HAL-INSU
Not a member yet
203706 research outputs found
Sort by
DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
No full textInternational audienceWe present cosmological results from the measurement of baryon acoustic oscillations (BAO) in galaxy, quasar and Lyman- forest tracers from the first year of observations from the Dark Energy Spectroscopic Instrument (DESI), to be released in the DESI Data Release 1. DESI BAO provide robust measurements of the transverse comoving distance and Hubble rate, or their combination, relative to the sound horizon, in seven redshift bins from over 6 million extragalactic objects in the redshift range and eV prior. These neutrino-mass constraints are substantially relaxed in models beyond CDM. [Abridged.
Efficient Quantum Circuits for Non-Unitary and Unitary Diagonal Operators with Space-Time-Accuracy trade-offs
No full textInternational audienceUnitary and non-unitary diagonal operators are fundamental building blocks in quantum algorithms with applications in the resolution of partial differential equations, Hamiltonian simulations, the loading of classical data on quantum computers (quantum state preparation) and many others. In this paper, we introduce a general approach to implement unitary and non-unitary diagonal operators with efficient-adjustable-depth quantum circuits. The depth, i.e. the number of layers of quantum gates of the quantum circuit, is reducible with respect either to the width, i.e. the number of ancilla qubits, or to the accuracy between the implemented operator and the target one. While exact methods have an optimal exponential scaling either in terms of size, i.e. the total number of primitive quantum gates, or width, approximate methods prove to be efficient for the class of diagonal operators depending on smooth, at least differentiable, functions. Our approach is general enough to allow any method for diagonal operators to become adjustable-depth or approximate, decreasing the depth of the circuit by increasing its width or its approximation level. This feature offers flexibility and can match with the hardware limitations in coherence time or cumulative gate error. We illustrate these methods by performing quantum state preparation and non-unitary-real-space simulation of the diffusion equation: an initial Gaussian function is prepared on a set of qubits before being evolved through the non-unitary evolution operator of the diffusion process
Evolution du magmatisme m´esozo¨ıque (240–90 Ma) dans le sud de l’´Equateur et le nord du Perou : avances geodynamiques issus de la petrochronologiedu zircon et de la geochimie des roches
No full textNational audienc
Thermal evolution and formation of supergene mineralization in the El Salvador District, Chile: evidence from geo-thermochronology.
No full textNational audienc
NIRPS and TESS reveal a peculiar system around the M dwarf TOI-756: A transiting sub-Neptune and a cold eccentric giant
No full textInternational audienceContext . The Near InfraRed Planet Searcher (NIRPS) joined HARPS on the 3.6-m ESO telescope at La Silla Observatory in April 2023, dedicating part of its Guaranteed Time Observations (GTO) program to the radial velocity follow-up of TESS planet candidates to confirm and characterize transiting planets around M dwarfs. Aims . We present the “Sub-Neptunes” subprogram of the NIRPS-GTO, aimed at investigating the composition and formation of sub-Neptunes orbiting M dwarfs. We report the first results of this program with the characterization of the TOI-756 system, which consists of TOI-756 b, a transiting sub-Neptune candidate detected by TESS, as well as TOI-756 c, an additional non-transiting planet discovered by NIRPS and HARPS. Methods . We analyzed TESS and ground-based photometry, high-resolution imaging, and high-precision radial velocities (RVs) from NIRPS and HARPS to characterize the two newly discovered planets orbiting TOI-756, as well as to derive the fundamental properties of the host star. A dedicated approach was employed for the NIRPS RV extraction to mitigate telluric contamination, particularly when the star’s systemic velocity was shown to overlap with the barycentric Earth radial velocity. Results . TOI-756 is a M1V-type star with an effective temperature of T eff ~ 3657 K and a super-solar metallicity ([Fe/H]) of 0.20±0.03 dex. TOI-756 b is a 1.24-day period sub-Neptune with a radius of 2.81 ± 0.10 R ⊕ and a mass of 9.8 −1.6 +1.8 M ⊕ . TOI-756 c is a cold eccentric (e c = 0.45 ± 0.01) giant planet orbiting with a period of 149.6 days around its star with a minimum mass of 4.05 ± 0.11 M Jup . Additionally, a linear trend of 146 m s −1 yr −1 is visible in the radial velocities, hinting at a third component, possibly in the planetary or brown dwarf regime. Conclusions . We present the discovery and characterization of the transiting sub-Neptune TOI-756 b and the non-transiting eccentric cold giant TOI-756 c. This system is unique in the exoplanet landscape, standing as the first confirmed example of such a planetary architecture around an M dwarf. With a density of 2.42 ± 0.49 g cm −3 , the inner planet, TOI-756 b, is a volatile-rich sub-Neptune. Assuming a pure H/He envelope, we inferred an atmospheric mass fraction of 0.023 and a core mass fraction of 0.27, which is well constrained by stellar refractory abundances derived from NIRPS spectra. It falls within the still poorly explored radius cliff and at the lower boundary of the Neptune desert, making it a prime target for a future atmospheric characterization with JWST to improve our understanding of this population
A transiting giant planet in orbit around a 0.2-solar-mass host star
No full textInternational audienceAbstract Planet formation models indicate that the formation of giant planets is substantially harder around low-mass stars due to the scaling of protoplanetary disc masses with stellar mass. The discovery of giant planets orbiting such low-mass stars thus imposes strong constraints on giant planet formation processes. Here we report the discovery of a transiting giant planet orbiting a 0.207 ± 0.011 M ⊙ star. The planet, TOI-6894 b, has a mass and radius of M P = 0.168 ± 0.022 M J (53.4 ± 7.1 M ⊕ ) and R P = 0.855 ± 0.022 R J and probably includes 12 ± 2 M ⊕ of metals. The discovery of TOI-6894 b highlights the need for a better understanding of giant planet formation mechanisms and the protoplanetary disc environments in which they occur. The extremely deep transits (17% depth) make TOI-6894 b one of the most accessible exoplanetary giants for atmospheric characterization observations, which will be key for fully interpreting the formation history of this notable system and for the study of atmospheric methane chemistry
Unexpected chemical composition of waters and salts in the Okavango Delta (Botswana)
No full textNational audienc
The multi-dimensional environmental impact of global crop commodities
No full textInternational audienceAbstract Agriculture is one of the leading causes of detrimental environmental impacts, including greenhouse gas emissions, biodiversity loss and depletion of freshwater resources. Such impacts can be assessed by environmental sustainability indices; however, limitations in current indicators necessitate the development of more robust and standardized crop-specific environmental sustainability indices. Here we developed the crop environmental sustainability index (PLANTdex), a spatially explicit index (5 arcmin resolution) quantifying crop production’s environmental impacts. PLANTdex includes globally standardized indicators of environmental impacts assessing water stress and biodiversity loss via five emissions pathways: greenhouse gas emissions, water consumption, land occupation, and nitrogen and phosphorus fertilizer application. We applied PLANTdex to 16 crops, revealing high variability across production system efficiencies, crop types and local context environmental sensitivities. Globally and nationally, no clear correlation emerged between PLANTdex scores and crop production, but stronger correlations were evident at finer spatial scales and for individual crops. Sugar cane showed the strongest negative correlation (low impacts in high-production areas), while oil palm had the strongest positive correlation (high impacts in high-production areas), highlighting the importance of sub-national, crop-specific assessments. PLANTdex’s spatial resolution and crop specificity make it valuable for initiatives such as the Taskforce on Nature-related Financial Disclosures and corporate sustainability strategies
ALMA-JELLY. I. High Resolution CO(2–1) Observations of Ongoing Ram Pressure Stripping in NGC 4858 Reveal Asymmetrical Gas Tail Formation and Fallback
No full textInternational audienceAbstract We present new CO(2–1) observations (resolution ∼1″ = 460 pc) of the Coma cluster jellyfish galaxy NGC 4858 obtained from the ALMA-JELLY large program. Analyzing this data alongside complimentary Subaru H α and Hubble Space Telescope (F600LP / F350LP) observations, we find numerous structural and kinematic features indicative of the effects from strong, inclined ram pressure, including an asymmetric inner gas tail. We estimate a highly inclined disk-wind angle of ϕ DW = 7 5 − 27 + 10 . By subtracting a simple circular velocity model, we find (1): gas clumps that are being accelerated by ram pressure, and (2): signatures of gas clumps that had been previously pushed out of the disk but are now falling inward. We also discuss head-tail morphologies in star complexes within the stellar disk that appear to be ram pressure stripping (RPS)-influenced. Lastly, we compare this galaxy to state-of-the-art galaxy “wind tunnel” simulations. We find that this galaxy is one of the best nearby examples of strong and inclined ram pressure gas stripping, and of gas that is perturbed by ram pressure but not fully stripped and falls back. We emphasize the importance of torques due to ram pressure in highly inclined interactions, which help drive gas inward on the side rotating against the wind, contributing to the formation of asymmetric inner RPS tails
Earth’s past and present mantle oxygen fugacity
No full textInternational audienceOxygen is the most abundant element in Earth’s mantle. Oxygen fugacity (fO2), which quantifies the availability of oxygen to mediate oxidation–reduction reactions, affects important mantle processes, such as depth of melting, extraction of volatiles to the atmosphere, crustal composition and ore body generation. Debate continues over modern and past variations in mantle fO2. In this Review, we compile thermobarometric data from mafic and ultramafic rocks at ridges, back-arcs, and arcs and show that the fO2 of subduction-influenced arc mantle is appreciably higher than the mantle supplying ocean ridges. We review the timing and mechanisms that might transfer redox budget to the arc mantle wedge. A new proxy for the redox-sensitive element vanadium confirms the higher oxidation state of arc mantle and can be used to show there is no conclusive evidence for oxidation of the ambient mantle since the Archaean (2,500–4,000 million years ago). Earlier, in the Hadean magma ocean (>4,000 million years ago), liquid silicate equilibrated with liquid metal alloy while the upper mantle was rapidly oxidized to higher fO2. Future research should focus on how mantle fO2 coevolved with Earth’s primitive atmosphere during core formation, magma ocean crystallization and degassing