Characterizing filaments in regions of high-mass star formation: High-resolution submilimeter imaging of the massive star-forming complex NGC 6334 with ArTeMiS

Context. Herschel observations of nearby molecular clouds suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. The observations support a picture of low-mass star formation according to which filaments of ~0.1 pc width form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and then prestellar cores arise from gravitational fragmentation of the densest filaments. Whether this scenario also applies to regions of high-mass star formation is an open question, in part because the resolution of Herschel is insufficient to resolve the inner width of filaments in the nearest regions of massive star formation. Aims. In an effort to characterize the inner width of filaments in high-mass star-forming regions, we imaged the central part of the NGC 6334 complex at a resolution higher by a factor of >3 than Herschel at 350 μm. Methods. We used the large-format bolometer camera ArTéMiS on the APEX telescope and combined the high-resolution ArTéMiS data at 350 μm with Herschel/HOBYS data at 70–500 μm to ensure good sensitivity to a broad range of spatial scales. This allowed us to study the structure of the main narrow filament of the complex with a resolution of 8″ or <0.07 pc at d ~ 1.7 kpc. Results. Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ~500 M⊙/pc to ~2000 M⊙/pc over nearly 10 pc. It also demonstrates for the first time that its inner width remains as narrow as W ~ 0.15 ± 0.05 pc all along the filament length, within a factor of <2 of the characteristic 0.1 pc value found with Herschel for lower-mass filaments in the Gould Belt. Conclusions. While it is not completely clear whether the NGC 6334 filament will form massive stars in the future, it is two to three orders of magnitude denser than the majority of filaments observed in Gould Belt clouds, and has a very similar inner width. This points to a common physical mechanism for setting the filament width and suggests that some important structural properties of nearby clouds also hold in high-mass star-forming regions

L'hybridation dans le monde végétal

International audienceEn amélioration des plantes le terme hybride correspond à deux notions. Il peut s’agir simplement du résultat du croisement entre deux unités parentales qui peuvent être des clones, des familles ou des populations, de la même espèce, on parle alors d’hybrides intraspécifiques, ou d’espèces différentes, on parle alors d’hybrides interspécifiques. L’hybridation correspond à la réalisation de ce croisement. Mais le terme hybride en amélioration des plantes se réfère en général à un type de variété commercialisé qui est le résultat du croisement contrôlé à grande échelle des deux parents de la variété : il serait alors plus correct de parler dans ce cas de variétés hybrides

Three-dimensional printing of centimetric pieces through multiphoton polymerization process in acrylic resins with nanoparticles

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Reply to comment on the article “Propagation of a lithospheric tear fault (STEP) through the western boundary of the Calabrian accretionary wedge offshore eastern Sicily (Southern Italy)” by Gallais et al., 2013 Tectonophysics

In his Comment, A. Argnani argues that our interpretation of the STEP fault (named STEP-1 fault, in the Comment) is poorly constrained by the seismic data used in Gallais et al. (2013), and he particularly disagrees with our identification north of the Alfeo Seamount. A. Argnani is convinced that the tear fault is expressed by a belt of surface deformation, close to the Malta Escarpment. However, none of the seismic images published by A. Argnani show a crustal scale structure that could be associated with the presence at depth of a lithospheric tear. In that paper we documented the presence of a sub-vertical crustal scale fault, located 50 km east of the Malta Escarpment, with a northward increasing vertical offset (Gallais et al., 2013). The track of this fault towards the north could be extended following the position the fault “F6”, mapped 20 km east of the Malta Escarpment by Nicolich et al. (2000). In fact these authors reported an offset of the crust associated with activity the fault “F6”, suggesting the lithospheric tear at depth at the edge of the Ionian slab is distinct from the Malta Escarpment

Procédé d’impression 3D de pièces en silice par processus de polymérisation multiphotonique

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Etude des interactions entre épis chez le maïs

Trois expériences ont été réalisées pour préciser certains facteurs influençant la dominance de l’épi supérieur. Les facteurs de variation contrôlés ont été le génotype (prolifique ou non), le décalage entre les dates de fécondation de l’épi inférieur et de l’épi supérieur, la nature de la fécondation (autofécondation ou croisement) et l’effeuillage. Le génotype normal n’ayant pas réagi à ces divers traitements, les conclusions sont relatives au génotype prolifique. La fécondation en premier de l’épi inférieur permet de diminuer la dominance de l’épi supérieur : il en résulte une plus grande proportion de plantes à 2 épis et un meilleur équilibre entre les épis. L’effeuillage accentue cette dominance : ce sont les feuilles des épis et celles situées juste au-dessus qui semblent jouer un rôle important. Un effet de la nature de la fécondation a été mis en évidence : par rapport à l’autofécondation, le croisement effectué sur l’épi supérieur semble accentuer la dominance de celui-ci et, inversement, réalisé sur l’épi inférieur il tend à la diminuer. L’ensemble des résultats peut s’interpréter en termes d’offre et de demande de photosynthétats.Three experiments have been carried out to study factors influencing the dominance of the upper ear in maize. The factors tested were : genotype (prolific or not), pollination advantage of upper ear over second ear, type of fertilization (crossing or selfing), and defoliation. Non-prolific genotype was not affected by these treatments so the conclusions relate only to the prolific genotype. Dominance of the upper ear was reduced when it was fertilized after the second ear. This treatment gave a higher percentage of two-eared plants and better balance between the ears. Defoliation increased dominance: the leaves by the ears and those just above appeared most important. Type of fertilization was also observed to have an effect : in comparison to selfing, cross fertilization of the upper ear tends to increase its dominance, while cross fertilization of the second ear tends to decrease it. The results are interpreted in terms of supply and demand of photosynthesatate

Three-dimensional printing of centimetric pieces through multiphoton polymerization process in acrylic resins with nanoparticles

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