A5038818756- Astrophysics and Star Formation Studies
- Molecular Spectroscopy and Structure
- Atmospheric Ozone and Climate
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Advanced Chemical Physics Studies
- Spectroscopy and Laser Applications
- Chemical Thermodynamics and Molecular Structure
- Atmospheric chemistry and aerosols
- Advanced Combustion Engine Technologies
- Atomic and Molecular Physics
- Phase Equilibria and Thermodynamics
- Astrophysical Phenomena and Observations
- Planetary Science and Exploration
- Catalysis and Oxidation Reactions
- Fluid Dynamics and Turbulent Flows
- Water Quality Monitoring and Analysis
- High-pressure geophysics and materials
- Scientific Measurement and Uncertainty Evaluation
- Thermal Expansion and Ionic Conductivity
- Molecular spectroscopy and chirality
Ames Research Center
2017-2024
Search for Extraterrestrial Intelligence
2021-2024
Laboratoire d'Astrophysique de Bordeaux
2016-2017
Université de Bordeaux
2015-2017
Centre National de la Recherche Scientifique
2014-2017
Observatoire de Paris
2013
Chemical models used to study the chemical composition of gas and ices in interstellar medium are based on a network reactions associated rate coefficients. These coefficients partially compiled from data literature, when available. We present this paper kida.uva.2014, new updated version kida.uva public gas-phase first released 2012. In addition description many specific updates, we illustrate changes predicted abundances molecules for cold dense cloud conditions as compared with results...
We present an extended version of the two-phase gas–grain code nautilus to three-phase modelling gas and grain chemistry cold cores. In this model, both mantle surface are considered as chemically active. also take into account competition among reaction, diffusion evaporation. The model predictions confronted ice observations in envelope low-mass massive young stellar objects well towards background stars. Modelled gas-phase abundances compared species observed TMC-1 (CP) L134N dark clouds....
Sulphur-bearing species are often used to probe the physical structure of star forming regions interstellar medium, but chemistry sulphur in these is still poorly understood.In dark clouds, supposed be depleted under a form which unknown despite numerous observations and chemical modeling studies that have been performed.In order improve chemistry, we propose an enhancement network using experimental theoretical literature.We test effect updated on outputs three phases gas-grain model for...
Recent observations have revealed the existence of complex organic molecules (COMs) in cold dense cores and pre-stellar cores. The presence these such conditions is not well understood remains a matter debate since previously proposed 'warm-up' scenario cannot explain observations. In this paper, we study effect Eley–Rideal induced reaction mechanisms gas-phase carbon atoms with main ice components dust grains on formation COMs regions. Based recent experiments, use low value for chemical...
The H3+ molecule has been detected in many lines of sight within the central molecular zone (CMZ) with exceptionally large column densities and unusual excitation properties compared to diffuse local clouds. detection (3,3) metastable level suggested be signature warm gas CMZ. We use Meudon PDR code re-examine relationship between density cosmic-ray ionization rate, $ζ$, up values $ζ$. study impact various mechanisms that can excite its state. produce grids models exploring different...
Ionized carbon is the main gas-phase reservoir of in neutral diffuse interstellar medium and its 158 micron fine structure transition [CII] most important cooling line (ISM). We combine absorption emission spectroscopy to gain an improved understanding physical conditions different phases ISM. present high resolution spectra obtained with Herschel/HIFI instrument towards bright dust continuum sources regions Galactic plane, probing simultaneously gas along sight background high-mass star...
Abstract We study the effects of grain surface reactions on chemistry protoplanetary disks where gas, ice layers, and icy mantles dust grains are considered as three distinct phases. Gas-phase is found to be mainly driven by photoreactions temperature gradients. The disk interior has chemical regions: (i) inner midplane with low far-UV (FUV) fluxes warm (≳15 K) that lead formation complex organic molecules, (ii) outer higher FUV from interstellar medium cold hydrogenation dominate, (iii) a...
Abstract We present an ACA search for [C i ] 1–0 emission at 492 GHz toward large T Tauri disks (gas radii ≳ 200 au) in the ∼1–3 Myr-old Lupus star-forming region. Combined with Atacama Large Millimeter/submillimeter Array 12 m archival data IM Lup, we report detections six out of 10 sources, thus doubling known disks. also identify four Keplerian double-peaked profiles and demonstrate that fluxes correlate 13 CO, C 18 O, CO(2–1) fluxes, as well gas disk outer radius measured from latter...
A wide variety of molecules have recently been detected in the Horsehead nebula photodissociation region (PDR) suggesting that: (i) gas-phase and grain chemistries should both contribute to formation organic molecules, (ii) far-ultraviolet (FUV) photodesorption may explain release into gas phase surface species. In order tackle these specific problems more generally better constrain chemical structure types environments we present a study gas-grain chemistry. To do so used 1D astrochemical...
Deuterated species are unique and powerful tools in astronomy since they can probe the physical conditions, chemistry, ionization level of various astrophysical media. Recent observations several deuterated along with some their spin isomeric forms have rekindled interest for more accurate studies on deuterium fractionation. This paper presents first publicly available chemical network multiply chemistry implemented latest state-of-the-art gas-grain code `NAUTILUS'. D/H ratios all observed...
The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU$_{69}$) has been largely undisturbed since its formation. We study surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through radiation of simple molecules. Water was not detected. This indicates hydrogenation carbon monoxide-rich and/ or energetic processing methane condensed on water grains in cold, edge early...
Abstract We present JWST NIRSpec spectroimaging observations of jets from four edge-on protoplanetary disks that exhibit clear signatures MHD disk winds. Bipolar are detected and spatially resolved in over 30 shock-excited forbidden lines, multiple Paschen Brackett series lines atomic hydrogen, the high-energy excitation line helium (1.083 μ m). This is brightest jet tracer toward HH FS TauB, which also asymmetric intensity between their red- blueshifted lobes all tracers, including [Fe ii ]...
Many astrochemical models of observed CO isotopologue line emission, earlier considered a good proxy measure H$_2$ and hence disk gas mass, favor large deviations in the carbon oxygen phase abundances argue that severe depletion makes it poor mass tracer. Here, we show C$^{18}$O emission is an effective despite its complex chemistry, possibly better tracer than HD. Our are able to reproduce from recent ALMA surveys TW Hya within factor $\sim 2-3$ using characteristic interstellar medium...
Abstract Methyl isocyanate (CH3NCO) is one of the important complex organic molecules detected on comet 67P/Churyumov–Gerasimenko by Rosetta’s Philae lander. It was also in hot cores around high-mass protostars along with a recent detection solar-type protostar IRAS 16293−2422. We propose here gas-grain chemical model to form CH3NCO after reviewing various formation pathways quantum computations. have used nautilus three-phase compare observed abundances Our clearly indicates ice phase origin CH3NCO.
Abstract The ketenyl radical (HCCO) has recently been discovered in two cold dense clouds with a non-negligible abundance of few 10−11 (compared to H2). Until now, no chemical network able reproduce this observation. We propose here scheme that can HCCO abundances together HCO, H2CCO and CH3CHO the dark Lupus-1A L486. main formation pathway for is OH + CCH → H reaction as suggested by Agúndez et al. but much larger rate coefficient than used current models. Since never studied experimentally...
Protoplanetary disks are the target of many chemical studies (both observational and theoretical) as they contain building material for planets. Their large vertical radial gradients in density temperature make them challenging objects models. In outer part these disks, densities low temperatures provide a particular environment where binding species onto dust grains can be very efficient affect gas-phase composition. We attempt to quantify what extent abundance profiles integrated column...
Molecular oxygen has been the subject of many observational searches as chemical models predicted it to be a reservoir oxygen. Although detected in two regions interstellar medium, its rarity is challenge for astrochemical models. In this paper, we have combined physical conditions computed with smoothed particle hydrodynamics (SPH) simulations our full gas-grain model Nautilus, study O2 abundance material forming cold cores. We thus follow evolution gas and ices parcels from diffuse dense...
Aims. We study the effect of large scale dynamics on molecular composition dense interstellar medium during transition between diffuse to clouds. Methods. followed formation clouds (on sub-parsec scales) through at galac- tic scales. used results from smoothed particle hydrodynamics (SPH) simulations which we extracted physical parameters that are as inputs for our full gas-grain chemical model. In these simulations, evolution matter is ~50 Myr. The warm low-density gas flows into spiral...
Aims: Interstellar molecules form early in the evolutionary sequence of interstellar material that eventually forms stars and planets. To understand this sequence, it is important to characterize chemical composition its first steps. Methods: In paper, we present result a 2 3 mm survey five cold clumps identified by Planck mission. We carried out radiative transfer analysis on detected lines order put some constraints physical conditions within cores molecular column densities. also...
Abstract CO is one of the most abundant molecules in protoplanetary disks, and optically thin emission from its isotopologues has been detected many them. However, several past works have argued that reproducing relatively low requires a very disk mass or significant depletion. Here, we present Python code, DiskMINT , which includes gas density temperature structures are both consistent with thermal pressure gradient, isotope-selective chemistry, conversion into 2 ice on grain surfaces. The...
We present a study of the elemental depletion in interstellar medium. combined results Galatic model describing gas physical conditions during formation dense cores with full-gas-grain chemical model. During transition between diffuse and medium, reservoirs elements, initially atomic gas, are gradually depleted on dust grains (with phase neutralisation for those which ions). This process becomes efficient when density is larger than 100~cm$^{-3}$. If material goes back into conditions, these...
The effect of H$_2$ ro-vibrational excitation on the chemistry protoplanetary disks is studied using a framework that solves for disk physical and chemical structure includes detailed calculation level populations. Chemistry with ro-vibrationally excited found to be important formation several commonly observed species in this work demonstrates need accurately treat PDR if we are make inferences state during planet epochs. This even more critical molecules like C$_2$H, CN or HCN used infer...
Abstract Asymptotic giant branch stars create a rich inventory of molecules in their envelopes as they lose mass during later stages evolution. These cannot survive the conditions interstellar space, where are exposed to ultraviolet photons radiation field. As result, daughter ones injected into and halo those is predicted exist around cool evolved stars. The most abundant molecule other than H 2 CO, which dissociates C that rapidly ionized + star optically thin We develop specific...