Valentine Wakelam

Valentine Wakelam
Laboratoire d'astrophysique de Bordeaux

Dr

About

264
Publications
19,674
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8,317
Citations
Introduction
I obtained an ERC starting grant that started in september 2013. Follow the activities of the group on our web site and blog: http://www.obs.u-bordeaux1.fr/amor/VWakelam/3DICE
Additional affiliations
October 2006 - present
French National Centre for Scientific Research
Position
  • Permanent researcher
October 2006 - October 2016
Laboratoire d'astrophysique de Bordeaux
Position
  • CNRS permanent researcher
January 2005 - September 2006
The Ohio State University
Position
  • PostDoc Position

Publications

Publications (264)
Preprint
Full-text available
The observational counterparts of theoretically predicted first hydrostatic cores (FHSC) have been searched for in the interstellar medium for nearly two decades now. Distinguishing them from other types of more evolved but still embedded objects remains a challenge because these objects have a short lifetime, are small, and embedded in a dense coc...
Article
Context. The sulfur abundance is poorly known in most environments. Yet, deriving the sulfur abundance is key to understanding the evolution of the chemistry from molecular clouds to planetary atmospheres. We present observations of H 2 S 1 10 –1 01 at 168.763 GHz toward the Herbig Ae star AB Aur. Aims. We aim to study the abundance of sulfuretted...
Preprint
The sulfur abundance is poorly known in most environments. Yet, deriving the sulfur abundance is key to understanding the evolution of the chemistry from molecular clouds to planetary atmospheres. We present observations of H$_2$S 110-101 at 168.763 GHz toward the Herbig Ae star AB Aur. We aim to study the abundance of sulfuretted species toward AB...
Article
The Si+SO2 reaction is investigated to verify its impact on the abundances of molecules with astrochemical interest, such as SiS, SiO, SO and others. According to our results Si(3P) and SO2 react barrierlessly yielding only the monoxides SO and SiO as products. No favourable pathway has been found leading to other products, and this reaction should...
Preprint
Full-text available
The Si+SO$_2$ reaction is investigated to verify its impact on the abundances of molecules with astrochemical interest, such as SiS, SiO, SO and others. According to our results Si($^3$P) and SO$_2$ react barrierlessly yielding only the monoxides SO and SiO as products. No favourable pathway has been found leading to other products, and this reacti...
Preprint
Full-text available
In the context of the IRAM 30m Large Program GEMS, we present a study of thioformaldehyde in several starless cores located in star-forming filaments of Taurus, Perseus, and Orion. We investigate the influence of the environmental conditions on the abundances of these molecules in the cores, and the effect of time evolution. We have modelled the ob...
Article
Context. In the context of the IRAM 30 m Large Program Gas phase Elemental abundances in Molecular CloudS (GEMS), we present a study of thioformaldehyde (H 2 CS) and its deuterated versions (HDCS and D 2 CS) in several starless cores located in a selected set of star-forming filaments of Taurus, Perseus, and Orion. These regions have different star...
Preprint
Full-text available
Characterizing the molecular composition of solar-type protostars is useful for improving our understanding of the physico-chemical conditions under which the Sun and its planets formed. In this work, we analyzed the Atacama Large Millimeter/submillimeter Array (ALMA) data of the Protostellar Interferometric Line Survey (PILS), an unbiased spectral...
Article
Full-text available
Characterizing the molecular composition of solar-type protostars is useful for improving our understanding of the physico-chemical conditions under which the Sun and its planets formed. In this work, we analyzed the Atacama Large Millimeter/submillimeter Array (ALMA) data of the Protostellar Interferometric Line Survey (PILS), an unbiased spectral...
Preprint
Full-text available
The reaction between atomic carbon in its ground electronic state, C(3P), and nitrous oxide, N2O, has been studied below room temperature due to its potential importance for astrochemistry, with both species considered to be present at high abundance levels in a range of interstellar environments. On the experimental side, we measured rate constant...
Preprint
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The evolution of star-forming regions and their thermal balance are strongly influenced by their chemical composition, that, in turn, is determined by the physico-chemical processes that govern the transition between the gas phase and the solid state, specifically icy dust grains (e.g., particles adsorption and desorption). Gas-grain and grain-gas...
Article
Full-text available
Context. Methanol, one of the simplest complex organic molecules in the interstellar medium, has been shown to be present and extended in cold environments such as starless cores. Studying the physical conditions at which CH 3 OH starts its efficient formation is important to understand the development of molecular complexity in star-forming region...
Preprint
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Methanol, one of the simplest complex organic molecules in the Interstellar Medium (ISM), has been shown to be present and extended in cold environments such as starless cores. We aim at studying methanol emission across several starless cores and investigate the physical conditions at which methanol starts to be efficiently formed, as well as how...
Article
Full-text available
Context. Grain surface chemistry is fundamental to the composition of protoplanetary disks around young stars. Aims. The temperature of grains depends on their size. We evaluate the impact of this temperature dependence on the disk chemistry. Methods. We modeled a moderately massive disk with 16 different grain sizes. We used the 3D Monte Carlo POL...
Preprint
Full-text available
Silicon monosulfide is an important silicon bearing molecule detected in circumstellar envelopes and star forming regions. Its formation and destruction routes are not well understood, partially due to the lack of a detailed knowledge on the involved reactions and their rate coefficients. In this work we have calculated and modeled the potential en...
Article
Context. The chemical and physical evolution of starless and pre-stellar cores are of paramount importance to understanding the process of star formation. The Taurus Molecular Cloud cores TMC 1-C and TMC 1-CP share similar initial conditions and provide an excellent opportunity to understand the evolution of the pre-stellar core phase. Aims. We inv...
Preprint
The chemical and physical evolution of starless and pre-stellar cores are of paramount importance to understanding the process of star formation. The Taurus Molecular Cloud cores TMC 1-C and TMC 1-CP share similar initial conditions and provide an excellent opportunity to understand the evolution of the pre-stellar core phase. We investigated the e...
Preprint
Full-text available
Under cold conditions in dense cores, gas-phase molecules and atoms are depleted from the gas-phase to the surface of interstellar grains. Considering the time scales and physical conditions within these cores, a portion of these molecules has to be brought back into the gas-phase to explain their observation by milimeter telescopes. We tested the...
Article
Full-text available
Context. Under cold conditions in dense cores, gas-phase molecules and atoms are depleted from the gas-phase to the surface of interstellar grains. Considering the time scales and physical conditions within these cores, a portion of these molecules has to be brought back into the gas-phase to explain their observation by milimeter telescopes. Aims....
Preprint
Grain surface chemistry is key to the composition of protoplanetary disks around young stars. The temperature of grains depends on their size. We evaluate the impact of this temperature dependence on the disk chemistry. We model a moderately massive disk with 16 different grain sizes. We use POLARIS to calculate the dust grain temperatures and the...
Preprint
Full-text available
Rate constants have been measured for the C(3P) + CH3CN reaction between 50 K and 296 K using a continuous-flow supersonic reactor. C(3P) atoms were created by the in-situ pulsed laser photolysis of CBr4 at 266 nm, while the kinetics of C(3P) atom loss were followed by direct vacuum ultra-violet laser induced fluorescence at 115.8 nm. Secondary mea...
Preprint
Full-text available
Aims: Interstellar molecules form early in the evolutionary sequence of interstellar material that eventually forms stars and planets. To understand this evolutionary sequence, it is important to characterize the chemical composition of its first steps. Methods: In this paper, we present the result of a 2 and 3 mm survey of five cold clumps identif...
Preprint
Full-text available
Gas phase Elemental abundances in Molecular CloudS (GEMS) is an IRAM 30m Large Program designed to estimate the S, C, N, and O depletions and gas ionization degree, X(e-), in a set of star-forming filaments of Taurus, Perseus and Orion. Our immediate goal is to build up a complete database of molecular abundances that can serve as an observational...
Article
Gas phase Elemental abundances in Molecular CloudS (GEMS) is an IRAM 30 m Large Program designed to provide estimates of the S, C, N, and O depletions and gas ionization degree, X(e ⁻ ), in a selected set of star-forming filaments of Taurus, Perseus, and Orion. Our immediate goal is to build up a complete and large database of molecular abundances...
Article
Full-text available
Aims. Interstellar molecules form early in the evolutionary sequence of interstellar material that eventually forms stars and planets. To understand this evolutionary sequence, it is important to characterize the chemical composition of its first steps. Methods. In this paper, we present the result of a 2 and 3 mm survey of five cold clumps identif...
Article
Context. Carbon monosulphide (CS) is among the most abundant gas-phase S-bearing molecules in cold dark molecular clouds. It is easily observable with several transitions in the millimeter wavelength range, and has been widely used as a tracer of the gas density in the interstellar medium in our Galaxy and external galaxies. However, chemical model...
Preprint
Full-text available
CS is among the most abundant gas-phase S-bearing molecules in cold dark molecular clouds. It is easily observable with several transitions in the millimeter wavelength range, and has been widely used as a tracer of the gas density in the interstellar medium in our Galaxy and external galaxies. Chemical models fail to account for the observed CS ab...
Preprint
Full-text available
Nitrogen-bearing molecules display variable isotopic fractionation levels in different astronomical environments such as in the interstellar medium or in the Solar System. Models of interstellar chemistry are unable to induce nitrogen fraction in cold molecular clouds as exchange reactions for 15N are mostly inefficient. Here, we developed a new ga...
Article
Full-text available
Context. The chemical composition of protoplanetary disks is expected to impact the composition of the forming planets. Characterizing the diversity of chemical composition in disks and the physicochemical factors that lead to this diversity is consequently of high interest. Aims. The aim of this study is to investigate the chemical evolution from...
Article
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This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of th...
Article
Full-text available
This paper presents an overview of the current status of the Virtual Atomic and Molecular Data Centre (VAMDC) e-infrastructure, including the current status of the VAMDC-connected (or to be connected) databases, updates on the latest technological development within the infrastructure and a presentation of some application tools that make use of th...
Preprint
(Abridged) The aim of this study is to investigate the chemical evolution from the prestellar phase to the formation of the disk, and to determine the impact that the chemical composition of the cold and dense core has on the final composition of the disk. We performed 3D nonideal magneto-hydrodynamic (MHD) simulations of a dense core collapse usin...
Article
Carbon containing molecules in cold molecular clouds show various levels of isotopic fractionation through multiple observations. To understand such effects, we have developed a new gas-grain chemical model with updated 13C fractionation reactions (also including the corresponding reactions for 15 N, 18O, and 34S). For chemical ages typical of dens...
Preprint
Full-text available
Measuring isotopic ratios is a sensitive technique used to obtain information on stellar nucleosynthesis and chemical evolution. We present measurements of the carbon and sulphur abundances in the interstellar medium of the central region of our Galaxy. The selected targets are the +50km/s Cloud and several l.o.s. clouds towards Sgr B2(N). Towards...
Article
Full-text available
We present a study of the elemental depletion in the interstellar medium. We combined the results of a Galactic model describing the gas physical conditions during the formation of dense cores with a full-gas-grain chemical model. During the transition between diffuse and dense medium, the reservoirs of elements, initially atomic in the gas, are gr...
Article
The current generation of (sub)mm-telescopes has allowed molecular line emission to become a major tool for studying the physical, kinematic, and chemical properties of extragalactic systems, yet exploiting these observations requires a detailed understanding of where emission lines originate within the Milky Way. In this paper, we present 60 arcse...
Article
Full-text available
Context. Measuring isotopic ratios is a sensitive technique used to obtain information on stellar nucleosynthesis and chemical evolution. Aims. We present measurements of the carbon and sulphur abundances in the interstellar medium of the central region of our Galaxy. The selected targets are the +50 km s ⁻¹ Cloud and several line-of-sight clouds t...
Preprint
Full-text available
Carbon containing molecules in cold molecular clouds show various levels of isotopic fractionation through multiple observations. To understand such effects, we have developed a new gas-grain chemical model with updated 13C fractionation reactions (also including the corresponding reactions for 15N, 18O and 34S). For chemical ages typical of dense...
Preprint
Full-text available
We present a study of the elemental depletion in the interstellar medium. We combined the results of a Galatic model describing the gas physical conditions during the formation of dense cores with a full-gas-grain chemical model. During the transition between diffuse and dense medium, the reservoirs of elements, initially atomic in the gas, are gra...
Preprint
The current generation of (sub)mm-telescopes has allowed molecular line emission to become a major tool for studying the physical, kinematic, and chemical properties of extragalactic systems, yet exploiting these observations requires a detailed understanding of where emission lines originate within the Milky Way. In this paper, we present 60$^{\pr...
Article
Context. Complex organic molecules with three carbon atoms are found in the earliest stages of star formation. In particular, propenal (C 2 H 3 CHO) is a species of interest due to its implication in the formation of more complex species and even biotic molecules. Aims. This study aims to search for the presence of C 2 H 3 CHO and other three-carbo...
Article
Full-text available
Context. Complex organic molecules with three carbon atoms are found in the earliest stages of star formation. In particular, propenal (C 2 H 3 CHO) is a species of interest due to its implication in the formation of more complex species and even biotic molecules. Aims. This study aims to search for the presence of C 2 H 3 CHO and other three-carbo...
Preprint
Complex organic molecules with three carbon atoms are found in the earliest stages of star formation. In particular, propenal (C$_2$H$_3$CHO) is a species of interest due to its implication in the formation of more complex species and even biotic molecules. This study aims to search for the presence of C$_2$H$_3$CHO and other three-carbon species s...
Article
Full-text available
Aims. The aim of this work is to provide semi-empirical branching ratios (BRs) for the kinetic databases used in astrochemistry, such as the KInetic Database for Astrochemistry (KIDA). Our work focuses on the CH y ⁽⁺⁾ species ( y = 2–4) excited by cosmic rays (CR), electrons, and photons (UV), or the intermediate excited complexes CH y ⁽⁺⁾ resultin...
Article
Context. Sulphur is one of the most abundant elements in the Universe. Surprisingly, sulphuretted molecules are not as abundant as expected in the interstellar medium and the identity of the main sulphur reservoir is still an open question. Aims. Our goal is to investigate the H 2 S chemistry in dark clouds, as this stable molecule is a potential s...
Preprint
Full-text available
Sulphur is one of the most abundant elements in the Universe. Surprisingly, sulphuretted molecules are not as abundant as expected in the interstellar medium, and the identity of the main sulphur reservoir is still an open question. Our goal is to investigate the H$_{2}$S chemistry in dark clouds, as this stable molecule is a potential sulphur rese...
Article
Full-text available
Molecular oxygen has been the subject of many observational searches as chemical models predicted it to be a reservoir of oxygen. Although it has been detected in two regions of the interstellar medium, its rarity is a challenge for astrochemical models. In this paper, we have combined the physical conditions computed with smoothed particle hydrody...
Article
Full-text available
Context: Sulphur is one of the most abundant elements in the Universe (S/H∼1.3×10 -5 ) and plays a crucial role in biological systems on Earth. The understanding of its chemistry is therefore of major importance. Aims: Our goal is to complete the inventory of S-bearing molecules and their abundances in the prototypical photodissociation region...
Preprint
Full-text available
Aims. Our goal is to complete the inventory of S-bearing molecules and their abundances in the prototypical photodissociation region (PDR) the Horsehead nebula to gain insight into sulphur chemistry in UV irradiated regions. Based on the WHISPER millimeter (mm) line survey, our goal is to provide an improved and more accurate description of sulphur...