${}_2$D/NH${}_3$ ratio in hot corinos
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