Chemistry of Complex Organic Molecules in the V883 Ori Disk Revealed by ALMA Band 3 Observations

Yamato, Yoshihide; Notsu, Shota; Aikawa, Yuri; Okoda, Yuki; Nomura, Hideko; Sakai, Nami

doi:10.3847/1538-3881/ad11d9

Cited by 4 publications

(2 citation statements)

References 146 publications

(225 reference statements)

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“…Generally, the D/H ratio of molecules (deuterium fractionation) reflects their formation processes as well as physical conditions and evolutionary stages. In fact, it has extensively been studied with observations of various deuterated species of not only CH 3 OH but also other molecules over the various regions, such as starless cores (e.g., Bizzocchi et al 2014;Ambrose et al 2021), both low-mass and high-mass protostars (e.g., Bianchi et al 2017aBianchi et al , 2017bJørgensen et al 2018;Taquet et al 2019;Manigand et al 2020;Drozdovskaya et al 2022;van Gelder et al 2022;Yamato et al 2024), andcomets (e.g., Drozdovskaya et al 2021;Müller et al 2022). In these studies, the D/H ratios toward low-mass protostars are found to reach up to 10%.…”

Section: Introductionmentioning

confidence: 99%

CH₃OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335

Okoda,

Oya,

Sakai

et al. 2024

ApJ

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Deuterium fractionation in the closest vicinity of a protostar is important in understanding its potential heritage to a planetary system. Here, we have detected the spectral line emission of CH3OH and its three deuterated species, CH2DOH, CHD2OH, and CH3OD, toward the low-mass protostellar source B335 at a resolution of 0.″03 (5 au) with Atacama Large Millimeter/submillimeter Array. They have a ring distribution within the radius of 24 au with the intensity depression at the continuum peak. We derive the column densities and abundance ratios of the above species at six positions in the disk/envelope system as well as the continuum peak. The D/H ratio of CH3OH is ∼[0.03–0.13], which is derived by correcting the statistical weight of 3 for CH2DOH. The [CHD2OH]/[CH2DOH] ratio is derived to be higher ([0.14–0.29]). On the other hand, the [CH2DOH]/[CH3OD] ratio ([4.9–15]) is higher than the statistical ratio of 3 and is comparable to those reported for other low-mass sources. We study the physical structure on a few astronomical unit scales in B335 by analyzing the CH3OH (183,15 − 182,16, A) and HCOOH (120,12 − 110,11) line emission. Velocity structures of these lines are reasonably explained as the infalling-rotating motion. The protostellar mass and the upper limit to the centrifugal barrier are thus derived to be 0.03–0.07 M ⊙ and <7 au, respectively, showing that B335 harbors a young protostar with a tiny disk structure. Such youth of the protostar may be related to the relatively high [CH2DOH]/[CH3OH] ratio.

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Section: Introductionmentioning

confidence: 99%

CH₃OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335

Okoda,

Oya,

Sakai

et al. 2024

ApJ

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“…The values were found to be comparable with the local interstellar medium (ISM) value ( 12 C/ 13 C = 68; Milam et al 2005) or to show lower 12 C/ 13 C ratios toward source B (Jørgensen et al 2016(Jørgensen et al , 2018, which are consistent within the error with the local ISM value for source A (Manigand et al 2020). In the Class I low-mass young outbursting star V883 Ori, COMs are enriched in 13 C ( 12 C/ 13 C ∼20-30) (Yamato et al 2024).…”

Section: Introductionmentioning

confidence: 99%

Carbon Isotope Fractionation of Complex Organic Molecules in Star-forming Cores

Ichimura,

Nomura,

Furuya

2024

ApJ

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Recent high-resolution and sensitivity Atacama Large Millimeter/submillimeter Array observations have unveiled the carbon isotope ratios (12C/13C) of complex organic molecules (COMs) in a low-mass protostellar source. To understand the 12C/13C ratios of COMs, we investigated the carbon isotope fractionation of COMs from prestellar cores to protostellar cores with a gas-grain chemical network model. We confirmed that the 12C/13C ratios of small molecules are bimodal in the prestellar phase: CO and species formed from CO (e.g., CH3OH) are slightly enriched in 13C compared to the local interstellar medium (by ∼10%), while those from C and C+ are depleted in 13C owing to isotope exchange reactions. COMs are mainly formed on the grain surface and in the hot gas (> 100 K) in the protostellar phase. The 12C/13C ratios of COMs depend on which molecules the COMs are formed from. In our base model, some COMs in the hot gas are depleted in 13C compared to the observations. Thus, we additionally incorporate reactions between gaseous atomic C and H2O ice or CO ice on the grain surface to form H2CO ice or C2O ice, as suggested by recent laboratory studies. The direct C-atom addition reactions open pathways to form 13C-enriched COMs from atomic C and CO ice. We find that these direct C-atom addition reactions mitigate 13C-depletion of COMs, and the model with the direct C-atom addition reactions better reproduces the observations than our base model. We also discuss the impact of the cosmic-ray ionization rate on the 12C/13C ratio of COMs.

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Monte Carlo simulation of UV-driven synthesis of complex organic molecules on icy grain surfaces

Ochiai,

Ida,

Shoji

2024

A&A

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Complex organic molecules (COMs) have been widely observed in molecular clouds and protostellar environments. One of the formation mechanisms of COMs is radical reactions on the icy grain surface driven by UV irradiation. While many experiments have reported that various COMs (including biomolecules) can be synthesized under such ice conditions, the majority of the reaction processes are unclear. Complementary numerical simulations are necessary to unveil the synthetic process behind the formation of COMs. In this study, we develop a chemical reaction simulation using a Monte Carlo method. To explore the complex reaction network of COM synthesis, the model was designed to eliminate the need to prepare reaction pathways in advance and to keep computational costs low. This allows for broad parameter surveys and a global investigation of COM synthesis reactions. With this simulation, we investigate the chemical reactions occurring on icy dust surfaces during and after UV irradiation, assuming a protoplanetary disk environment. We aim to reveal the types of organic molecules produced in a disk and the formation mechanisms of COMs, in particular, amino acids and sugars. The Monte Carlo method we developed here produces reaction sequences by selecting a reaction from all candidate reactions at each calculation step, based on Arrhenius-type weighting. For our purpose, we significantly accelerated the calculation by adopting an approximate estimation of activation energy without expensive quantum chemical calculations. The results show that photodissociation and subsequent radical-radical reactions cause random rearrangement of the covalent bonds in the initial molecules composed of methanol, formaldehyde, ammonia, and water. Consequently, highly complex molecules such as amino acids and sugars were produced in a wide range of the initial conditions. We found that the final abundances of amino acids and sugars have extremely similar dependence on the atomic ratios of the initial molecules, which peak at $ C/H 0.1$-0.3 and $ O/H 0.3$-0.5, although the amino acids abundance is usually more than ten times higher than that of sugars. To understand this dependence, a semi-analytical formula was derived. Additionally, parameter surveys of temperature, photon energy, and other factors have suggested that the decomposition reactions of amino acids and sugars undergo a rapid transition within the threshold of a given parameter.

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Chemistry of Complex Organic Molecules in the V883 Ori Disk Revealed by ALMA Band 3 Observations

Cited by 4 publications

References 146 publications

CH₃OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335

CH₃OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335

Carbon Isotope Fractionation of Complex Organic Molecules in Star-forming Cores

Monte Carlo simulation of UV-driven synthesis of complex organic molecules on icy grain surfaces

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Chemistry of Complex Organic Molecules in the V883 Ori Disk Revealed by ALMA Band 3 Observations

Cited by 4 publications

References 146 publications

CH3OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335

CH3OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335

Carbon Isotope Fractionation of Complex Organic Molecules in Star-forming Cores

Monte Carlo simulation of UV-driven synthesis of complex organic molecules on icy grain surfaces

Contact Info

Product

Resources

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CH₃OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335

CH₃OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335