Theoretical Distribution of the Ammonia Binding Energy at Interstellar Icy Grains: A New Computational Framework

Tinacci, Lorenzo; Germain, Aurèle; Pantaleone, Stefano; Ferrero, Stefano; Ceccarelli, C.; Ugliengo, Piero

doi:10.1021/acsearthspacechem.2c00040

Cited by 28 publications

(37 citation statements)

References 81 publications

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“…Briefly, it is a time-dependent three-phase grain-gas chemistry code that computes the layered grain mantles structure. The gas-phase reaction network is an updated version of the KIDA 2014 network (https://kida.astrochem-tools.org/; Wakelam et al 2015), with the reactions described in Tinacci et al (2022a). The surface reactions are assumed to occur only in the last two formed mantle layers, the latter being in contact with the gas phase.…”

Section: Model Descriptionmentioning

confidence: 99%

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Tracking the Ice Mantle History in the Solar-type Protostars of NGC 1333 IRAS 4

Simone

Ceccarelli

Codella

et al. 2022

ApJL

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To understand the origin of the diversity observed in exoplanetary systems, it is crucial to characterize the early stages of their formation, represented by solar-type protostars. Likely, the gaseous chemical content of these objects directly depends on the composition of the dust-grain mantles formed before the collapse. Directly retrieving the ice mantle composition is challenging, but it can be done indirectly by observing the major components, such as NH3 and CH3OH at centimeter wavelengths, once they are released into the gas phase during the warm protostellar stage. We observed several CH3OH and NH3 lines toward three Class 0 protostars in NGC 1333 (IRAS 4A1, IRAS 4A2, and IRAS 4B), at high angular resolution (1″; ∼300 au) with the VLA interferometer at 24–26 GHz. Using a non-LTE LVG analysis, we derived a similar NH3/CH3OH abundance ratio in the three protostars (≤0.5, 0.015–0.5, and 0.003–0.3 for IRAS 4A1, 4A2, and 4B, respectively). Hence, we infer they were born from precollapse material with similar physical conditions. Comparing the observed abundance ratios with astrochemical model predictions, we constrained the dust temperature at the time of the mantle formation to be ∼17 K, which coincides with the average temperature of the southern NGC 1333 diffuse cloud. We suggest that a brutal event started the collapse that eventually formed IRAS 4A1, 4A2, and 4B, which, therefore, did not experience the usual prestellar core phase. This event could be the clash of a bubble with NGC 1333 South, which has previously been evoked in the literature.

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Section: Model Descriptionmentioning

confidence: 99%

“…Figure B1 (from Tinacci et al 2022b) shows the interplay between the gas phase and the grain surface chemistry for the NH 3 formation. The major NH 3 formation path is through the hydrogenation of frozen N on the grain surfaces (Jonusas et al 2020), as it is a fast and barrierless process.…”

Section: Appendix B Nh 3 Formationmentioning

confidence: 99%

Tracking the Ice Mantle History in the Solar-type Protostars of NGC 1333 IRAS 4

Simone

Ceccarelli

Codella

et al. 2022

ApJL

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“…In that connection, a natural extension of this work could be to also take into account BE distributions on amorphous and highly anisotropic surfaces, as this distribution is often readily available from quantum chemical calculations (e.g. Tinacci et al 2022;Ferrero et al 2020;Duflot et al 2021). Overall, we believe that the work presented here could pave the way for a stronger collaboration between the communities working on quantum chemical calculations of BEs, laboratory experiments, and ML, as the various approaches complement each other.…”

Section: Discussionmentioning

confidence: 84%

“…Quantum chemical calculation can also take into account BE distributions on amorphous and highly anisotropic surfaces (e.g. Tinacci et al 2022;Ferrero et al 2020;Duflot et al 2021). However, as these methods are computationally expensive, many astrochemical studies rely on the so-called linear addition method.…”

Section: Introductionmentioning

confidence: 99%

Predicting binding energies of astrochemically relevant molecules via machine learning

Villadsen

Ligterink

Andersen

2022

A&A

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Context. The behaviour of molecules in space is to a large extent governed by where they freeze out or sublimate. The molecular binding energy is therefore an important parameter for many astrochemical studies. This parameter is usually determined with time-consuming experiments, computationally expensive quantum chemical calculations, or the inexpensive yet relatively inaccurate linear addition method. Aims. In this work, we propose a new method for predicting binding energies (BEs) based on machine learning that is accurate, yet computationally inexpensive. Methods. We created a machine-learning (ML) model based on Gaussian process regression (GPR) and trained it on a database of BEs of molecules collected from laboratory experiments presented in the literature. The molecules in the database are categorised by their features, such as mono- or multilayer coverage, binding surface, functional groups, valence electrons, and H-bond acceptors and donors. Results. We assessed the performance of the model with five-fold and leave-one-molecule-out cross validation. Predictions are generally accurate, with differences between predicted binding energies and values from the literature of less than ±20%. We used the validated model to predict the binding energies of 21 molecules that were recently detected in the interstellar medium, but for which binding energy values are unknown. We used a simplified model to visualise where the snow lines of these molecules would be located in a protoplanetary disk. Conclusions. This work demonstrates that ML can be employed to accurately and rapidly predict BEs of molecules. Machine learning complements current laboratory experiments and quantum chemical computational studies. The predicted BEs will find use in the modelling of astrochemical and planet-forming environments.

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“…They are also deuterated by abundant D atoms, which are formed by dissociative recombination of H 2 D + . NH 3 and NH 2 D formed on cold grain surfaces, however, remain in the ice phase, and desorbed only inefficiently via non-thermal desorption at low temperatures (Hama & Watanabe 2013;Martín-Doménech et al 2014;Tinacci et al 2022).…”

Section: Resultsmentioning

confidence: 99%

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

Yamato¹,

Furuya²,

Aikawa³

et al. 2022

Preprint

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The nitrogen chemical evolution during star and planet formation is still not fully understood. Ammonia (NH 3 ) is a key specie in the understanding of the molecular evolution in star-forming clouds and nitrogen isotope fractionation. In this paper, we present high spatial resolution observations of multiple emission lines of NH 3 toward the protobinary system NGC1333 IRAS4A with Karl G. Jansky Very Large Array (VLA). We spatially resolved the binary (hereafter 4A1 and 4A2) and detected compact emission of NH 3 transitions with high excitation energies ( 100 K) from the vicinity of the protostars, indicating the NH 3 ice has sublimated at the inner hot region. The NH 3 column density is estimated to be ∼10 17 -10 18 cm −2 . We also detected two NH 2 D transitions, allowing us to constrain the deuterium fractionation of ammonia. The NH 2 D/NH 3 ratios are as high as ∼0.3-1 in both 4A1 and 4A2. From the comparisons with the astrochemical models in the literature, the high NH 2 D/NH 3 ratios suggest that the formation of NH 3 ices mainly started in the prestellar phase after the formation of bulk water ice finished, and that the primary nitrogen reservoir in the star-forming cloud could be atomic nitrogen (or N atoms) rather than nitrogen-bearing species such as N 2 and NH 3 . The implications on the physical properties of IRAS4A cores are discussed as well.

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Theoretical Distribution of the Ammonia Binding Energy at Interstellar Icy Grains: A New Computational Framework

Cited by 28 publications

References 81 publications

Tracking the Ice Mantle History in the Solar-type Protostars of NGC 1333 IRAS 4

Tracking the Ice Mantle History in the Solar-type Protostars of NGC 1333 IRAS 4

Predicting binding energies of astrochemically relevant molecules via machine learning

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

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