The ALMA-PILS survey: detection of CH3NCO towards the low-mass protostar IRAS 16293−2422 and laboratory constraints on its formation

Ligterink, N. F. W.; Coutens, A.; Kofman, Vincent; Müller, H. S. P.; Garrod, R. T.; Calcutt, H.; Wampfler, S. F.; Jørgensen, J. K.; Linnartz, H.; Dishoeck, E. F. van

doi:10.1093/mnras/stx890

Cited by 99 publications

(148 citation statements)

References 59 publications

(100 reference statements)

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“…In particular, with respect to KIDA, our values are smaller by a factor of 5-6 at 100 K, the temperature of the warm gas in hot corinos and outflow molecular shocks where iCOMs are abundantly detected (e.g. Bottinelli et al 2004Bottinelli et al , 2007Taquet et al 2015;Jorgensen et al 2016;Ligterink et al 2017;Lefloch et al 2012Lefloch et al , 2017Lefloch et al , 2018Codella et al 2017), and by a factor of 25-28 at 10 K, the temperature of prestellar cores where iCOMs are also detected (Bacmann et al 2012;Cernicharo et al 2012;Vastel et al 2014;Jimenez-Serra et al 2016) Additionally, the review of the literature regarding the DME and MF reactions with HCO + and H + 3 has also shown important differences between the rate coefficients reported in the KIDA and UDfA databases with respect to the available experimental data, and more accurate experiments and/or theoretical calculations are clearly needed to better understand the products of the reactions and the dependence on temperature.…”

Section: Impact On the Abundancesmentioning

confidence: 57%

Destruction of dimethyl ether and methyl formate by collisions with He⁺

Ascenzi

Cernuto

Balucani

et al. 2019

A&A

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Context. To correctly model the abundances of interstellar complex organic molecules (iCOMs) in different environments, both formation and destruction routes should be appropriately accounted for. While several scenarios have been explored for the formation of iCOMs via grain and gas-phase processes, much less work has been devoted to understanding the relevant destruction pathways, with special reference to (dissociative) charge exchange or proton transfer reactions with abundant atomic and molecular ions such as He + , H 3 + and HCO + . Aims. By using a combined experimental and theoretical methodology we provide new values for the rate coefficients and branching ratios (BRs) of the reactions of He + ions with two important iCOMs, namely dimethyl ether (DME) and methyl formate (MF). We also review the destruction routes of DME and MF by other two abundant ions, namely H 3 + and HCO + . Methods. Based on our recent laboratory measurements of cross sections and BRs for the DME/MF + He + reactions over a wide collision energy range (Cernuto et al. 2017, Phys. Chem. Chem. Phys. 19, 19554; 2018 ChemPhysChem 19, 51), we extend our theoretical insights on the selectivity of the microscopic dynamics to calculate the rate coefficients k(T ) in the temperature range from 10 to 298 K. We implement these new and revised kinetic data in a general model of cold and warm gas, simulating environments where DME and MF have been detected. Results. Due to stereodynamical effects present at low collision energies, the rate coefficients, BRs and temperature dependences here proposed differ substantially from those reported in KIDA and UDfA, two of the most widely used astrochemical databases. These revised rates impact the predicted abundances of DME and MF, with variations up to 40% in cold gases and physical conditions similar to those present in prestellar cores. Conclusions. This work demonstrates that the accuracy of astrochemical models can be improved by a thorough characterization of the destruction routes of iCOMs. The details of the chemical systems, indeed, can strongly affect their efficiency and significant deviations with respect to the commonly used Langevin model estimates are possible.

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Section: Impact On the Abundancesmentioning

confidence: 57%

Destruction of dimethyl ether and methyl formate by collisions with He⁺

Ascenzi

Cernuto

Balucani

et al. 2019

A&A

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“…On the base of Table ?? we may estimate the CH 3 NCO/HNCO ratio to be ∼ 0.6, about a factor of 3 bigger than the largest observational estimate 0.25 (Ligterink et al 2017). However, we did not expect to find a close agreement with the observational data, as the two species, CH 3 NCO and HNCO formed on the surface of dust grains, are photodesorbed and incorporated into the gas phase without any further interaction.…”

Section: Conclusion and Astrophysical Implicationsmentioning

confidence: 59%

“…This species has been recently detected in protostar environments (Ligterink et al 2017;Martín-Doménech et al 2017), the Orion cloud (Cernicharo et al 2016), and in comets (Goesmann et al 2015). Ligterink et al (2017) estimated the column density of CH 3 NCO towards the binary low-mass protostar IRAS 16293-2422 to be ∼ (3 − 4) × 10 15 and ∼ (6 − 9) × 10 15 cm −2 are obtained towards sources B and A, respectively. A similar value, 4 × 10 15 cm −2 , has been derived towards IRAS 16293-2422 B by Martín-Doménech et al (2017).…”

Section: Conclusion and Astrophysical Implicationsmentioning

confidence: 93%

Synthesis of Complex Organic Molecules in Soft X-Ray Irradiated Ices

Ciaravella

Jiménez-Escobar

Cecchi‐Pestellini

et al. 2019

ApJ

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We study the chemical evolution of H 2 O:CO:NH 3 ice mixtures irradiated with soft X-rays, in the range 250 − 1250 eV. We identify many nitrogen-bearing molecules such as e.g., OCN − , NH + 4 , HNCO, CH 3 CN, HCONH 2 , and NH 2 COCONH 2 . Several infrared features are compatible with glycine or its isomers.During the irradiation, we detected through mass spectroscopy many species desorbing the ice. Such findings support either the infrared identifications and reveal less abundant species with not clear infrared features. Among them, m/z = 57 has been ascribed to methyl isocyanate (CH 3 NCO), a molecule of prebiotic relevance, recently detected in protostellar environments.During the warm up after the irradiation, several infrared features including 2168 cm −1 band of OCN − , 1690 cm −1 band of formamide, and the 1590 cm −1 band associated to three different species, HCOO − , CH 3 NH 2 and NH + 3 CH 2 COO survive up to room temperature. Interestingly, many high masses have been also detected. Possible candidates are methyl-formate, (m/z = 60, HCOOCH 3 ), ethanediamide (m/z = 88, NH 2 COCONH 2 ), and N-acetyl-L-aspartic acid (m/z = 175). This latter species is compatible with the presence of the m/z = 43, 70 and 80 fragments.Photo-desorption of organics is relevant for the detection of such species in the gas-phase of cold environments, where organic synthesis in ice mantles should dominate. We estimate the gas-phase enrichment of some selected species in the light of a protoplanetary disc model around young solartype stars.

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“…With intrinsically narrower, symmetric line profiles, the disambiguation of nearby, partially overlapping lines is more straightforward. Specifically, the emission strength of lines of complex molecules is seen to peak in a region west-southwest of source B at about 0.5 from its continuum peak (e.g., Baryshev et al 2015;Coutens et al 2016;Jørgensen et al 2016;Lykke et al 2017;Ligterink et al 2017;Calcutt et al 2018). The offset can be explained by the effect of high optical depth of both line and continuum emission closer to the source center.…”

Section: Peak Location For Complex Organic Moleculesmentioning

confidence: 99%

The ALMA-PILS survey: gas dynamics in IRAS 16293−2422 and the connection between its two protostars

Wiel

Jacobsen

Jørgensen

et al. 2019

A&A

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Context. The majority of stars form in binary or higher order systems. The evolution of each protostar in a multiple system may start at different times and may progress differently. The Class 0 protostellar system IRAS 16293−2422 contains two protostars, "A" and "B", separated by ∼600 au and embedded in a single, 10 4 au scale envelope. Their relative evolutionary stages have been debated. Aims. We aim to study the relation and interplay between the two protostars A and B at spatial scales of 60 au up to ∼10 3 au. Methods. We selected molecular gas line transitions of the species CO, H 2 CO, HCN, CS, SiO, and C 2 H from the ALMA-PILS spectral imaging survey (329-363 GHz) and used them as tracers of kinematics, density, and temperature in the IRAS 16293−2422 system. The angular resolution of the PILS data set allows us to study these quantities at a resolution of 0.5 (60 au at the distance of the source).Results. Line-of-sight velocity maps of both optically thick and optically thin molecular lines reveal: (i) new manifestations of previously known outflows emanating from protostar A; (ii) a kinematically quiescent bridge of dust and gas spanning between the two protostars, with an inferred density between 4×10 4 cm −3 and ∼3×10 7 cm −3 ; and (iii) a separate, straight filament seemingly connected to protostar B seen only in C 2 H, with a flat kinematic signature. Signs of various outflows, all emanating from source A, are evidence of high-density and warmer gas; none of them coincide spatially and kinematically with the bridge. Conclusions. We hypothesize that the bridge arc is a remnant of filamentary substructure in the protostellar envelope material from which protostellar sources A and B have formed. One particular morphological structure appears to be due to outflowing gas impacting the quiescent bridge material. The continuing lack of clear outflow signatures unambiguously associated to protostar B and the vertically extended shape derived for its disk-like structure lead us to conclude that source B may be in an earlier evolutionary stage than source A.

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The ALMA-PILS survey: detection of CH3NCO towards the low-mass protostar IRAS 16293−2422 and laboratory constraints on its formation

Cited by 99 publications

References 59 publications

Destruction of dimethyl ether and methyl formate by collisions with He⁺

Destruction of dimethyl ether and methyl formate by collisions with He⁺

Synthesis of Complex Organic Molecules in Soft X-Ray Irradiated Ices

The ALMA-PILS survey: gas dynamics in IRAS 16293−2422 and the connection between its two protostars

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The ALMA-PILS survey: detection of CH3NCO towards the low-mass protostar IRAS 16293−2422 and laboratory constraints on its formation

Cited by 99 publications

References 59 publications

Destruction of dimethyl ether and methyl formate by collisions with He+

Destruction of dimethyl ether and methyl formate by collisions with He+

Synthesis of Complex Organic Molecules in Soft X-Ray Irradiated Ices

The ALMA-PILS survey: gas dynamics in IRAS 16293−2422 and the connection between its two protostars

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Destruction of dimethyl ether and methyl formate by collisions with He⁺

Destruction of dimethyl ether and methyl formate by collisions with He⁺