A5058783429- Astrophysics and Star Formation Studies
- Atmospheric Ozone and Climate
- Molecular Spectroscopy and Structure
- Spectroscopy and Laser Applications
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Advanced Combustion Engine Technologies
- Calibration and Measurement Techniques
- Markov Chains and Monte Carlo Methods
- Adaptive optics and wavefront sensing
- Characterization and Applications of Magnetic Nanoparticles
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Gaussian Processes and Bayesian Inference
- Ocular and Laser Science Research
- Planetary Science and Exploration
- Advanced Vision and Imaging
- Science and Science Education
- International Relations and Foreign Policy
- Superconducting and THz Device Technology
- Belt and Road Initiative
- Atmospheric and Environmental Gas Dynamics
- Advanced Thermodynamic Systems and Engines
- Astrophysical Phenomena and Observations
National Radio Astronomy Observatory
2024-2025
Institut de Radioastronomie Millimétrique
2020-2024
Orion Corporation (United Kingdom)
2022
Ausonius Institut de Recherche sur l'Antiquité et le Moyen age
2021-2022
Institut de Planétologie et d'Astrophysique de Grenoble
2017-2019
Université Grenoble Alpes
2017-2018
Centre National de la Recherche Scientifique
2017-2018
National Institute for Space Research
2013
Isotopic ratios are keys to understanding the origin and early evolution of solar system in context Galactic nucleosynthesis. The large range measured 14N/15N isotopic reflects distinct reservoirs nitrogen whose origins remain be determined. We have directly a C14N/C15N abundance ratio 323 ± 30 disk orbiting nearby young star TW Hya. This value, which is good agreement with for prestellar cores, likely primary present-day reservoir neighbourhood. These results support models invoking novae...
We use sub-arcsecond resolution ($\sim$0.4$''$) observations with NOEMA at 1.37 mm to study the dust emission and molecular gas of 18 high-mass star-forming regions. combine derived physical chemical properties individual cores in these regions estimate their ages. The temperature structure are determined by fitting H2CO CH3CN line emission. density profiles inferred from continuum visibilities. column densities 11 different species lines XCLASS. Within observed regions, we identify 22...
Context. Massive stars form within dense clumps inside giant molecular clouds (GMCs). Finding appropriate chemical tracers of the gas ( n (H 2 ) > several 10 4 cm −3 or A V 8 mag) and linking their line luminosity with star formation rate is critical importance. Aims. Our aim to determine origin physical conditions HCN-emitting study relation those other molecules. Methods. In context IRAM 30m ORION-B large program, we present 5 deg (~250 pc HCN, HNC, HCO + , CO J =1–0 maps Orion B GMC,...
Context. The availability of large bandwidth receivers for millimeter radio telescopes allows the acquisition position-position-frequency data cubes over a wide field view and broad frequency coverage. These contain much information on physical, chemical, kinematical properties emitting gas. However, their size coupled with inhomogenous signal-to-noise ratio (SNR) are major challenges consistent analysis interpretation.Aims. We search denoising method low SNR regions studied that would allow...
Modern (sub)millimeter interferometers, such as ALMA and NOEMA, offer high angular resolution unprecedented sensitivity. This provides the possibility to characterize morphology of gas dust in distant galaxies. To assess capabilities current software recovering morphologies surface brightness profiles interferometric observations, we tested performance Spergel model for fitting uυ -plane, which has been recently implemented IRAM GILDAS ( uv_fit ). provide an alternative Sérsic profile, with...
Context . Robust radiative transfer techniques are requisite for efficiently extracting the physical and chemical information from molecular rotational lines. Aims We study several hypotheses that enable robust estimations of column densities conditions when fitting one or two transitions per species. extent to which simplifying assumptions aimed at reducing complexity problem introduce estimation biases how detect them. Methods focus on CO HCO + isotopologues analyze maps a 50 square...
The current generation of millimeter (mm) receivers is capable producing cubes 800,000 pixels over 200,000 frequency channels to cover a number square degrees the 3,mm atmospheric window. Estimating physical conditions interstellar medium (ISM) with an astrophysical model on basis such large datasets challenging. Common approaches tend converge local minima and end up poorly reconstructing regions low signal-to-noise ratio (S/N) in most cases. This instrumental revolution thus calls for new...
The origin of the heavily fractionated reservoir nitrogen in comets remains an issue theory their formation and hence solar system. Whether traced by is inherited from interstellar cloud or product processes taking place protostar, protoplanetary disk, unclear. So far, observations isotopic ratios protostars prestellar cores have not securely identified such a owing to intrinsic difficulty direct measurements. In this article, we report detection 5 rotational lines \ce{HC3N}, {including...
CO isotopologue transitions are routinely observed in molecular clouds to probe the column density of gas, elemental ratios carbon and oxygen, trace kinematics environment. We aim at estimating abundances, excitation temperatures, velocity field dispersions three main isotopologues towards a subset Orion B cloud. use Cramer Rao Bound (CRB) technique analyze estimate precision physical parameters framework local-thermodynamic-equilibrium radiative transfer with an additive white Gaussian...
We present well-resolved near-IR and sub-mm analysis of the three highly star-forming massive ($>10^{11}\,\rm M_{\odot}$) galaxies within core RO-1001 galaxy group at $\rm z=2.91$. Each them displays kpc-scale compact star-bursting cores with properties consistent forming bulges, embedded center extended, stellar disks. Surprisingly, disks are unambiguously both quiescent, severely lopsided. Therefore, `outside-in' quenching is ongoing in galaxies. propose an overall scenario which strong...
Abstract Bok globules are small, dense clouds that act as isolated precursors for the formation of single or binary stars. Although recent dust polarization surveys, primarily with Planck, have shown molecular strongly magnetized, significance magnetic fields in has largely been limited to individual case studies, lacking a broader statistical understanding. In this work, we introduce comprehensive optical polarimetric survey 21 globules. Using Gaia and near-IR photometric data, produce...
The ionization fraction plays a key role in the physics and chemistry of neutral interstellar medium, from controlling coupling gas to magnetic field allowing fast ion-neutral reactions that drive chemistry. Most estimations have relied on deuterated species such as DCO+, whose detection is limited dense cores representing an extremely small volume giant molecular clouds they are part of. As large field-of-view hyperspectral maps become available, new tracers may be found. We search for best...
Molecular hydrogen being unobservable in cold molecular clouds, the column density measurements of gas currently rely either on dust emission observation far-IR or star counting. (Sub-)millimeter observations numerous trace molecules are effective from ground based telescopes, but relationships between one line and H2 (NH2) is non-linear sensitive to excitation conditions, optical depths, abundance variations due underlying physico-chemistry. We aim use multi-molecule infer NH2 radio...
Understanding the initial properties of star-forming material and how they affect star formation process is key. From an observational point view, feedback from young high-mass stars on future still poorly constrained. In framework IRAM 30m ORION-B large program, we obtained observations translucent moderately dense gas, which used to analyze kinematics over a field 5 deg^2 around filamentary structures. We ROHSA algorithm decompose de-noise C18O(1-0) 13CO(1-0) signals by taking spatial...
Atoms and molecules have long been thought to be versatile tracers of the cold neutral gas in universe, from high-redshift galaxies star forming regions proto-planetary disks, because their internal degrees freedom bear signature physical conditions where these species reside. However, promise that molecular emission has a strong diagnostic power underlying chemical state is still hampered by difficulty combine sophisticated codes with dynamics. It therefore important 1) acquire...
Bok globules are small, dense clouds that act as isolated precursors for the formation of single or binary stars. Although recent dust polarization surveys, primarily with Planck, have shown molecular strongly magnetized, significance magnetic fields in has largely been limited to individual case studies, lacking a broader statistical understanding. In this work, we introduce comprehensive optical polarimetric survey 21 globules. Using Gaia and near-IR photometric data, produce extinction...
Robust radiative transfer techniques are requisite for efficiently extracting the physical and chemical information from molecular rotational lines.We study several hypotheses that enable robust estimations of column densities conditions when fitting one or two transitions per species. We extent to which simplifying assumptions aimed at reducing complexity problem introduce estimation biases how detect them.We focus on CO HCO+ isotopologues analyze maps a 50 square arcminutes field. used...
Context. Observations of ionic, atomic, or molecular lines are performed to improve our understanding the interstellar medium (ISM). However, potential a line constrain physical conditions ISM is difficult assess quantitatively, because complexity physics. The situation even more complex when trying which combinations most useful. Therefore, observation campaigns usually try observe as many possible for much time possible. Aims. We have searched quantitative statistical criterion evaluate...
Context . Dense and cold molecular cores filaments are surrounded by an envelope of translucent gas. Some the low- J emission lines CO HCO + isotopologues more sensitive to conditions either in environment or dense one because their intensities result from a complex interplay radiative transfer chemical properties these heterogeneous sight (LoSs). Aims We extend our previous single-zone modeling with realistic approach that introduces multiple layers take account possibly varying along LoS....
Dense cold molecular cores/filaments are surrounded by an envelope of translucent gas. Some the low-J emission lines CO and HCO$^+$ isotopologues more sensitive to conditions either in environment or dense one. We propose a cloud model composed three homogeneous slabs gas along each LoS, representing shielded inner layer. IRAM-30m data from ORION-B large program toward Horsehead nebula used demonstrate method's capability. use non-LTE radiative transfer code RADEX line profiles kinetic...
We performed an observational study of the relation between interstellar magnetic field alignment and star formation in twenty (20) sky regions containing Bok Globules. The presence young stellar objects globules is verified by a search infrared sources with spectral energy distribution compatible pre main-sequence star. direction mapped using optical polarimetry. These maps are used to estimate dispersion each region from Gaussian fit, sigma_B. In addition dispersion, we propose new...
This work considers a challenging radio-astronomy inverse problem of physical parameter inference from multispectral observations. The forward model underlying this is computationally expensive numerical simulation. In addition, the observation mixes different sources noise yielding non-concave log-likelihood function. To overcome these issues, we introduce likelihood approximation with controlled error. Given absence ground truth, conducted Markov chain Monte Carlo (MCMC) algorithm to...
We present 5 deg^2 (~250 pc^2) HCN, HNC, HCO+, and CO J=1-0 maps of the Orion B GMC, complemented with existing wide-field [CI] 492 GHz maps, as well new pointed observations rotationally excited H13CN, HN13C lines. detect anomalous HCN hyperfine structure line emission almost everywhere in cloud. About 70% total luminosity arises from gas at A_V < 8 mag. The HCN/CO intensity ratio shows a bimodal behavior an inflection point 3 mag typical translucent UV-illuminated cloud edges. find that...
Modern (sub)millimeter interferometers, such as ALMA and NOEMA, offer high angular resolution unprecedented sensitivity. This provides the possibility to characterize morphology of gas dust in distant galaxies. To assess capabilities current softwares recovering morphologies surface brightness profiles interferometric observations, we test performance Spergel model for fitting $uv$-plane, which has been recently implemented IRAM software GILDAS (uv$\_$fit). provide an alternative Sersic...