Academic literature on the topic 'Star formation, astrochemistry'

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Journal articles on the topic "Star formation, astrochemistry"

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Jørgensen, Jes K., Arnaud Belloche, and Robin T. Garrod. "Astrochemistry During the Formation of Stars." Annual Review of Astronomy and Astrophysics 58, no. 1 (August 18, 2020): 727–78. http://dx.doi.org/10.1146/annurev-astro-032620-021927.

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Star-forming regions show a rich and varied chemistry, including the presence of complex organic molecules—in both the cold gas distributed on large scales and the hot regions close to young stars where protoplanetary disks arise. Recent advances in observational techniques have opened new possibilities for studying this chemistry. In particular, the Atacama Large Millimeter/submillimeter Array has made it possible to study astrochemistry down to Solar System–size scales while also revealing molecules of increasing variety and complexity. In this review, we discuss recent observations of the chemistry of star-forming environments, with a particular focus on complex organic molecules, taking context from the laboratory experiments and chemical models that they have stimulated. The key takeaway points include the following: ▪ The physical evolution of individual sources plays a crucial role in their inferred chemical signatures and remains an important area for observations and models to elucidate. ▪ Comparisons of the abundances measured toward different star-forming environments (high-mass versus low-mass, Galactic Center versus Galactic disk) reveal a remarkable similarity, which is an indication that the underlying chemistry is relatively independent of variations in their physical conditions. ▪ Studies of molecular isotopologues in star-forming regions provide a link with measurements in our own Solar System, and thus may shed light on the chemical similarities and differences expected in other planetary systems.
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Cridland, Alexander J., Christian Eistrup, and Ewine F. van Dishoeck. "Connecting planet formation and astrochemistry." Astronomy & Astrophysics 627 (July 2019): A127. http://dx.doi.org/10.1051/0004-6361/201834378.

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Combining a time-dependent astrochemical model with a model of planet formation and migration, we compute the carbon-to-oxygen ratio (C/O) of a range of planetary embryos starting their formation in the inner solar system (1–3 AU). Most of the embryos result in hot Jupiters (M ≥ MJ, orbital radius <0.1 AU) while the others result in super-Earths at wider orbital radii. The volatile and ice abundance of relevant carbon and oxygen bearing molecular species are determined through a complex chemical kinetic code that includes both gas and grain surface chemistry. This is combined with a model for the abundance of the refractory dust grains to compute the total carbon and oxygen abundance in the protoplanetary disk available for incorporation into a planetary atmosphere. We include the effects of the refractory carbon depletion that has been observed in our solar system, and posit two models that would put this missing carbon back into the gas phase. This excess gaseous carbon then becomes important in determining the final planetary C/O because the gas disk now becomes more carbon rich relative to oxygen (high gaseous C/O). One model, where the carbon excess is maintained throughout the lifetime of the disk results in hot Jupiters that have super-stellar C/O. The other model deposits the excess carbon early in the disk life and allows it to advect with the bulk gas. In this model the excess carbon disappears into the host star within 0.8 Myr, returning the gas disk to its original (substellar) C/O, so the hot Jupiters all exclusively have substellar C/O. This shows that while the solids tend to be oxygen rich, hot Jupiters can have super-stellar C/O if a carbon excess can be maintained by some chemical processing of the dust grains. The atmospheric C/O of the super-Earths at larger radii are determined by the chemical interactions between the gas and ice phases of volatile species rather than the refractory carbon model. Whether the carbon and oxygen content of the atmosphere was accreted primarily by gas or solid accretion is heavily dependent on the mass of the atmosphere and where in the disk the growing planet accreted.
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Tan, Jonathan C. "Fire from Ice - Massive Star Birth from Infrared Dark Clouds." Proceedings of the International Astronomical Union 13, S332 (March 2017): 139–52. http://dx.doi.org/10.1017/s1743921317009784.

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AbstractI review massive star formation in our Galaxy, focussing on initial conditions in Infrared Dark Clouds (IRDCs), including the search for massive pre-stellar cores (PSCs), and modeling of later stages of massive protostars, i.e., hot molecular cores (HMCs). I highlight how developments in astrochemistry, coupled with rapidly improving theoretical/computational and observational capabilities are helping to improve our understanding of the complex process of massive star formation.
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Ishak, B. "Introduction to astrochemistry: chemical evolution from interstellar clouds to star and planet formation." Contemporary Physics 60, no. 3 (June 20, 2019): 262. http://dx.doi.org/10.1080/00107514.2019.1621938.

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Aalto, S. "Astrochemistry and star formation in nearby galaxies: from galaxy disks to hot nuclei." EAS Publications Series 75-76 (2015): 73–80. http://dx.doi.org/10.1051/eas/1575013.

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Mason, Nigel J., Binukumar Nair, Sohan Jheeta, and Ewelina Szymańska. "Electron induced chemistry: a new frontier in astrochemistry." Faraday Discuss. 168 (2014): 235–47. http://dx.doi.org/10.1039/c4fd00004h.

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The commissioning of the ALMA array and the next generation of space telescopes heralds the dawn of a new age of Astronomy, in which the role of chemistry in the interstellar medium and in star and planet formation may be quantified. A vital part of these studies will be to determine the molecular complexity in these seemingly hostile regions and explore how molecules are synthesised and survive. The current hypothesis is that many of these species are formed within the ice mantles on interstellar dust grains with irradiation by UV light or cosmic rays stimulating chemical reactions. However, such irradiation releases many secondary electrons which may themselves induce chemistry. In this article we discuss the potential role of such electron induced chemistry and demonstrate, through some simple experiments, the rich molecular synthesis that this may lead to.
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Nishimura, Yuri, Takashi Shimonishi, Yoshimasa Watanabe, Nami Sakai, Yuri Aikawa, Akiko Kawamura, Kotaro Kohno, and Satoshi Yamamoto. "Molecular Composition of Local Dwarf Galaxies: Astrochemistry in Low-metallicity Environments." Proceedings of the International Astronomical Union 14, S344 (August 2018): 182–85. http://dx.doi.org/10.1017/s1743921318006336.

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AbstractTo investigate molecular composition of low-metallicity environments, we conducted spectral line survey observations in the 3 mm band toward three dwarf galaxies, the Large Magellanic Cloud, IC 10, and NGC 6822 with the Mopra 22 m, the Nobeyama 45 m and the IRAM 30 m, respectively. The rotational transitions of CCH, HCN, HCO+, HNC, CS, SO, 13CO, and 12CO were detected in all three galaxies. We found that the spectral intensity patterns are similar to one another regardless of star formation activities. Compared with Solar-metallicity environments, the molecular compositions of dwarf galaxies are characterized by (1) deficient nitrogen-bearing molecules and (2) enhanced CCH and suppressed CH3OH. These are interpreted (1) as a direct consequence of the lower elemental abundance of nitrogen, and (2) as a consequence of extended photon dominated regions in cloud peripheries due to the lower abundance of dust grains, respectively.
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Harada, Nanase. "High-Temperature Chemistry in External Galaxies." Proceedings of the International Astronomical Union 13, S332 (March 2017): 25–36. http://dx.doi.org/10.1017/s1743921317006755.

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AbstractIn external galaxies, some galaxies have higher activities of star formation and central supermassive black holes. The interstellar medium in those galaxies can be heated by different mechanisms such as UV-heating, X-ray heating, cosmic-ray heating, and shock/mechanical heating. Chemical compositions can also be affected by those heating mechanisms. Observations of many molecular species in those nearby galaxies are now possible with the high sensitivity of Atacama Large Millimeter/sub-millimeter Array (ALMA). Here I cover different chemical models for those heating mechanisms. In addition, I present recent ALMA results of extragalactic astrochemistry including our results of a face-on galaxy M83 and an infrared-luminous merger NGC 3256.
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Qin, Sheng-Li, Tie Liu, Xunchuan Liu, Paul F. Goldsmith, Di Li, Qizhou Zhang, Hong-Li Liu, et al. "ATOMS: ALMA Three-millimeter Observations of Massive Star-forming regions – VIII. A search for hot cores by using C2H5CN, CH3OCHO, and CH3OH lines." Monthly Notices of the Royal Astronomical Society 511, no. 3 (January 29, 2022): 3463–76. http://dx.doi.org/10.1093/mnras/stac219.

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ABSTRACT Hot cores characterized by rich lines of complex organic molecules are considered as ideal sites for investigating the physical and chemical environments of massive star formation. We present a search for hot cores by using typical nitrogen- and oxygen-bearing complex organic molecules (C2H5CN, CH3OCHO, and CH3OH), based on ALMA Three-millimeter Observations of Massive Star-forming regions (ATOMS). The angular resolutions and line sensitivities of the ALMA observations are better than 2 arcsec and 10 mJy beam−1, respectively. A total of 60 hot cores are identified with 45 being newly detected, in which the complex organic molecules have high gas temperatures (&gt; 100 K) and hot cores have small source sizes (&lt; 0.1 pc). So far, this is the largest sample of hot cores observed with similar angular resolution and spectral coverage. The observations have also shown nitrogen and oxygen differentiation in both line emission and gas distribution in 29 hot cores. Column densities of CH3OH and CH3OCHO increase as rotation temperatures rise. The column density of CH3OCHO correlates tightly with that of CH3OH. The pathways for production of different species are discussed. Based on the spatial position difference between hot cores and ultracompact H ii (UC H ii) regions, we conclude that 24 hot cores are externally heated, while the other hot cores are internally heated. The observations presented here will potentially help establish a hot core template for studying massive star formation and astrochemistry.
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Caselli, P., O. Sipilä, and J. Harju. "Deuterated forms of H 3 + and their importance in astrochemistry." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2154 (August 5, 2019): 20180401. http://dx.doi.org/10.1098/rsta.2018.0401.

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At the low temperatures (approx. 10 K) and high densities (approx. 100 000 H 2 molecules per cm −3 ) of molecular cloud cores and protostellar envelopes, a large amount of molecular species (in particular those containing C and O) freeze-out onto dust grain surfaces. It is in these regions that the deuteration of H 3 + becomes very efficient, with a sharp abundance increase of H 2 D + and D 2 H + . The multi-deuterated forms of H 3 + participate in an active chemistry: (i) their collision with neutral species produces deuterated molecules such as the commonly observed N 2 D + , DCO + and multi-deuterated NH 3 ; (ii) their dissociative electronic recombination increases the D/H atomic ratio by several orders of magnitude above the D cosmic abundance, thus allowing deuteration of molecules (e.g. CH 3 OH and H 2 O) on the surface of dust grains. Deuterated molecules are the main diagnostic tools of dense and cold interstellar clouds, where the first steps toward star and protoplanetary disc formation take place. Recent observations of deuterated molecules are reviewed and discussed in view of astrochemical models inclusive of spin-state chemistry. We present a new comparison between models based on complete scrambling (to calculate branching ratio tables for reactions between chemical species that include protons and/or deuterons) and models based on non-scrambling (proton hop) methods, showing that the latter best agree with observations of NH 3 deuterated isotopologues and their different nuclear spin symmetry states. This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H 3 + , H 5 + and beyond’.
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Dissertations / Theses on the topic "Star formation, astrochemistry"

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Von, Procházka Azrael Alžbeta. "Prestellar and hot molecular cores : astrochemistry in the early stages of star formation." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603432.

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This thesis addresses the problem of complex molecule formation in the prestellar and hot core stages of interstellar star formation. We have enhanced a modified rates chemical code to include calculations of physisorption and chemisorption on interstellar grains consisting of amorphous carbon, graphite PAH particles, para-site PAH particles, and silicates as well as calculations of non-thermal desorption via cosmic ray heating, H2 desorption, and cosmic ray-induced photodesorption. We incorporate a time-dependent, warm-up parameter in order to self-consistently treat the chemistry of our dark cloud and hot core models. We find that different dark cloud species achieve better observational agreement for different desorption conditions and that molecules which are inefficiently destroyed in the dark cloud tend to demonstrate an enhanced presence in the early chemistry of the hot core. During the warm up, we observe temporary enhancement of a number of species on the grain surface and • suggest this is due to the physical cycling of molecular material between the gas and solid states as well as the presence of fast barrier-possessing reactions which occur between particles on the grain surface. The presence of a time-dependent warm up also allows a transient period of N-rich chemistry to occur in the gas phase and indicates a number of possibilities which may ::allow the simultaneous occurrence of cyanide and complex organic species in star-forming molecular clouds. We argue that for high NH3 abundances, alkyl-cation transfer reactions may proceed sufficiently rapidly that complex organic species and nitriles can coexist in both compact and ultra-compact hot molecular cores.
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Hernandez, Gomez Antonio. "IRAS 16293-2422 : des longueurs d'onde centimétriques à l'infrarouge lointain et détermination de sa structure tridimensionnelle." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30004.

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Dans cette thèse, nous présentons une étude observationnelle et multifréquence des propriétés d'IRAS16293-2422 (I16293), un système d'étoiles multiples de faible masse et de type solaire bien étudié, qui se trouve dans le nuage sombre L1689N dans le complexe d'Ophiuchus. I16293 est la source prototype pour les études d'astrochimie en raison de sa richesse en raies moléculaires, elle constitue un laboratoire idéal pour étudier non seulement la formation de systèmes stellaires, mais également la chimie pendant les premiers stades de la formation des étoiles. Dans ce travail, nous mettrons particulièrement l'accent sur les molécules azotée, car ces espèces sont des outils puissants pour mesurer les propriétés chimiques, cinématiques et dynamiques des régions de formation d'étoiles dans un large éventail de conditions physiques. La première partie est dédié à l'analyse des composants individuels d'I16293 à partir d'observations dans le continuum aux longueurs d'onde centimétriques et millimétriques. Nous avons mesuré l'émission maser à 22 GHz obtenues avec l'interféromètre de très longue ligne de base (VLBA) et obtenu une estimation plus précise de la distance d'I16293, 141(+30,-21)pc. À partir d'observations à haute résolution angulaire avec le VLA et ALMA, nous avons suivi l'astrométrie des objets individuels du système pendant près de 30 ans. Nous présentons un modèle complet de transfert radiatif de la structure de cette source. Les profils de densité et de température nécessaires pour expliquer les propriétés de la source B sont très similaires à ceux attendus pour un premier coeur hydrostatique. Ce fait, combiné à l'absence d'émission centimétrique libre-libre, pourrait indiquer que la source B vient tout juste d'atteindre la phase protostellaire. La seconde partie est consacrée à une étude de la chimie d'I16293 à partir d'observations des molécules azotées dans une large gamme de fréquences avec les radiotélescopes IRAM-30m, APEX, JCMT et l'instrument HIFI à bord de l'observatoire spatial Herschel. Nous avons extrait les transitions de rotation de l'acide isocyanurique (HNCO) à partir de ces données et utilisé un modèle de transfert radiatif hors de l'équilibre thermodynamique local (ETL) pour reproduire les profils observés des raies. À partir de ce modèle, nous concluons I16293 est formée de trois régions d'émission: un composant dense, compact et chaud, un composant chaud et étendu associé à la partie interne de l'enveloppe et une couche plus étendue et froide associée à la partie la plus extérieure de l'enveloppe. L'émission produite par chacune de ces régions interagit avec les autres, en conséquence, notre analyse contraint les propriétés des différentes régions, et établit également leurs positions relatives le long de la ligne de visée. Nous avons calculé le profil d'abondance de HNCO pour l'enveloppe d'I16293 avec le code chimique Nautilus, qui est tout à fait compatible avec les abondances déterminées par notre modèle de transfert radiatif. D'autre part, les profils de raie de cyanure (CN) dans I16293 sont beaucoup plus complexes que les profils de HNCO, car ils présentent une absorption profonde. Nous détectons les transitions de rotation du CN correspondant aux niveaux J = 1-0 à J = 5-4, nous avons utilisé ces raies pour tester la distribution de cette molécule à différentes échelles spatiales. Nous avons utilisé un modèle LTE dans CASSIS et défini un modèle distinct pour chaque transition. Afin de reproduire correctement les profils de raie, il est nécessaire de prendre en compte un composant plus étendu que l'enveloppe d'I16293 définie précédemment dans la littérature. Finalement, nous dérivons les rapports d'abondance entre CN et ses isotopes 13CN et C15N. Dans leur ensemble, les données présentées dans cette thèse nous ont permis de contraindre la structure d'I16293 depuis les échelles qui correspondent à ses proto-étoiles individuelles (~10 AU) jusqu'à l'échelle de son enveloppe étendue (≥ 10,000 AU)
In this thesis we present a multi-frequency observational study of the properties of IRAS 16293-2422 (I16293), a very-well studied low-mass solar-type multiple stellar system located within the Ophiuchus complex. Because I16293 is the prototype source for astrochemistry due to its wealth of molecular lines, it provides a suitable laboratory to study not only the physics of clustered star-formation but also the chemistry in early stages of this process. In this thesis, we will place special emphasis on nitrogen-bearing molecules present in I16293since these species are known to be powerful tools to derive chemical, kinematic and dynamic properties of star-forming regions over a wide range of conditions. The first part of this work is based on the analysis of the individual components of I16293 from interferometric centimeter -and millimeter- wavelength continuum observations. Since the correct interpretation of the observations and their corresponding modelling strongly depend on the accurate measurement of its distance, we have measured the parallax to its H2O maser emission at 22.2 GHz based on archival Very Large Baseline Array (VLBA) observations, obtaining a precise estimation of the distance of 141(+30,-21)pc. From high angular resolution observations with the Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA), we followed the astrometry of the individual objects in the system for almost 30 years. We have seen that the properties of source B are remarkable because its spectrum indicates that its emission is dominated by thermal dust radiation. We present a full radiative transfer modelling of the structure of this source. The density and temperature profiles needed to explain the observational properties of source B resemble those expected for first hydrostatic cores. This fact, combined with the lack of free- free centimeter emission, might indicate that source B is just entering the protostellar phase. In the second part of the thesis we focus on the chemistry of I16293 based on single-dish observations of nitrogen-bearing molecules obtained with the radiotelescopes IRAM-30m, APEX, JCMT and the HIFI instrument on-board the Herschel Space Observatory over a wide frequency range from 80 GHz to 1 THz. We have extracted the rotational transitions of isocyanic acid (HNCO) from the observations and used a radiative transfer model out of Local Thermodynamical Equilibrium (non-LTE) to reproduce the observed line profiles. We conclude that I16293 can be modelled considering three regions: a dense, compact and warm component related with the hot corino, a warm and extended component associated with the innermost part of the envelope and a more extended and cold layer associated with the outermost part of the envelope. It is important to emphasize that the emission produced by these regions interacts one with another. As a consequence, our analysis not only constraints the properties of the different regions, but also establishes their relative positions along the line of sight. An HNCO abundance profile for the envelope of I16293 computed with the chemical code Nautilus shows a good agreement with the abundances derived from our radiative transfer model. On the other hand, the lines of cyanide (CN) have much more complex profiles since they show hyperfine structure and present deep absorptions. Indeed, since we detect the CN rotational transitions from J = 1 - 0 to J = 5 - 4 level, we have used an LTE model in CASSIS and defined a separate model for each transition. We noted that an extended emission larger than the envelope of I16293 is needed to correctly model the line profiles. We also derived the abundance ratio between CN and its isotopes 13CN and C15N.Taken together, the results presented here enabled us to constrain the structure of IRAS 16293- 2422 from the scale of its individual protostars (~ 10 AU) up to the scale of its extended envelope (~ 10,000 AU)
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Stephán, Gwendoline. "Modélisation de la chimie dans les régions de formation d'étoiles massives avec des PDRs internes." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEO012/document.

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Les conditions menant à la formation des étoiles massives sont toujours étudiées mais un scénario de leur évolution a été avancé : lors de l’effondrement d’un coeur froid pré-stellaire sous l’effet de la gravité, le milieu se réchauffe et entre ainsi dans la phase de coeur chaud moléculaire (CCM). La proto-étoile centrale en formation accrète de la matière, augmentant sa masse et sa luminosité, et finalement devient suffisamment évoluée pour émettre des photons UV qui irradient l’entourage de l’étoile formant ainsi une région HII hypercompact (HC), puis une région HII ultracompact (UC). À ce stade, une région de photo-dissociation (PDR) se forme entre la région HII et le coeur moléculaire. La composition chimique du milieu nous permet de connaître les processus physiques ayant lieu pendant les différentes phases de la formation des étoiles. De plus, la chimie nous permet également de déterminer le stade de l’évolution d’un objet astrophysique par l’utilisation de codes chimiques incluant l’évolution temporelle de la température et du champ de rayonnement. Jusqu’à présent, peu d’études ont examiné les PDRs internes et cela a été uniquement en présence d’une cavité formée par un écoulement (appelé ici outflow) de matière depuis les pôles de la proto-étoile vers le milieu environnant. La connaissance de ces régions uniques autour des régions HII hypercompact et ultracompact restent donc à approfondir. Ma thèse de doctorat se concentre sur l’évolution spatio-temporelle de la chimie dans les régions HII hypercompact et ultracompact avec des PDRs internes aussi bien que dans les coeurs chauds moléculaires. Le but de cette étude est, premièrement, de comprendre l’impact et les effets sur la chimie du champ de rayonnement, en général très fort dans ces régions. Deuxièmement, le but est d’étudier l’émission de diverses espèces spécifiques aux régions HII HC/UC et de comparer cette émission à celle des CCMs, où le champ de rayonnement UV n’a pas d’influence car il est immédiatement atténué par le milieu. En fin de compte nous voulons déterminer l’âge d’une région donnée en utilisant la chimie associée au transfert radiatif. Pour étudier ces stades transitoires de la formation des étoiles massives, nous utilisons le code astrochimique Saptarsy optimisé et amélioré pendant cette thèse de doctorat. Saptarsy est un code gaz-grain calculant l’évolution spatio-temporelle d’abondances relatives. Il est basé sur l’approche des équations des taux de réactions et utilise le réseau chimique OSU (Université de l’État de l’Ohio) mis à jour. De plus, Saptarsy est couplé au code de transfert radiatif RADMC-3D via un programme, basé sur le langage Python, nommé Pandora. Ceci est fait afin d’obtenir des spectres synthétiques directement comparables avec des observations en utilisant l’évolution spatio-temporelle détaillée des abondances chimiques.En plus de la comparaison entre un modèle de région HII HC/UC avec un modèle de CCM, nous obtenons des modèles pour des tailles différentes de régions HII, pour plusieurs densités au front d’ionisation et pour deux profils de densité. Nous étudions les abondances qui dépendent de manière critique des conditions initiales et nous explorons aussi l’importance de l’émission venant de l’enveloppe pour diverses espèces chimiques. Nous constatons que parmi la douzaine d’espèces que nous avons étudiées seulement quatre d’entre elles sont spécifiques à la phase de région HII ou à la phase de coeur chaud. Ces espèces sont C+ et O pour la première phase et CH3OH et H218O pour la deuxième phase. Cependant, un plus grand nombre d’espèces pourrait être utilisées pour étudier et identifier ces phases
Conditions leading to the formation of high-mass stars are still under investigation but an evolutionary scenario has been proposed: As a cold pre-stellar core collapses under gravitational force, the medium warms up and enters the hot molecular core (HMC) phase. The forming central proto-star accretes materials, increasing its mass and luminosity and eventually it becomes sufficiently evolved to emit UV photons which irradiate the surrounding environment forming a hyper compact (HC) and then a ultracompact (UC) HII region. At this stage, a very dense and very thin internal photon-dominated region (PDR) forms between the HII region and the molecular core.Information on the chemistry allows to trace the physical processes occurring in these different phases of star formation. Therefore, chemistry also allows the determination of the evolutionary stage of astrophysical objects through the use of chemical models including the time evolution of the temperature and radiation field. So far, few studies have investigated internal PDRs and only in the presence of outflows cavities. Thus, these unique regions around HC/UCHII regions remain to be examined thoroughly.My PhD thesis focuses on the spatio-temporal chemical evolution in HC/UC HII regions with internal PDRs as well as in HMCs. The purpose of this study is first to understand the impact and effects of the radiation field, usually very strong in these regions, on the chemistry. Secondly, the goal is to study the emission of various tracers of HC/UCHII regions and compare it with HMCs models, where the UV radiation field does not impact the region as it is immediately attenuated by the medium. Ultimately we want to determine the age of a given region using chemistry in combination with radiative transfer. To investigate these transient phases of massive star formation, we use the astrochemical code Saptarsy optimized and improved during this PhD thesis. Saptarsy is a gas-grain code computing the spatio-temporal evolution of relative abundances. It is based on the rate equation approach and uses an updated Ohio State University (OSU) chemical network. Moreover, Saptarsy works along with the radiative transfer code RADMC-3D via a Python based program named Pandora. This is done in order to obtain synthetic spectra directly comparable to observations using the detailed spatio-temporal evolution of species abundances.In addition to comparing a HC/UCHII region to a HMC model, we obtain models for different sizes of HII regions, for various densities at the ionization front and for two different density profiles. We investigate the critical dependance of the abundances on the initial conditions and we also explore the importance of the emission coming from the envelope for various species. We find that among the dozen of molecules and atoms we have studied only four of them trace the UC/HCHII region phase or the HMC phase. They are C+ and O for the first and CH3OH and H218O for the second phase. However, more species could be studied to probe and identify these phases
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Al-Edhari, Ali Jaber. "Complex organic molecules in solar-type star forming regions." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY048/document.

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Le but de la présente thèse est l'étude de la compléxité moléculaire dans les régions de formation stellaires. Cette thèse s'axe sur deux classes de molécule aux caractéristiques prébiotiques : les molécules organiques complexes et les cyanopolyynes.Dans ce contexte, j'ai analysé des données d'un seul échantillon de relevés spec- traux en exploitant des codes de transfert radiatif à l'équilibre thermodynamique local (LTE) et/ou non-LTE pour deux sources : une proto-étoile de type solaire dans un environnement calme (IRAS 16293-2422) et un proto-ama constitué de proto-étoile de type solaire (OMC2-FIR4).L'objectif est de trouver des similar- ités et des différences entre ces deux cas.J'ai utilisé des données issu de deux relevés spectraux : TIMASSS (The IRAS16293-2422 Millimeter And Submilimeter Spectral Survey) réalisés en 2011 (Caux et al. 2011), et ASAI(Astrochemical Surveys At IRAM) réalisés pen- dant la période 2013-2015 (eg Lopez-Sepulcre et al.2015). J'ai extrais les lignes (identification et intensité intégrée) en utilisant le paquet disponible publique- ment : CASSIS (Centre d'Analyse Scientifique de Spectres Infrarouges et Sub- millimetrique). Pour finir, j'ai utilisé le paquet GRAPES (GRenoble Analysis of Protostellar Envelope Spectral) afin de modéliser la distribution spectrale énergétique de ligne (SLED) des molécules détectées, mais aussi afin d'estimer leurs abondances à travers l'envelope de IRAS16293 et du coeur chaud OMC2- FIR4.Les principaux résultats de la thèse sont :1. Le premier recensement complet des molecules organiques complexes (COMs) dans IRAS162932. La première détéction de COMs dans l'enveloppe froide d'une proto-étoile de type solaire (IRAS16293-2422) supportant l'idée qu'un méchanisme de formation, relativement efficace pour les COMs détectées, doit exister en phase gazeuse froide.3. La découverte d'une fine corrélation entre le diméthyle-éther (DME) et le méthyle-formate (MF) suggère une relation mère fille entre ces deux espèces.4. La detection de formamide, espèce avec un très fort potentiel prébiotique, dans plusieurs protoétoiles incluant IRAS16293-2422 et OMC2-FIR4.5. Le recensement complet des cyanopolyynes dans IRAS16293 et OMC2- FIR4 avec la détection de HC3N, HC5N, DC3N et pour OMC2-FIR4: le C13 isotopologue du HC3N cyanopolyynes.Ces résultats sont le sujet principal de deux publications (Jaber et al.2014, ApJ; Lopez-Sepulcre, Jaber et al.2015,MNRAS), un article accepté (Jaber et al., A & A) et un article à soumettre (Jaber et al. A & A)
The present PhD thesis goal is the study of the molecular complexity in solar type star forming regions. It specifically focuses on two classes of molecules with a pre-biotic value, the complex organic molecules and the cyanopolyynes.At this scope, I analyzed data from single-dish spectral surveys by means of non-LTE or/and non-LTE radiative transfer codes in two sources, a solar type protostar in an isolated and quiet environment (IRAS16293-2422) and a proto-cluster of solar type protostars (OMC2-FIR4). The goal is to find similarities and differences between these two cases.I used data from two spectra surveys: TIMASSS (The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey), which has been carried out in 2011 (Caux et al. 2011), and ASAI (Astrochemical Surveys At IRAM), which has been carried out in 2013-2015 (e.g. Lopez-Sepulcre et al. 2015).I extracted the lines (identification and integrated intensity) by means of the publicly available package CASSIS (Centre dAnalyse Scientifique de Spectres Infrarouges et Submillimtriques).Finally, I used the package GRAPES (GRenoble Analysis of Protostellar Envelope Spectra) to model the Spectral Line Energy Distribution (SLED) of the detected molecules, and to estimate their abundance across the envelope and hot corino of IRAS16293-2422 and OMC2-FIR4, respectively.The major results of the thesis are:1) The first full census of complex organic molecules (COMs) in IRAS16293-2422;2) The first detection of COMs in the cold envelope of a solar type protostar (IRAS16293-2422), supporting the idea that a relatively efficient formation mechanism for the detected COMs must exist in the cold gas phase;3) The discovery of a tight correlation between the dimethyl ether (DME) and methyl format (MF), suggesting a mother-daughter relationship;4) The detection of formamide, a species with a very high pre-biotic value, in several protostars, included IRAS16293-2422 and OMC2-FIR4;5) The full census of the cyanopolyynes in IRAS16293-2422 and OMC2-FIR4, with the detection of HC3N and HC5N, DC3N and, for OMC2-FIR4, the 13C isotopologue of HC3N cyanopolyynes.These results are the focus of two published articles (Jaber et al. 2014, ApJ; Lopez-Sepulcre, Jaber et al. 2015, MNRAS), one accepted article (Jaber et al., A&A) and a final article to be submitted (Jaber et al., A&A)
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Vidal, Thomas. "Revisiting the chemistry of star formation." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0151/document.

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Les études astrochimiques de la formation stellaire sont particulièrement importantes pour la compréhension de l'évolution de l'Univers, du milieu interstellaire diffus à la formation des systèmes stellaires. Les récentes avancées en matière de modélisation chimique permettent d'apporter de nouveaux résultats sur le processus de formation stellaire et les structures mises en jeu. L'objectif de ma thèse était donc d'apporter un regard neuf sur la chimie de la formation stellaire en utilisant les récentes avancées sur le modèle chimique Nautilus. J'ai pour cela étudié l'évolution de la chimie du soufre durant la formation stellaire pour tenter d'apporter de nouvelles réponses au problème de déplétion du soufre. J'ai d'abord effectué une révision du réseau chimique soufré et étudié son effet sur la modélisation du soufre dans les nuages denses. En comparant aux observations, j'ai montré que le modèle textsc{Nautilus} était capable de reproduire les abondances des espèces soufrées dans les nuages denses en utilisant comme abondance élémentaire de soufre son abondance cosmique. Ce résultat m'a permis d'apporter de nouveaux indices sur les reservoirs de soufre dans ces objets. Puis j'ai effectué une étude complète de la chimie du souffre dans les coeurs chauds en me concentrant sur les effets sur la chimie de la composition pre-effondrement. J'ai également étudié les conséquences des différentes simplifications couramment faites pour la modélisation des coeurs chauds. Mes résultats montrent que la composition pre-effondrement est un paramètre majeur de l'évolution chimique des coeurs chauds, fournissant de nouveaux indices pour expliquer la variété de compositions en espèces soufrées observée dans ces objets. De plus, ma recherche a mis en évidence la nécessité d'uniformiser les modèles de chimie utilisés pour les coeurs chauds. Enfin, j'ai développé une méthode efficace pour inverser les paramètres initiaux d'effondrement de nuages denses en me basant sur une base de données de modèles physico-chimiques d'effondrement, ainsi que sur l'observation d'enveloppes de protoétoiles de Classe 0. A partir d'un échantillon de 12 sources, j'ai pu en déduire des probabilités concernant les possibles paramètres initiaux d'effondrement de la formation d'étoiles de faible masse
Astrochemical studies of star formation are of particular interest because they provide a better understanding of how the chemical composition of the Universe has evolved, from the diffuse interstellar medium to the formation of stellar systems and the life they can shelter. Recent advances in chemical modeling, and particularly a better understanding of grains chemistry, now allow to bring new hints on the chemistry of the star formation process, as well as the structures it involves. In that context, the objective of my thesis was to give a new look at the chemistry of star formation using the recent enhancements of the Nautilus chemical model. To that aim, I focused on the sulphur chemistry throughout star formation, from its evolution in dark clouds to hot cores and corinos, attempting to tackle the sulphur depletion problem. I first carried out a review of the sulphur chemical network before studying its effects on the modeling of sulphur in dark clouds. By comparison with observations, I showed that the textsc{Nautilus} chemical model was the first able to reproduce the abundances of S-bearing species in dark clouds using as elemental abundance of sulphur its cosmic one. This result allowed me to bring new insights on the reservoirs of sulphur in dark clouds. I then conducted an extensive study of sulphur chemistry in hot cores and corinos, focusing on the effects of their pre-collapse compositions on the evolution of their chemistries. I also studied the consequences of the use of the common simplifications made on hot core models. My results show that the pre-collapse composition is a key parameter for the evolution of hot cores which could explain the variety of sulphur composition observed in such objects. Moreover, I highlighted the importance of standardizing the chemical modeling of hot cores in astrochemical studies. For my last study, I developed an efficient method for the derivation of the initial parameters of collapse of dark clouds via the use of a physico-chemical database of collapse models, and comparison with observations of Class 0 protostars. From this method, and based on a sample of 12 sources, I was able to derive probabilities on the possible initial parameters of collapse of low-mass star formation
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Ospina-Zamudio, Juan David. "Complexité chimique des protoétoiles de masse intermédiaire : une étude de Cep E-mm." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY013/document.

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Les étoiles de masse intermédiaire (2M⊙ ≤ M ≤ 10M⊙) sont parmi les sources dominantes du champ interstellaire FUV dans la Galaxie. Elles régulent les phases du milieu interstellaire et l’ensemble des processus de formation stellaire galactique. Alors que les protoétoiles de type solaire et massives ont été et continuent à faire l’objet de nombreuses études, la formation des étoiles intermédiaires a été relativement peu étudiée. Leur structure physique, composition chimique et leur richesse moléculaire sont un domaine à explorer.L’objectif de ma thèse est d’obtenir un recensement détaillé et aussi complète que possible des propriétés physico-chimiques d’une protoétoile isolée de masse intermédiaire. Notre choix s’est porté sur Cep E-mm (100 L⊙).J’ai pour cela complété un relevé spectral de l’émission moléculaire dans les bandes (sub)millimétriques entre 72 et 350 GHz avec le télescope de 30m de l’IRAM. La sensibilité des observations a permis d’identifier la présence de nombreuses molécules complexes organiques (COMs) dans l’enveloppe de la protoétoile, mais aussi, plusieurs espèces moléculaires inhabituelles dans le jet généré par la protoétoile. Des observations complémentaires avec le télescope de 30m ont permis de cartographier l’émission moléculaire à grande échelle (20’’ à 11’’ ; 15000 à 8000 UA). En parallèle, des cartes interférométriques de l’émission moléculaire entre 86 – 90 GHz et 216 – 220 GHz ont été obtenues avec l’interféromètre de l’IRAM (NOEMA) à 1.4’’ (1000 UA) de résolution angulaire. Ces observations m’ont permis d’obtenir une première description de la distribution de l’émission moléculaire au sein de l’enveloppe, des grandes échelles, dans les parties extérieures de l’enveloppe étendue, aux petites échelles dans la région d’un hot corino. Les études présentées ici ont suivi un travail méticuleux de réduction et d’analyse des données, single-dish et interférométriques. Plus précisément, j’ai identifié et séparé les contributions à l’émission détectée dans le lobe du télescope de 30m de l’IRAM des différentes régions physiques du cœur protostellaire. De ce fait, j’ai identifié et caractérisé quatre composantes physiques qui diffèrent par leurs propriétés spectroscopiques et leurs conditions d’excitation : l’enveloppe étendue, le hot corino, le flot bipolaire basse vitesse et le jet à haute vitesse. Enfin, l’anisotropie de la distribution de brillance du flot et du jet bipolaire ne peut pas être modélisée par l’approche ‘’classique’’ d’une source gaussienne. J’ai développé des outils spécifiques semi-analytiques pour calculer de manière approchée, et plus raisonnable, le couplage entre le lobe du télescope et la source
Intermediate-mass stars (2 M⊙ ≤ M ≤ 10 M⊙) are among the dominant sources of FUV interstellar field in the Galaxy. They regulate the phases of interstellar medium and the whole process of galactic star formation. While solar-type and massive protostars have been and continue to be the subject of many studies, the formation of intermediate stars has been relatively little studied. Their physical structure, chemical composition and molecular richness are still a subject to explore.The aim of my thesis is to obtain a detailed census, as complete as possible ,of the physical and chemical structure of an isolated intermediate-mass protostar: Cep E-mm (100 L⊙).I have completed a spectral survey of the molecular emission in the (sub)millimetre bands between 72 and 350 GHz with IRAM 30m telescope. The sensitivity of the observations made it possible to identify the presence of numerous complex organic molecules (COMs) in the protostar envelope, but also several unusual molecular species in the protostellar jet. Additionally, further observations with the IRAM 30m telescope made it possible to map the molecular emission at large scale (20’’ to 11’’; 15000 to 8000 AU). In parallel, interferometric maps of the molecular emission between 86 – 90 GHz and 216 – 220 GHz were obtained with NOEMA, the IRAM interferometer, at 1.4’’ (1000 AU) of angular resolution. These observations allowed me to obtain the distribution of molecular emission within the source, from large scales in the outer parts of the extended envelope, to the small scales in the hot corino region. The single-dish and interferometric observations were reduced and analysed in a meticulous manner. More precisely, I identified and separated the molecular emission contribution from the different physical regions as observed with the IRAM 30m telescope. I have identified and characterized fours physical components that differ in their spectroscopic properties and excitation conditions: the extended envelope, the hot corino, the bipolar outflow and the high-velocity jet. Finally, the anisotropy of the brightness distribution from the outflow system cannot be modelled by the “classical” Gaussian approach. I have developed specific tools to estimate, in a semi-analytical manner, the coupling between the telescope lobe and the source
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Fechtenbaum, Sarah. "Conditions initiales de la formation des étoiles massives : Astrochimie de la protoétoile CygX-N63." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0204/document.

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La naissance des étoiles massives est aujourd’hui encore mal comprise. En particulier, les conditions initiales de leur formation restent largement inconnues. Pour éclairer cette question, nous avons réalisé un relevé spectral complet non biaisé avec le télescope 30 m de l’IRAM vers la protoétoile massive CygX-N63 (M ~ 58 M◦ et L~ 340 L◦). Nous avons mis en évidence une complexité moléculaire significative avec plus de 40 espèces. L’ion CF+ est observé pour la première fois dans une protoétoile. Une possible première détection de l’espèce prébiotique CH2NH dans une protoétoile est aussi proposée, ainsi qu’une première détection de DOCO+. Cette étude spectroscopique, accompagnée d’observations interférométriques avec le Plateau de Bure, permet de séparer la contribution des différentes régions : enveloppe froide, région tiède, région de type hot core et flot bipolaire. L’enveloppe est constituée d’une grande quantité de gaz froid peu évolué, offrant un potentiel important pour la compréhension des phases précoces de la formation stellaire massive et compatible avec un scénario d’effondrement monolithique. La modélisation chimique montre que la chimie de ce gaz est encore hors équilibre, malgré sa haute densité, et confirme la jeunesse de la protoétoile avec un âge chimique de seulement ~ 1000 ans. N63 est un précurseur de hot core plutôt qu’un hot corino massif. Il serait donc possible de distinguer, grâce à des diagnostics chimiques évolutifs, les précurseurs d’étoiles massives des protoétoiles de masse faible ou ntermédiaire
High-mass star formation is still poorly understood. In particular the initial conditions of their formation are unknown. To explore this question, a complete unbiased spectral survey was conducted with the IRAM 30 m telescope toward the massive protostar CygX-N63 (M~58 M◦ and L~ 340 L◦). A significant molecular complexity is found, with more than 40 species. The ion CF+ is observed for the first time in a protostar. A possible first detection of the prebiotic species CH2NH in a protostar and a first detection of DOCO+ are proposed. This spectroscopic study, along with Plateau de Bure interferometric observations, allows us to separate the contribution of different regions : cold envelope, lukewarm region, hot corelike region and outflow. The envelope contains large amounts of cold and young gas, which gives us the opportunity to better understand the early phases of massive star formation. The chemical modeling shows that the chemistry is still out of equilibrium, despite its high density, and confirms the youth of the protostar with a chemical age of ~ 1000 years. N63 is a hot core precursor rather than a massive hot corino. The use of chemical diagnostics of the evolution would then allow to distinguish massive star precursors from low-mass or intermediate-mass protostars
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Rimmer, Paul Brandon. "The Chemical Impact of Physical Conditions in the Interstellar Medium." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331086619.

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Tabone, Benoît. "L'origine des jets protostellaires à l'ère d'ALMA : de la modélisation aux observations." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEO024/document.

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L’extraction du moment cinétique au sein des disques protostellaires est le processus clé qui détermine la masse finale accrétée par une étoile, ainsi que les conditions de formation de son cortège planétaire. Il a été proposé que les jets protostellaires pourraient jouer un rôle essentiel dans cette extraction, via un processus magnétohydrodynamique (MHD). L’objectif principal de ce travail de thèse est de mettre à profit le gain révolutionnaire en résolution et en sensibilité apporté par l’interféromètre submillimétrique ALMA afin de clarifier le processus d’accrétion-éjection à l’œuvre dans les protoétoiles. Cette pro- blématique est abordée selon trois axes complémentaires i) confrontation des modèles théoriques de vent de disque MHD à la dynamique du jet de HH212 observé par ALMA à haute résolution angulaire. Je présente la découverte de signatures de rotation en SO/SO2 dans le jet qui, avec la dynamique de SiO, sont cohérentes avec un vent de disque MHD lancé entre 0.05 et 40au. ii) étude analytique et numérique de l’impact de la variabilité d’un jet rapide pulsant sur un vent de disque. J’identifie des signatures observationnelles de la présence d’un vent de disque à partir de l’étude morphologique et cinématique des coquilles de choc d’étrave. iii) signatures chimiques d’un jet lancé en deçà de la région de sublimation des poussières (∼ 0.2 au). Je montre que malgré la forte irradiation du jet et l’absence de poussière, des molécules telles que SiO ou CO peuvent se former efficace- ment à partir d’une faible fraction de H2. Ce scénario pourra être confronté aux futures observations JWST
The question of angular momentum extraction from protoplanetary disks (hereafter PPDs) is fundamental in understanding the accretion process in young stars and the formation conditions of planets. Pioneering semi-analytical work, followed by a growing body of magnetohydrodynamic (MHD) simulations, have shown that when a significant vertical magnetic field is present, MHD disk winds (hereafter MHD-DWs) can develop and ex- tract some or all of the angular momentum flux required for accretion. The aim of this PhD thesis is to exploit the unprecedented capabilities provided by ALMA to clarify the accretion-ejection process in protostars. This goal is achieved following three approaches: 1) comparison of MHD-DW models with the kinematics of HH 212 jet observed by ALMA at high angular resolution. I report the discovery of a rotating SO/SO2 wind consistent with a MHD-DWs launched out to ∼40 au with SiO tracing dust-free streamlines launched from 0.05−0.3 au. 2) Analytical and numerical study of the interaction between a pulsat- ing inner jet embedded in a stationary disk wind. Observational signatures are identified from the morphology and the kinematics of bow-shock shells. 3) Chemical signatures of a jet launched inside the dust sublimation radius (∼ 0.2 au). I show that despite the strong X-FUV field and the absence of dust, molecules like SiO or CO can form efficiently from a small fraction of H2. This scenario will be confronted to JWST observations
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Hincelin, Ugo. "Caractérisation physico-chimique des premières phases de formation des disques protoplanétaires." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14603/document.

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Les étoiles de type solaire se forment par l'effondrement d'un nuage moléculaire, durant lequel la matière s'organise autour de l'étoile en formation sous la forme d'un disque, appelé disque protoplanétaire. Dans ce disque se forment les planètes, comètes et autres objets du système stellaire. La nature de ces objets peut donc avoir un lien avec l'histoire de la matière du disque.J'ai étudié l'évolution chimique et physique de cette matière, du nuage au disque, à l'aide du code de chimie gaz-grain Nautilus.Une étude de sensibilité à divers paramètres du modèle (comme les abondances élémentaires et les paramètres de chimie de surface) a été réalisée. Notamment, la mise à jour des constantes de vitesse et des rapports de branchement des réactions de notre réseau chimique s'est avérée influente sur de nombreux points, comme les abondances de certaines espèces chimiques, et la sensibilité du modèle à ses autres paramètres.Plusieurs modèles physiques d'effondrement ont également été considérés. L'approche la plus complexe et la plus consistante a été d'interfacer notre code de chimie avec le code radiatif magnétohydrodynamique de formation stellaire RAMSES, pour modéliser en trois dimensions l'évolution physique et chimique de la formation d'un jeune disque. Notre étude a démontré que le disque garde une trace de l'histoire passée de la matière, et sa composition chimique est donc sensible aux conditions initiales
Low mass stars, like our Sun, are born from the collapse of a molecular cloud. The matter falls in the center of the cloud, creating a protoplanetary disk surrounding a protostar. Planets and other solar system bodies will be formed in the disk.The chemical composition of the interstellar matter and its evolution during the formation of the disk are important to better understand the formation process of these objects.I studied the chemical and physical evolution of this matter, from the cloud to the disk, using the chemical gas-grain code Nautilus.A sensitivity study to some parameters of the code (such as elemental abundances and parameters of grain surface chemistry) has been done. More particularly, the updates of rate coefficients and branching ratios of the reactions of our chemical network showed their importance, such as on the abundances of some chemical species, and on the code sensitivity to others parameters.Several physical models of collapsing dense core have also been considered. The more complex and solid approach has been to interface our chemical code with the radiation-magneto-hydrodynamic model of stellar formation RAMSES, in order to model in three dimensions the physical and chemical evolution of a young disk formation. Our study showed that the disk keeps imprints of the past history of the matter, and so its chemical composition is sensitive to the initial conditions
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Books on the topic "Star formation, astrochemistry"

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C, Minh Y., and Dishoeck, Ewine Fleur van, 1955-, eds. Astrochemistry : from molecular clouds to planetary systems: Proceedings of the 197th Symposium of the International Astronomical Union held in Sogwipo, Cheju, Korea, 23-27 August 1999. San Francisco, CA: Published on behalf of the International Astronomical Union by Astronomical Society of the Pacific, 2000.

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Introduction to Astrochemistry: Chemical Evolution from Interstellar Clouds to Star and Planet Formation. Springer Japan, 2018.

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Yamamoto, Satoshi (Illustrator). Introduction to Astrochemistry: Chemical Evolution from Interstellar Clouds to Star and Planet Formation. Springer London, Limited, 2017.

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Korea) International Astronomical Union Symposium 1999 (Sogwipo-Si and Ewine F. Van Dishoeck. Astrochemistry: From Molecular Clouds to Planetary Systems. Astronomical Society of the Pacific, 2000.

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Yamamoto, Satoshi (Illustrator). Introduction to Astrochemistry: Chemical Processes in Stars and Planet Formation. Springer Japan, 2017.

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Book chapters on the topic "Star formation, astrochemistry"

1

Rana, N. C., and D. A. Wilkinson. "The Role of Metallicity and H2 in Star Formation in the Galaxy." In Astrochemistry, 323–24. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-4774-0_55.

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Nejad, L. A. M., and D. A. Williams. "The C:O ratio in dark clouds with cyclic star formation." In Astrochemistry of Cosmic Phenomena, 249–50. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2761-5_56.

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"Chemistry and Dust Formation in Circumstellar Regions and Supernovae." In Astrochemistry, 129–57. The Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/9781839163968-00129.

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Dust is an important component of the interstellar gas, but it isn't formed in interstellar clouds. It is made in some particular and much denser regions associated with stars, and dust formation follows a period of extensive chemistry in those regions. We describe chemistry and dust formation in two types of region that are believed to make the most significant contributions to dust in the Milky Way. The first regions are the envelopes of fairly cool modest stars (these stars are of about solar mass); these envelopes develop towards the final stages of the stellar evolution. Chemistry, nucleation and then dust deposition may occur in these envelopes, and the amount of dust produced may be sufficient to extinguish the light of the star itself. Newly-formed dust is ultimately driven away from the star by radiation pressure and mixes with pre-existing interstellar dust. The second type of location in which dust is formed is in the explosions that end the lives of much more massive stars; the supernovae. These highly energetic explosions eject large amounts of material from the star, and – unlikely though it may seem – conditions may become favourable for chemistry and for nuclei to form, on which solid dust grains may then be deposited. We discuss the chemistry that leads to nucleation and grain growth in both these scenarios.
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"Conclusions." In Astrochemistry, 227–41. The Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/9781839163968-00227.

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The chemical richness of the Milky Way and other galaxies can be explained by a combination of gas phase reactions together with reactions on the surfaces of dust grains and reactions in ices deposited on those grains. Molecules and dust grains play important roles within galaxies, affecting their physical evolution by driving star and planet formation and modifying the content of the interstellar medium. We show that the difficulties (expressed in Chapter 1) of creating extensive chemistry in the apparently hostile environments of the Milky Way and other galaxies can be readily overcome. Star and planet formation provide locations in which a remarkably rich range of organic molecules can form; these species include a number of amino acids that may form the building blocks of RNA and DNA. This result, confirmed by many laboratory experiments, lends support to the concept of abiogenesis – the origin of life as a consequence of reactions in non-living matter. However, the necessary intervening steps are not yet understood.
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"Interstellar Chemistry, Astrobiology, and the Origin of Life." In Astrochemistry, 185–226. The Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/9781839163968-00185.

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We examine the idea that life may have arisen as a consequence of chemistry occurring in non-living (abiotic) matter, a concept known as abiogenesis. We describe how the formation of stars and planets may provide locations favourable for abiogenesis, and we discuss the chemical and mineralogical diversity in various regions of the solar system. Using evidence from many relevant laboratory experiments we discuss the suitability of these regions for abiogenesis. The difficulties associated with proceeding from a rich chemistry of organic molecules to a chemistry organized and controlled by RNA and DNA are described. There is still much to discover.
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"Surface Chemistry on Interstellar Dust Grains." In Astrochemistry, 158–70. The Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/9781839163968-00158.

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The presence of dust in the interstellar medium was discovered because of the obscuration it causes of the light of distant stars. That obscuration also shields the interiors of interstellar clouds from the destructive effects of starlight and encourages chemistry to develop there. However, dust contributes to interstellar chemistry in other ways, too. In this chapter, we describe the role of dust in enabling surface chemistry to take place in interstellar clouds. This surface chemistry is of greatest importance in the case of molecular hydrogen formation, because H2 plays a seminal role in almost all of interstellar chemistry (as seen in Chapters 4 and 5, particularly). Theoretical and experimental evidence supporting the production of H2 and some other species in surface chemistry is described in this chapter.
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Conference papers on the topic "Star formation, astrochemistry"

1

Hincelin, Ugo, Kenji Furuya, Yuri Aikawa, Tatiana Vasyunina, Qiang Chang, and Eric Herbst. "MODELING OF ASTROCHEMISTRY DURING STAR FORMATION." In 69th International Symposium on Molecular Spectroscopy. Urbana, Illinois: University of Illinois at Urbana-Champaign, 2014. http://dx.doi.org/10.15278/isms.2014.mf09.

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2

Herbst, E. "Gas-Grain Models of Low-Mass Star Formation." In ASTROCHEMISTRY: From Laboratory Studies to Astronomical Observations. AIP, 2006. http://dx.doi.org/10.1063/1.2359564.

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