Article
Astronomy & Astrophysics
H. Luthra, V Wakelam, M. K. Sharma, S. Chandra
Summary: Since the 1930s, more than 250 molecules have been discovered in the interstellar medium, and with the development of more sensitive telescopes, we keep detecting new, more complex species. Among them, methanimine (CH2NH) is considered a pre-biotic molecule and has been observed in various interstellar sources. However, previous models failed in reproducing the observed abundance of CH2NH in cold cores. In this study, we tested new proposed reactions and explored the sensitivity of CH2NH abundance to different factors, and successfully reproduced the detections in cold cores Ori-3N and L183.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
O. Sipilae, L. Colzi, E. Roueff, P. Caselli, F. Fontani, E. Wirstroem
Summary: In this study, a new gas-grain chemical model for the combined isotopic fractionation of carbon and nitrogen in molecular clouds is presented. The results show significant deviations and time-dependent variations in isotopic abundance ratios as a function of physical conditions and time. Additionally, the abundance ratios between different isotopic forms of molecules also exhibit some levels of fractionation due to newly included exchange reactions.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Keshav Kumar Singh, Poonam Tandon, Rajesh Kumar, Alka Misra, Shivani, Manisha Yadav, Aftab Ahmad, Manoj Kumar Chaudhary
Summary: Aminomethanol is an important precursor of interstellar glycine, and a two-step formation pathway has been proposed for its formation in interstellar ice. The study found that the proposed pathway is efficient in ice, with CH2NH identified as the starting reactant for aminomethanol.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Zainab Awad, Serena Viti
Summary: Observations of diffuse clouds have found high abundances of simple hydrocarbons, challenging conventional gas-phase chemical models. Recent experimental results suggest that photodecomposition of hydrogenated amorphous carbon (HAC) and solid hexane can release a range of hydrocarbons into the gas phase. This study explores the feasibility of a 'top-down' or degradation mechanism for the formation of simple hydrocarbons in diffuse clouds.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Azrael A. von Prochazka, T. J. Millar
Summary: The study reveals that the abundances of NH3 in both gas phase and solid state are sensitive to gas-grain cycling within the system, and the degree of chemical complexity achievable at later stages of the cloud's chemical evolution is indeed influenced by the manner in which the gas-grain cycling occurs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
G. Esplugues, M. Rodriguez-Baras, D. San Andres, D. Navarro-Almaida, A. Fuente, P. Riviere-Marichalar, A. Sanchez-Monge, M. N. Drozdovskaya, S. Spezzano, P. Caselli
Summary: In this study, we analyzed the sulphur chemistry in the envelope of the Class 0 source B 335 using observations and modeling techniques. We detected 20 sulphur species in B 335, with a total gas-phase S abundance similar to other Class 0 objects. However, there were significant differences in the abundances between sulphur carbon chains and sulphur molecules containing oxygen and nitrogen. Our results suggest that B 335 is a source rich in sulphur carbon chains, unlike other Class 0 sources. We also found that the presence of HCS+ and low rotational temperatures indicate a moderate or low density of the envelope. Cosmic ray ionisation rate and density variations play a significant role in the abundances of certain sulphur species.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
G. Esplugues, A. Fuente, D. Navarro-Almaida, M. Rodriguez-Baras, L. Majumdar, P. Caselli, V Wakelam, E. Roueff, R. Bachiller, S. Spezzano, P. Riviere-Marichalar, R. Martin-Domenech, G. M. Munoz Caro
Summary: This study investigates the abundances of thioformaldehyde and its deuterated versions in starless cores located in different star-forming regions. The results show that the deuterium fractionation ratios can be used as powerful tools to determine the chemical evolutionary stage of these cores.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Brandt A. L. Gaches, Thomas G. Bisbas, Shmuel Bialy
Summary: This study investigates the impact of cosmic-ray attenuation on the emission of carbon cycle species in molecular clouds. The findings suggest that constant ionization rate models fail to reproduce the actual situation, highlighting the need for column-dependent cosmic-ray ionization rate prescriptions.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
V. Wakelam, P. Gratier, M. Ruaud, R. Le Gal, L. Majumdar, J. -C. Loison, K. M. Hickson
Summary: This paper presents the chemical composition of five cold clumps identified by the Planck mission, with radiative transfer analysis and chemical models used to constrain physical conditions and molecular column densities. The study reveals significant chemical differences among the sources, with poorer composition compared to TMC-1 CP. The chemical model successfully reproduces observational abundances for most species, indicating that the sources may be less evolved than TMC-1.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
N. Bulut, O. Roncero, A. Aguado, J-C Loison, D. Navarro-Almaida, V Wakelam, A. Fuente, E. Roueff, R. Le Gal, P. Caselli, M. Gerin, K. M. Hickson, S. Spezzano, P. Riviere-Marichalar, T. Alonso-Albi, R. Bachiller, I Jimenez-Serra, C. Kramer, B. Tercero, M. Rodriguez-Baras, S. Garcia-Burillo, J. R. Goicoechea, S. P. Trevino-Morales, G. Esplugues, S. Cazaux, B. Commercon, J. Laas, J. Kirk, V Lattanzi, R. Martin-Domenech, G. Munoz-Caro, J. Pineda, D. Ward-Thompson, M. Tafalla, N. Marcelino, J. Malinen, R. Friesen, B. M. Giuliano, M. Agundez, A. Hacar
Summary: Carbon monosulphide (CS) is a common gas-phase S-bearing molecule in cold dark molecular clouds, and its reaction rate with O at temperatures below 150 K has been calculated using theoretical methods. The study shows that the reaction rate at 10 K is negligible, consistent with experimental data predictions.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
N. Marcelino, C. Puzzarini, M. Agundez, R. Fuentetaja, B. Tercero, P. de Vicente, J. Cernicharo
Summary: We report the discovery of HSO in several cold dark clouds, confirmed by observing rotational transitions. The HSO column densities were obtained and the abundances relative to H-2 were calculated. The widespread presence of HSO in cold dense cores suggests the need for further observations to understand its chemical production mechanisms.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Y. Lin, S. Spezzano, P. Caselli
Summary: The first detection of doubly deuterated methanol in pre-stellar cores is reported, indicating the inheritance of material across the star and planet formation process. The study reveals a D/H ratio of 0.8-1.9% in pre-stellar cores, consistent with measurements in more evolved objects, suggesting a direct chemical link in the pre-stellar stage. The column density ratios of CHD2OH/CH2DOH in the pre-stellar cores indicate an efficient formation mechanism of CHD2OH, while the evolutionary trend of methanol deuteration is observed in early-stage cores.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Y. Gong, F. J. Du, C. Henkel, A. M. Jacob, A. Belloche, J. Z. Wang, K. M. Menten, W. Yang, D. H. Quan, C. T. Bop, G. N. Ortiz-Leon, X. D. Tang, M. R. Rugel, S. Liu
Summary: In this study, the authors investigated the impact of the environment on the chemistry of protonated hydrogen cyanide (HCNH+). Their observations showed that HCNH+ is abundant in cold and quiescent regions, but deficient in active star-forming regions. The abundance of HCNH+ is negatively correlated with the H-2 column density, indicating its coevolution with cloud cores.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Qingkuan Meng, Qiang Chang, Gang Zhao, Donghui Quan, Masashi Tsuge, Xia Zhang, Yong Zhang, Xiao-Hu Li
Summary: In this study, we quantitatively explain the relationship between the desorption energy of hydrogen on a diamond-like carbon surface and the surface coverage through experiments and calculations. We derived a mathematical formula to calculate the effective desorption energy of hydrogen, which depends on the desorption energy of hydrogen on the substrate and the ratio of diffusion barrier to desorption energy. By recalculating these parameters based on experimental data, we achieved good agreement between theoretical and experimental results.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Megias, I Jimenez-Serra, J. Martin-Pintado, A. Vasyunin, S. Spezzano, P. Caselli, G. Cosentino, S. Viti
Summary: Recent observations of L1544 and L1498 show enhanced complex organic molecules (COMs) in the gas phase towards their outer and intermediate-density shells. High-sensitivity observations of L1517B reveal lower detection and abundance of COMs and COM precursors compared to L1544 and L1498. The chemical complexity in these starless cores seems to increase over time, with N-bearing molecules forming first followed by O-bearing COMs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Jean-Christophe Loison, Valentine Wakelam, Pierre Gratier, Kevin M. Hickson, Aurore Bacmann, Marcelino Agundez, Nuria Marcelino, Jose Cernicharo, Viviana Guzman, Maryvonne Gerin, Javier R. Goicoechea, Evelyne Roueff, Franck Le Petit, Jerome Pety, Asuncion Fuente, Pablo Riviere-Marichalar
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2019)
Article
Astronomy & Astrophysics
A. Coutens, N. F. W. Ligterink, J-C Loison, V Wakelam, H. Calcutt, M. N. Drozdovskaya, J. K. Jorgensen, H. S. P. Mueller, E. F. van Dishoeck, S. F. Wampfler
ASTRONOMY & ASTROPHYSICS
(2019)
Article
Astronomy & Astrophysics
A. T. Barnes, J. Kauffmann, F. Bigiel, N. Brinkmann, D. Colombo, A. E. Guzman, W. J. Kim, L. Szucs, V Wakelam, S. Aalto, T. Albertsson, N. J. Evans, S. C. O. Glover, P. F. Goldsmith, C. Kramer, K. Menten, Y. Nishimura, S. Viti, Y. Watanabe, A. Weiss, M. Wienen, H. Wiesemeyer, F. Wyrowski
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
V Wakelam, W. Iqbal, J-P Melisse, P. Gratier, M. Ruaud, I Bonnell
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
P. K. Humire, V Thiel, C. Henkel, A. Belloche, J-C Loison, T. Pillai, D. Riquelme, V Wakelam, N. Langer, A. Hernandez-Gomez, R. Mauersberger, K. M. Menten
ASTRONOMY & ASTROPHYSICS
(2020)
Article
Astronomy & Astrophysics
A. Coutens, B. Commercon, V. Wakelam
ASTRONOMY & ASTROPHYSICS
(2020)
Article
Astronomy & Astrophysics
Jean-Christophe Loison, Valentine Wakelam, Pierre Gratier, Kevin M. Hickson
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
V. C. Mota, A. J. C. Varandas, E. Mendoza, V. Wakelam, B. R. L. Galvao
Summary: Silicon monosulfide is a significant silicon-bearing molecule in circumstellar envelopes and star-forming regions, but its formation and destruction mechanisms remain unclear. This study calculated rate coefficients for the Si+SH -> SiS+H reaction over a temperature range and showed that the reaction is predicted to be fast, with a substantial increase at lower temperatures. Additionally, an astrochemical gas-grain model revealed that the inclusion of the Si+SH reaction can significantly impact the abundance of SiS gas-phase compared to H-2, aligning with observed abundances.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
A. Coutens, J. -C. Loison, A. Boulanger, E. Caux, H. S. P. Muller, V. Wakelam, S. Manigand, J. K. Jorgensen
Summary: In this work, the molecular composition of a solar-type protostar was analyzed using ALMA data, and the presence of 3-hydroxypropenal was tentatively detected in the interstellar medium. The abundance of 3-hydroxypropenal was found to be similar to 10(-4) relative to methanol. Additional isomers were also predicted to be present in higher abundance. Further spectroscopic studies are crucial to confirm these findings.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Danilo R. Campanha, Edgar Mendoza, Mateus X. Silva, Paulo F. G. Velloso, Miguel Carvajal, Valentine Wakelam, Breno R. L. Galvao
Summary: The impact of the Si + SO2 reaction on the abundances of astrochemically relevant molecules is investigated and it is found that only SO and SiO are produced as products. No other reaction pathways leading to the abundance of SiS have been identified. Furthermore, it is discovered that SiS is stable in collisions with O-2, and other reactions involving Si and S-bearing molecules are examined.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
V Wakelam, A. Coutens, P. Gratier, T. H. G. Vidal, N. Vaytet
Summary: The emission of several molecules from the L1451-mm FHSC candidate was observed, and a low-velocity and compact outflow was detected, supporting the hypothesis that L1451-mm is at an early protostellar stage.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
A. Clement, A. Taillard, V. Wakelam, P. Gratier, J. -c. Loison, E. Dartois, F. Dulieu, J. A. Noble, M. Chabot
Summary: This study models the formation process of interstellar ices, focusing on H2O, CO2, CO, and CH3OH. The research finds that dust temperature and visual extinction significantly influence the composition of ice, with the formation of CO2 being particularly affected by dust temperature under low visual extinction conditions.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
M. Agundez, J. -c. Loison, K. M. Hickson, V. Wakelam, R. Fuentetaja, C. Cabezas, N. Marcelino, B. Tercero, P. de Vicente, J. Cernicharo
Summary: We detected the presence of ethanol, acetone, and propanal in the cyanopolyyne peak of TMC-1, which are complex organic molecules known to be present in warm interstellar clouds but had never been observed in a starless core. This discovery adds new pieces to the puzzle of complex organic molecules in cold interstellar clouds, highlighting the chemical diversity of cold dense cores prior to star formation. The abundances of these molecules derived from observations are in reasonable agreement with the values calculated by a detailed chemical model.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
H. Luthra, V Wakelam, M. K. Sharma, S. Chandra
Summary: Since the 1930s, more than 250 molecules have been discovered in the interstellar medium, and with the development of more sensitive telescopes, we keep detecting new, more complex species. Among them, methanimine (CH2NH) is considered a pre-biotic molecule and has been observed in various interstellar sources. However, previous models failed in reproducing the observed abundance of CH2NH in cold cores. In this study, we tested new proposed reactions and explored the sensitivity of CH2NH abundance to different factors, and successfully reproduced the detections in cold cores Ori-3N and L183.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Dipen Sahu, Sheng-Yuan Liu, Ankan Das, Prasanta Garai, Valentine Wakelam
ASTROPHYSICAL JOURNAL
(2020)