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The influence of environment on bacterial co-abundance in the gut microbiomes of healthy human individuals
No full textInternational audienceThe gut microbiome is a complex ecosystem characterized not only by its marginal taxonomic composition but also by its emergent properties. Bacteria develop local interactions to form coherent functional communities, whose effects on health and diseases cannot be predicted from the behavior of individual members. Understanding the factors underlying variability in these communities may therefore provide critical insights on the biological links between the gut microbiome and human phenotypes. Here, we examined the effect of a range of host factors, including demographics, medical history, and dietary habits, on these communities in 938 healthy individuals using MANOCCA, a covariance-based approach developed to address existing limitations. Increased age and smoking were associated with a significant overall decrease in co-abundance, and conversely a higher body mass index was associated with increased co-abundance. At the taxon level, a core of 200 genera were systematically impacted in their co-abundance with other taxa, suggesting a central role in structuring the network. Finally, we demonstrate that our approach offers a powerful framework for prediction purposes, with taxa co-abundance being able to predict the age of participants with an accuracy three-fold higher than a model based on abundance only
Des êtres hybrides et monstrueux comme stimulus cognitif: Densité sémantique, immersion et facilitation de l’apprentissage
No full textInternational audienceL'article (issu d'un travail de doctorat par Mayu IKEDA) explore comment des créatures hybrides et monstrueuses, présentes dans un manuscrit hippiatrique grec du XIVᵉ siècle, agissent comme stimuli cognitifs pour le lecteur. Ces images, à la fois étranges et polysémiques, captent l’attention, renforcent la mémorisation et facilitent la compréhension grâce à leur caractère surprenant. L’étude mobilise des approches issues de la psychologie cognitive (effet de bizarrerie, double codage, réseaux sémantiques) pour montrer que ces figures ne sont pas de simples ornements : elles participent activement à la construction du sens et à l’apprentissage du contenu du manuscrit
JWST reveals the diversity of nuclear obscuring dust in nearby AGN : nuclear isolation of MIRI/MRS data cubes and continuum spectral fitting
No full textInternational audienceWe investigate the capabilities of the mid-infrared instrument (MIRI) of JWST to advance our knowledge of active galactic nucleus (AGN) dust using the spectral fitting technique on an AGN collection of 21 nearby (z<0.05) AGN (7 type-1 and 14 type-2) observations obtained with the medium resolution spectroscopy (MRS) mode. This collection includes publicly available AGN and data from the collaboration of Galactic Activity, Torus, and Outflow Survey (GATOS). We developed a tool named MRSPSFisol that decomposes MRS cubes into point-like and extended contributions. We found statistically good fits for 12 targets with current AGN dust models. The model that provides good fits (\rm {\chi ^2/dof< 2}) for these 12 targets assumes a combination of clumpy and smooth distribution of dust in a flare-disc geometry where the dust grain size is a free parameter. Still, two and one AGN statistically prefer the disc wind and the classical clumpy torus model, respectively. However, the currently available models fail to reproduce 40 per cent of the targets, likely due to the extreme silicate features not well reproduced by the models and signatures of water-ice and aliphatic hydrocarbon absorption features in most targets. New models exploring, for instance, new chemistry, are needed to explain the complexity of AGN dust continuum emission observed by JWST
Virgo Filaments. V. Disrupting the Baryon Cycle in the NGC 5364 Galaxy Group
No full textInternational audienceThe Virgo Filament Survey (VFS) is a comprehensive study of galaxies that reside in the extended filamentary structures surrounding the Virgo Cluster, out to 12 virial radii. The primary goal is to characterize all of the dominant baryonic components within galaxies and to understand whether and how they are affected by the filament environment. A key constituent of VFS is a narrowband Hα imaging survey of over 600 galaxies, VFS-Hα. The Hα images reveal detailed, resolved maps of the ionized gas and massive star formation. This imaging is particularly powerful as a probe of environmentally induced quenching because different physical processes affect the spatial distribution of star formation in different ways. In this paper, we present the first results from the VFS-Hα for the NGC 5364 group, a low-mass system located at the western edge of the Virgo III filament. We combine Hα imaging with resolved H I observations from MeerKAT for eight group members. These galaxies exhibit peculiar morphologies, including strong distortions in the stars and the gas, truncated H I and Hα disks, H I tails, extraplanar Hα emission, and off-center Hα emission. These signatures are suggestive of environmental processing such as tidal interactions, ram pressure stripping, and starvation. We quantify the role of ram pressure stripping expected in this group, and find that it can explain the cases of H I tails and truncated Hα for all but one of the disk-dominated galaxies. Our observations indicate that multiple physical mechanisms are disrupting the baryon cycle in these group galaxies
PHIBSS : Searching for Molecular Gas Outflows in Star-forming Galaxies at z = 0.5–2.6
No full textInternational audienceWe present an analysis of millimeter CO observations to search for and quantify signatures of molecular gas outflows. We exploit the large sample of 0.5 < z < 2.6 galaxies observed as part of the PHIBSS1/2 surveys with the IRAM Plateau de Bure interferometer, focusing on the 154 typical massive star-forming galaxies with CO detections (mainly CO(3–2), but including also CO(2–1) and CO(6–5)) at signal-to-noise ratio (SNR) > 1.5 and available properties (stellar mass, star formation rate or SFR, size) from ancillary data. None of the individual spectra exhibit a compelling signature of CO outflow emission, even at high SNR > 7. To search for fainter outflow signatures, we carry out an analysis of stacked spectra, including the full sample, as well as subsets, split in terms of stellar mass, redshift, inclination, offset in SFR from the main sequence, and active galactic nuclei activity. None of the physically motivated subsamples shows any outflow signature. We report a tentative detection in a subset statistically designed to maximize outflow signatures. We derive upper limits on molecular gas outflow rate and mass loading factors η based on our results and find η ≤ 2.2–35.4, depending on the subsample. Much deeper CO data and observations of alternative tracers are needed to decisively constrain the importance of the cold molecular gas component of outflows relative to other gas phases
Molecular gas in cool-core brightest cluster galaxies at z ≃ 0.4
No full textInternational audienceThe brightest cluster galaxies (BCGs) of today are passive and very massive galaxies at the center of their clusters. They still accrete mass by swallowing companions and flows of cold gas, processes which are regulated by radio-mode active galactic nucleus (AGN) feedback. However, the formation history of BCGs is still a matter of debate. We report new findings based on millimeter observations performed with the Northern Extended Millimeter Array (NOEMA) interferometer mapping the cold molecular gas (CO) that feeds the star formation of distant BCGs. We selected three sources among the strongest cool-core BCGs at intermediate redshifts ( z ≃ 0.4), namely, RX 1532, MACS 1447, and CHIPS 1911. Previous unresolved millimeter observations and multi-wavelength analyses have shown that they are among the most star forming (SFR ≃ 100 M ⊙ /yr) and gas rich ( M H 2 ≃ 10 11 M ⊙ ) BCGs at intermediate redshifts. The selected sources are thus caught in a phase of rapid mass assembly, which makes them ideal targets for high-resolution observations of their molecular gas. We find that all three BCGs show point-like and steep-spectrum continuum emission at millimeter wavelengths, with a spectral slope of α = 0.6, which we interpret as being optically thin synchrotron emission from the AGN. By combining our NOEMA intensity and velocity maps with archival deep optical/infrared images from the Hubble Space Telescope , we unambiguously detected in situ star formation, filaments of accreting cold gas likely regulated by AGN feedback, a disturbed morphology associated with tidal tails of molecular gas, and gas compression and tails originating from the stripping of gas. While effective condensation of the intracluster medium is required to explain the large molecular gas reservoirs, the BCGs exhibit a broad variety of environment-driven mechanisms responsible for the processing of their cold gas: flows of cooling gas (RX 1532), ram pressure or sloshing of the intracluster medium (MACS 1447), and galactic tides (CHIPS 1911). This study thus provides new insights into the physical mechanisms responsible for the mass assembly of galaxies hosting AGN at the center of clusters
Temporalités de la ville en mutation. Une étude comparative des pratiques socio-culturelles et spatiales à Hailar et Oulan-Bator
No full textInternational audienceCette présentation à deux voix explore les transformations des espaces de vie et de circulation à Hailar (Chine) et à Oulan-Bator (Mongolie). En prenant pour point de départ des récits de vie que nous avons récoltés séparément ces dernières années dans ces deux villes, nous nous interrogerons sur la manière dont les Mongols façonnent certains quartiers urbains dans un contexte d’urbanisation rapide. Comment les Mongols mettent-ils à profit divers modes d’occupation et d’appropriation d’espaces urbains en constante mutation ? Quelles sont les stratégies individuelles et/ou collectives ainsi que les pratiques socio-culturelles et spatiales mobilisées pour tirer parti de ces villes ? À Hailar, comment les Mongols s’approprient-ils des microcosmes urbains dans des espaces numériquement dominés par les Chinois ? À Oulan-Bator, comment les Mongols s’approprient-ils des microcosmes urbains dans des espaces créés sous l’influence de l’urbanisation néolibérale ? Au-delà des politiques de développement urbain menées différemment de part et d’autre de la frontière sino-mongole, existe-il des points communs ou au contraire des divergences dans la manière dont les Mongols appréhendent la ville ? À travers ces divers questionnements fondés sur une démarche comparative, nous nous interrogerons plus généralement sur les urbanités contemporaines et futures dans le monde mongol urbai
