Suchergebnisse

[Context] Studies of Class 0 objects allow to characterize the dynamical processes taking place at the onset of the star formation process and to determine the physical mechanisms responsible for the outcome of the collapse. Observations of dense gas tracers allow for the characterization of key kinematics of the gas that are directly involved in the star formation process, such as infall, outflow, and rotation. [Aims] This work is aimed at investigating the molecular line velocity profiles of the Class 0 protostellar object B335 and attempts to place constraints on the infall motions happening in the circumstellar gas of the object. [Methods] We present observations of C17O (1-0), C18O (1-0), and 12CO (2-1) transitions along with an analysis of spectral profiles at envelope radii between 100 and 860 au. [Results] C17O emission presents a double-peaked line profile distributed in a complex velocity field. Both peaks present an offset of 0.2-1 km s-1 from the systemic velocity of the source in the probed area. The optical depth of the C17O emission has been estimated and found to be less than 1, suggesting that the two velocity peaks trace two distinct velocity components of the gas in the inner envelope. [Conclusions] After discarding possible motions that could produce the complex velocity pattern, such as rotation and outflow, we conclude that infall motions are responsible for producing the velocity field. Because inside-out symmetric collapse cannot explain those observed profiles, it is suggested that these are produced by non-isotropic accretion from the envelope into the central source along the outflow cavity walls. ; This project has received funding from the European Research Council (ERC) under the European Union Horizon 2020 research and innovation program (MagneticYSOs project, grant agreement N° 679937). J.M.G. is supported by the grant AYA2017-84390-C2-R (AEI/FEDER, UE).

[Context] How simple organic matter appeared on Earth and the processes by which it transformed into more evolved organic compounds, which ultimately led to the emergence of life, is still an open topic. Different scenarios have been proposed, the main one assumes that simple organic compounds were synthesized, either in the gas phase or on the surfaces of dust grains, during the process of star formation and they were incorporated into larger bodies in the protoplanetary disk. The transformation of these simple organic compounds in more complex forms is still a matter of debate. Recent discoveries have pointed to catalytic properties of dust grains present in the early stellar envelope, which can nowadays be found in the form of chondrites. The significant infall of chondritic meteorites during the early periods of Earth suggests that the same reactions could have taken place in certain environments on the Earth's surface, with conditions more favorable for organic synthesis. [Aims] This work attempts to synthesize simple organic molecules, such as hydrocarbons and alcohols via Fischer-Tropsch-type reactions supported by different chondritic materials under early-Earth conditions, to investigate if organic synthesis can likely occur in this environment and to determine what the differences are in selectivity when using different types of chondrites. [Methods] Fischer-Tropsch-type reactions are investigated from mixtures of CO and H2 at 1 atm of pressure on the surfaces of different chondritic samples. The different products obtained are analyzed in situ by gas chromatography. [Results] Different Fischer-Tropsch reaction products are obtained in quantitative amounts. The formation of alkanes and alkenes being the main processes. The formation of alcohols also takes place in a smaller amount. Other secondary products were obtained in a qualitative way. [Conclusions] Chondritic material surfaces have been proven as good supports for the occurrence of organic synthesis. Under certain circumstances during the formation of Earth, they could have produced a suitable environment for these reactions to occur. ; J.M.T.-R. acknowledges financial support from research project PGC2018-097374-B-I00, funded by FEDER/Ministerio de Ciencia e Innovación – Agencia Estatal de Investigación. J.L. is grateful to ICREA Academia program and funding from Generalitat de Catalunya (2017 SGR 128). A.R. is indebted to the "Ramón y Cajal" program, MINECO project CTQ2017-89132-P, DIUE project 2017SGR1323, and funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 865657) for the project "Quantum Chemistry on Interstellar Grains" (QUANTUMGRAIN).