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La frontière absente. Études réunies en l’honneur de François de Polignac
No full textInternational audienceÀ l’occasion des soixante-dix ans de François de Polignac, nous sommes réunis autour de ce projet d’édition pour développer des sujets de recherche inspirés de ses publications et de son enseignement à l’École pratique des hautes études. Ce volume prend la forme non pas de mélanges mais d’essais sur des thématiques autour de l’Antiquité grecque, de la structuration de l’espace et des constructions identitaires, combinant des sources archéologiques et textuelles, et propose une réflexion dans le temps et l’espace. Nous voulons ainsi montrer, par des cas d’étude, comment François de Polignac a su aborder les civilisations antiques par une vision aussi précise que large, en intégrant les données sur la longue durée et en évitant d’adopter un modèle interprétatif uniforme dans le processus de la rédaction historique. L’aspect comparatiste s’est révélé important entre des régions et des époques différentes, du monde gréco-romain jusqu’à la Mésopotamie et la Chine. Une partie des textes est consacrée au commentaire de ses travaux dans le but d’expliquer comment ceux-ci nous inspirent et ouvrent des perspectives à d’autres réflexions et recherches
Des sources à saisir : temporalités et usages de sources à la marge
No full textInternational audienceLes sources représentent le support de toute entreprise de recherche en sciences humaines et sociales. Elles désignent l’ensemble des documents sélectionnés par le chercheur qui lui permettent de construire et d’étayer son discours scientifique, en tant qu’ils permettent l’émission d’hypothèses ou qu’ils apparaissent comme des preuves permettant de les confirmer ou de les réfuter. Parmi ces sources, certaines semblent a priori insaisissables ou à la marge du fait de leur nature et des usages particuliers qu’elles supposent. Pourtant, les traces orales, sonores, visuelles, éphémères, rares et uniques nous proposent, pour toutes les périodes historiques, de nouvelles réflexions et interprétations des passés et de la manière dont ils nous parviennent. Ainsi cette journée organisée entre les jeunes chercheurs de l’École nationale des chartes et de l’École pratique des hautes études se propose-t-elle d’interroger ces sources [i]à saisir[/i] au prisme de leurs temporalités multiples, des moyens et des méthodes qu’elles supposent
SS-Men Against Nazism? The Controversial Case of the Mutiny of Villefranche-de-Rouergue (17 September 1943)
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Food, Scarcity and Power in Southeastern Europe during the Second World War
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A sharp view on the small-scale star formation in a remarkable redshift 2.58 spiral galaxy
No full textInternational audienceDuring cosmic noon, galaxies experience intense star formation phases that double the galaxy stellar mass over short time scales. Their morphologies are dominated by compact stellar clumps which are trust to be a major mode of star formation and mass growth during this period. In contrast to HST based studies, JWST observations have revealed that spiral galaxies are already in place at redshift higher than 1.5, with higher than expected incidence of bulges and even bars structures. To capture this rapid evolution phase, we propose NIRSpec/IFU observations of the optical rest-frame of Sp-a2744, a remarkable face-on spiral at z=2.58, detected in the UNCOVER data of the lensing cluster Abell 2744. Homogenous 2D magnification preserves the morphological appearance of this target that shows ~40 clumps, an asymmetric disk, a potential bar and proto-bulge in the making. This galaxy represents a unique laboratory to study the rapid morphological evolution and the star formation cycle close to the peak of star formation history. Recently, ALMA has mapped the giant molecular clouds (GMCs) at resolution comparable to the here requested NIRSPEC/IFU observations. The combination of ALMA, NIRCam, and NIRSpec/IFU will enable us to derive key physical properties (age, SFR, dynamical mass, extinction, electron density, gas pressure, metallicity, ionisation parameters) down to 10s of parsec scales. We will evaluate the effect of stellar feedback on the disruption of their parent GMCs, in setting the integrated star formation efficiency, power the ionised ISM, as well as probe bulge formation in a representative MS galaxy at cosmic noon
Virgo Filaments: III. The gas content of galaxies in filaments as predicted by the GAEA semi-analytic model
No full textInternational audienceGalaxy evolution depends on the environment in which galaxies are located. The various physical processes (ram-pressure stripping, tidal interactions, etc.) that are able to affect the gas content in galaxies have different efficiencies in different environments. In this work, we examine the gas (atomic HI and molecular H2) content of local galaxies inside and outside clusters, groups, and filaments as well as in isolation using a combination of observational and simulated data. We exploited a catalogue of galaxies in the Virgo cluster (including the surrounding filaments and groups) and compared the data against the predictions of the Galaxy Evolution and Assembly (GAEA) semi-analytic model, which has explicit prescriptions for partitioning the cold gas content in its atomic and molecular phases. We extracted from the model both a mock catalogue that mimics the observational biases and one not tailored to observations in order to study the impact of observational limits on the results and predict trends in regimes not covered by the current observations. The observations and simulated data show that galaxies within filaments exhibit intermediate cold gas content between galaxies in clusters and in isolation. The amount of HI is typically more sensitive to the environment than H2 and low-mass galaxies (log10[M⋆/M⊙]< 10) are typically more affected than their massive (log10[M⋆/M⊙]> 10) counterparts. Considering only model data, we identified two distinct populations among filament galaxies present in similar proportions: those simultaneously lying in groups and isolated galaxies. The former has properties more similar to cluster and group galaxies, and the latter is more similar to those of field galaxies. We therefore did not detect the strong effects of filaments themselves on the gas content of galaxies, and we ascribe the results to the presence of groups in filaments
Double, double, toil, and trouble. The tails, bubbles, and knots of the local compact obscured nucleus galaxy NGC 4418
No full textInternational audienceContext. Compact obscured nuclei (CONs) are an extremely obscured (NH2 > 1025 cm−2) class of galaxy nuclei thought to exist in 20-40 per cent of nearby (ultra-)luminous infrared galaxies While they have been proposed to represent a key phase of the active galactic nucleus (AGN) feedback cycle, the nature of these CONs - what powers them, their dynamics, and their impact on the host galaxy - remains unknown. Aims: This work analyses the galaxy-scale optical properties of the local CON NGC 4418 (z = 0.00727). The key aims of the study are to understand the impact of nuclear outflows on the host galaxy and infer the power source of its CON. Through the mapping of the galaxy spectra and kinematics, we seek to identify new structures in NGC 4418 to ultimately reveal more about the CON's history, its impact on the host, and, more generally, the role CONs play in galaxy evolution. Methods: We present new, targeted integral field unit observations of the galaxy with the Multi-Unit Spectroscopic Explorer (MUSE). For the first time, we mapped the ionised and neutral gas components of the galaxy, along with their dynamical structure, to reveal several previously unknown features of the galaxy. Results: We confirm the presence of a previously postulated, blueshifted outflow along the minor axis of NGC 4418. We find this outflow to be decelerating and, for the first time, show it to extend in both directions from the nucleus. We report the discovery of two further outflow structures: a redshifted southern outflow connected to a tail of ionised gas surrounding the galaxy and a blueshifted bubble to the north. In addition to these features, we find the [O III] emission reveals the presence of knots across the galaxy, which are consistent with regions of the galaxy that have been photoionised by an AGN. Conclusions: We identify several new features in NGC 4418, including a bubble structure, a reddened outflow, and [O III] knot structures throughout the galaxy. We additionally confirm the presence of a bilateral blueshifted outflow along the minor axis. Based on the properties of these features, we conclude that the CON in NGC 4418 is most likely powered by AGN activity
Reductive C(sp2)−Si Cross‐Couplings by Catalytic Sodium‐Bromine Exchange
No full textInternational audienceAbstract The metal‐halogen exchange reaction constitutes one of the most important preparative routes towards polar organometallic reagents such as aryllithium or Grignard reagents. However, despite extensive developments over the past eight decades, this fundamental organometallic elementary step has only been exploited stoichiometrically. Against this background, we demonstrate that the sodium‐bromine exchange reaction can be implemented in a catalytic setting as a mean to activate C(sp2)−Br bonds in a transition metal‐free manner en route to the regioselective and general preparation of (hetero)aryl silanes. Simply treating structurally diverse (hetero)aryl bromides with N ‐ tert ‐butyl‐ N’ ‐silyldiazenes (tBu−N=N−Si) as silylating reagents and inexpensive sodium alkoxides as catalytic promoters yields a range of aromatic organosilicon compounds under ambient conditions. Mechanistic studies provide solid evidence for the involvement of tert ‐butyl sodium as the C(sp2)−Br metalating agent
Differential trajectories of the annual reproductive cycle in sheep and cattle from Neolithic to modern times
No full textInternational audienceRegulation of fertility is an important aspect of reproductive control in farm animals which have inherited vestiges of seasonal reproduction from their wild ancestors. Cattle and sheep seem to have followed different paths in this respect. Like the current representatives of their wild ancestor the oriental mouflon, modern sheep under temperate latitudes express a seasonal anoestrus. This has considerable consequences for flock management and product availability. Out-of-season lambing, particularly in breeds with a less profound anoestrus - typically Mediterranean breeds, is nevertheless possible. By contrast, while the last representatives of their wild ancestor, the aurochs, were described as seasonal breeders in the 16th century Poland; and while feral cattle populations in Europe reproduce seasonally, today’s domestic cattle are non-seasonal breeders. The history of these two trajectories is still poorly understood, but recent methodological advances in zooarchaeology allow to go back to their origins. The seasonal cycles recorded in tooth enamel during growth can be reconstructed from oxygen isotope ratios, making it possible to determine the birth seasons in of animals of the past. We will present an overview of the recent results which, on the one hand, demonstrate the existence of autumn lambing as early as the 6th millennium BCE in the western Mediterranean and, on the other hand, the persistence of highly seasoned reproduction in cattle at least until the 4th millennium in continental Europe. The reasons for these different trajectories will be tentatively explained and discussed