Reconstructing the history of water ice formation from HDO/H2O and D2O/HDO ratios in protostellar cores

Abstract

Recent interferometer observations have found that the D2O/HDO abundance ratio is higher than that of HDO/H2O by about one order of magnitude in the vicinity of low-mass protostar NGC 1333-IRAS 2A, where water ice has sublimated. Previous laboratory and theoretical studies show that the D2O/HDO ice ratio should be lower than the HDO/H2O ice ratio, if HDO and D2O ices are formed simultaneously with H2O ice. In this work, we propose that the observed feature, D2O/HDO > HDO/H2O, is a natural consequence of chemical evolution in the early cold stages of low-mass star formation: 1) majority of oxygen is locked up in water ice and other molecules in molecular clouds, where water deuteration is not efficient, and 2) water ice formation continues with much reduced efficiency in cold prestellar/protostellar cores, where deuteration processes are highly enhanced due to the drop of the ortho-para ratio of H2, the weaker UV radiation field, etc. Using a simple analytical model and gas-ice astrochemical simulations tracing the evolution from the formation of molecular clouds to protostellar cores, we show that the proposed scenario can quantitatively explain the observed HDO/H2O and D2O/HDO ratios. We also find that the majority of HDO and D2O ices are likely formed in cold prestellar/protostellar cores rather than in molecular clouds, where the majority of H2O ice is formed. This work demonstrates the power of the combination of the HDO/H2O and D2O/HDO ratios as a tool to reveal the past history of water ice formation in the early cold stages of star formation and when the enrichment of deuterium in the bulk of water occurred. Further observations are needed to explore if the relation, D2O/HDO > HDO/H2O, is common in low-mass protostellar sources.

Accepted for publication in A&A

References in corpus (14)

• Observations of the Icy Universe
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Laboratory evidence for efficient water formation in interstellar ices
• The importance of the ortho:para H2 ratio for the deuteration of molecules during pre-protostellar collapse
• Formation of hydrogen peroxide and water from the reaction of cold hydrogen atoms with solid oxygen at 10K
• Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores
• Spatial mapping of ices in the Oph-F core: A direct measurement of CO depletion and the formation of CO2
• Water Formation through a Quantum Tunneling Surface Reaction, OH + H2, at 10 K
• Water deuteration and ortho-to-para nuclear spin ratio of H2 in molecular clouds formed via the accumulation of HI gas
• Warm water deuterium fractionation in IRAS 16293-2422 - The high-resolution ALMA and SMA view
• High D${}_2$O/HDO ratio in the inner regions of the low-mass protostar NGC1333 IRAS2A
• Chemical modeling of water deuteration in IRAS16293-2422
• Thermal H/D exchange in polar ice - deuteron scrambling in space

Cited by in corpus (46)

• Astrochemistry During the Formation of Stars
• Astrochemistry and compositions of planetary systems
• The ALMA-PILS survey: Isotopic composition of oxygen-containing complex organic molecules toward IRAS 16293-2422B
• Elemental and molecular abundances in comet 67P/Churyumov-Gerasimenko
• Cometary Chemistry and the Origin of Icy Solar System Bodies, the view after Rosetta
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar medium
• CO destruction in protoplanetary disk midplanes: inside versus outside the CO snow surface
• Constraining Gas-Phase Carbon, Oxygen, and Nitrogen in the IM Lup Protoplanetary Disk
• The ALMA-PILS survey: Formaldehyde deuteration in warm gas on small scales toward IRAS 16293-2422 B
• Adsorption energies of carbon, nitrogen, and oxygen atoms on the low-temperature amorphous water ice: A systematic estimation from quantum chemistry calculations
• Complex organic molecules in low-mass protostars on Solar System scales -- II. Nitrogen-bearing species
• Water delivery from cores to disks: deuteration as a probe of the prestellar inheritance of H2O
• Volatile species in comet 67P/Churyumov-Gerasimenko -- investigating the link from the ISM to the terrestrial planets
• Why does ammonia not freeze out in the center of pre-stellar cores?
• High D/H ratios in water and alkanes in comet 67P/Churyumov-Gerasimenko measured with the Rosetta/ROSINA DFMS
• Prestellar grain-surface origins of deuterated methanol in comet 67P/Churyumov-Gerasimenko
• The detection of a hot molecular core in the extreme outer Galaxy
• ALMA observations of water deuteration: A physical diagnostic of the formation of protostars
• Diffusion activation energy and desorption activation energy for astrochemically relevant species on water ice show no clear relation
• ALMA observations of doubly deuterated water: Inheritance of water from the prestellar environment
• Multiple paths of deuterium fractionation in protoplanetary disks
• X-ray induced chemistry of water and related molecules in low-mass protostellar envelopes
• JWST detections of amorphous and crystalline HDO ice toward massive protostars
• Successive deuteration in low-mass star-forming regions: the case of D${}_2$-methanol (CHD${}_2$OH) in IRAS 16293-2422
• Methanol deuteration in high-mass protostars
• Chemical evolution during the formation of a protoplanetary disk
• Modeling chemistry during star formation: Water deuteration in dynamic star-forming regions
• A 3D physico-chemical model of a pre-stellar core. I. Environmental and structural impact on the distribution of CH${}_3$OH and $c$-C${}_3$H${}_2$
• Tracing the atomic nitrogen abundance in star-forming regions with ammonia deuteration
• The Molecular Composition of Shadowed Protosolar Disk Midplanes beyond the Water Snowline
• H${}_2$ ortho-para spin conversion on inhomogeneous grain surfaces
• A high HDO/H${}_2$O ratio in the Class I protostar L1551 IRS5
• Cold Deuterium Fractionation in the Nearest Planet-Forming Disk
• The Detection of Deuterated Water in the Large Magellanic Cloud with ALMA
• Carbon Isotope Fractionation of Complex Organic Molecules in Star-Forming Cores
• Pristine ices in a planet-forming disk revealed by heavy water
• The first interferometric measurements of NH${}_2$D/NH${}_3$ ratio in hot corinos
• Analysis of Low Excitation HDO Transitions Toward the High-Mass Star-forming Regions G34.26+0.15, W51e${}_1$/e${}_2$, and W49N
• Radiation-induced D/H Exchange Rate Constants in Aliphatics Embedded in Water Ice
• The hot corino-like chemistry of four FUor-like protostars
• Deuterium Chemistry in the Young Massive Protostellar Core NGC 2264 CMM3
• A Pathway for Collisional Planetesimal Growth in the Ice-Dominant Regions of Protoplanetary Disks
• TeraHertz Desorption Emission Spectroscopy (THz DES) of space relevant ices
• Insight into the origin of cometary ices from Rosetta/ROSINA mass spectrometer data
• Survival of Molecular Complexity under Recent Supernova Feedback: Detection of Hot Cores in RX J1713.7-3946