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The nested morphology of disk winds from young stars revealed by JWST/NIRSpec observations
No full textInternational audienceRadially extended disk winds could be the key to unlocking how protoplanetary disks accrete and how planets form and migrate. A distinctive characteristic is their nested morphology of velocity and chemistry. Here we report James Webb Space Telescope near-infrared spectrograph spectro-imaging of four young stars with edge-on disks, three of which have already dispersed their natal envelopes. For each source, a fast collimated jet traced by [Fe II] is nested inside a hollow cavity within wider lower-velocity H2. In one case, a hollow structure is also seen in CO ro-vibrational (v = 1 → 0) emission but with a wider opening angle than the H2, and both of those are nested inside an Atacama Large Millimeter Array CO (J = 2 → 1) cone with an even wider opening angle. This nested morphology, even for sources with no envelope, strongly supports theoretical predictions for wind-driven accretion and underscores the need for theoretical work to assess the role of winds in the formation and evolution of planetary systems
Night O<sub>2</sub> (a<sup>1</sup>Δ<sub>g</sub>) airglow spatial distribution and temporal behavior on Venus based on SPICAV IR/VEx nadir dataset
No full textInternational audienceThe infrared O2 (a1Δg) airglow driven by the subsolar to antisolar circulation occurs between two global circulation regimes on Venus: the zonal super-rotation below 90 km and the subsolar to antisolar circulation over 120 km. Here we report the complete global results of SPICAV IR/Venus Express observations of O2 (a1Δg) nightglow from 2006 till the end of the mission in 2014. The spectrometer resolving power of ~1000 at the considered spectral range was the highest among Venus Express instruments, and it was sufficient to resolve O2 (a1Δg) airglow and thermal emission signals. The nadir spectra were fitted to a model representing these two phenomena ensuring robust separation of the thermal emission, and so retrieval of the airglow intensity. Its spatial distribution in the night hemisphere, averaged among 8 years of observations, shows the maximum intensity of 1.4 ± 0.8 MR located at 23H30 of local time and 0–5° N of latitude. A high variability of the airglow was observed. “Bright spots”, i.e., those with an intensity above the global maximum, were observed over a latitude range of 70°S-70°N with the majority occurring around the antisolar point. Lack of imaging capability was an obstacle to track the short-term variations by SPICAV IR. A single observation sequence of 20 days covering neighboring locations exhibits indications of airglow intensity fluctuations with a 5.4-day periodicity. SPICAV IR working period covered the end of the 23rd Solar cycle and the solar activity increase of the 24th Solar cycle. A correlation of the O2 (a1Δg) with the EUV solar flux increase predicted by global circulation model simulations was not found
The thermodynamic structure and large-scale structure filament in MACS J0717.5+3745
No full textInternational audienceWe present the results of Chandra and XMM-Newton X-ray imaging and spatially-resolved spectroscopy, as well as new MUSTANG2 90~GHz observations of the thermal Sunyaev-Zeldovich from MACS J0717.5+3745, an intermediate redshift () and exceptionally massive () Frontier Fields cluster experiencing multiple mergers and hosting an apparent X-ray bright large scale structure filament. Thermodynamical maps are produced from Chandra, XMM-Newton, and ROSAT data using a new method for modelling the astrophysical and instrumental backgrounds. The temperature peak of keV is also the pressure peak of the cluster and closely correlates spatially with the Sunyaev-Zeldovich peak from the MUSTANG2 data. The cluster center hosts shock fronts to the north and south, for which we report lower limits for the shock Mach numbers of and , respectively. Bayesian X-ray Analysis methods were used to disentangle different projected spectral signatures for the filament structure, with Akaike and Bayes criteria being used to select the most appropriate model to describe the various temperature components. We report an X-ray filament temperature of keV and a density , corresponding to an overdensity of 150 relative to the critical density of the Universe. We estimate the hot gas mass of the filament to be , while its total projected weak lensing measured mass is , indicating a hot baryon fraction of 4-10%
Homogeneous Linewidth Behaviour of Narrow Optical Emitters at Sub-kelvin Temperatures
No full textInternational audienceWe explore the properties of ultra-narrow spectral holes in ensembles of solid-state emitters in crystals over a range of sub-kelvin temperatures, with a focus on their potential application in frequency stabilization schemes as an alternative to ultrastable cavities. We investigate how the parameters used to burn the spectral hole impact its shape, and how these factors determine the minimum achievable linewidth. In addition to the stability of the hole's center frequency, the linewidth and contrast play a crucial role in frequency locking. At sub-kelvin temperatures, the temperaturedependent T^7 broadening from two-phonon Raman scattering is expected to be negligible, and the spectral hole's linewidth should therefore remain constant in this interval. We observe however a linear broadening with increasing temperature, highlighting the need for further investigation into the mechanisms governing the linewidth at ultra-low temperatures
DESI 2024 V: Full-Shape Galaxy Clustering from Galaxies and Quasars
No full textInternational audienceWe present the measurements and cosmological implications of the galaxy two-point clustering using over 4.7 million unique galaxy and quasar redshifts in the range $0.
Advancing winter wheat yield anomaly prediction with high-resolution satellite-based gross primary production
No full textInternational audienceWith global food security increasingly threatened by climate variability, accurate crop yield predictions are essential for sustainable agriculture. Winter wheat, with its long growing season influenced by complex climate and management interactions, presents a significant challenge for current predictive models, which often fail under extreme weather conditions despite their complexity and reliance on extensive interactive predictive variables. Here, we employ Harmonized Landsat Sentinel-2 gross primary production (HLS-GPP) data to predict winter wheat yield anomalies across France. HLS-GPP showed strong spatiotemporal correlation with yield anomalies achieving satisfactory accuracy 1 month before harvest and optimal predictions 2 weeks prior. Including rainfall anomalies further enhanced yield anomaly forecasting under extreme weather conditions, where HLS-GPP better predicted significant losses previously unpredicted by national forecasting systems. Our model offers a more efficient wheat yield forecasting tool by minimizing predictive variables and computational demands, offering a practical tool for adaptive food security planning
Flooding increases plant-derived carbon accumulation in soils of aquatic-terrestrial ecotone
No full textInternational audienc
KiDS-Legacy: angular galaxy clustering from deep surveys with complex selection effects
No full textInternational audiencePhotometric galaxy surveys, despite their limited resolution along the line of sight, encode rich information about the large-scale structure (LSS) of the Universe thanks to the large number density and extensive depth of the data. However, the complicated selection effects in wide and deep surveys will potentially cause significant bias in the angular two-point correlation function (2PCF) measured from those surveys. In this paper, we measure the 2PCF from the newly published KiDS-Legacy sample. Given an -band magnitude limit of and survey footprint of deg, it achieves an excellent combination of sky coverage and depth for such a measurement. We find that complex selection effects, primarily induced by varying seeing, introduce over-estimation of the 2PCF by approximately an order of magnitude. To correct for such effects, we apply a machine learning-based method to recover an ``organised random'' (OR) that presents the same selection pattern as the galaxy sample. The basic idea is to find the selection-induced clustering of galaxies using a combination of self-organising maps (SOM) and hierarchical clustering (HC). This unsupervised machine learning method is able to recover complicated selection effects without specifying their functional forms. We validate this ``SOM+HC'' method on mock deep galaxy samples with realistic systematics and selections derived from the KiDS-Legacy catalogue. Using mock data, we demonstrate that the OR delivers unbiased 2PCF cosmological parameter constraints, removing the offset in the galaxy bias parameter that is recovered when adopting uniform randoms. Blinded measurements on the real KiDS-Legacy data show that the corrected 2PCF is robust to the SOM+HC configuration near the optimal setup suggested by the mock tests. Our software is open-source for future usage
Predictions for dispersion measures of fast radio bursts through the epoch of reionization using CoDa II
No full textInternational audienceDispersion measures (DM) of fast radio bursts (FRBs) probe the density of electrons in the intergalactic medium (IGM) along their lines-of-sight, including the average density versus distance to the source and its variations in direction. While previous study focused on low-redshift, FRBs are potentially detectable out to high redshift, where their DMs can, in principle, probe the epoch of reionization (EOR) and its patchiness. We present the first predictions from large-scale, radiation-hydrodynamical simulation of fully-coupled galaxy formation and reionization, using Cosmic Dawn (``CoDa")~II to model the density and ionization fields of the universe down to redshifts through the end of the EOR at . Combining this with an N-body simulation CoDa~II--Dark Matter of the fully-ionized epoch from the EOR to the present, we calculate the mean and standard deviation of FRB DMs as functions of their source redshift. The mean and standard deviation of DM increase with redshift, reaching a plateau by , i.e. well above . The mean-DM asymptote reflects the end of the EOR and its duration. The standard deviation there is , reflecting inhomogeneities of both patchy reionization and density. Inhomogeneities in ionization during the EOR contribute per cent) of this value of from FRBs at redshifts . Current estimates of FRB rates suggest this may be detectable within a few years of observation
Wave-kinetic dynamics of forced-dissipated turbulent internal gravity waves
No full text6 pages, 5 figures, 1 supplementary materialInternational audienceInternal gravity waves are an essential feature of flows stratified media, such as oceans and atmospheres. To investigate their dynamics, we perform simulations of the forced-dissipated kinetic equation describing the evolution of the energy spectrum of weakly nonlinear internal gravity waves. During the early evolution, the three well-known non-local interactions, the Elastic Scattering, the Induced-Diffusion, and the Parametric Sub-Harmonic Instability, together with the Super-Harmonic Instability play a prominent role. In contrast, local interactions are responsible for anisotropic energy cascade on longer time scales. We reveal emergence of a condensate at small horizontal wavevectors that can be interpreted as a pure wave-wave interaction-mediated layering process. We also observe the dynamical formation of an energy spectrum compatible with the Garrett-Munk prediction