Insights on the dynamical history of the Fomalhaut system - Investigating the Fom c hypothesis

The eccentric shape of the debris disk observed around Fomalhaut was first attributed to Fom b, a companion detected near the belt inner-edge, but new constraints on its orbit revealed that it is belt-crossing, highly eccentric $(e \sim 0.6-0.9)$, and can hardly account for the shape of the belt. The best scenario to explain this paradox is that there is another massive body in this system, Fom c, which drives the debris disk shape. The resulting planetary system is highly unstable, which hints at a dynamical scenario involving a recent scattering of Fom b on its current orbit, potentially with the putative Fom c. Our goal is to give insights on the probability for Fom b to have been set on its highly eccentric orbit by a close-encounter with the putative Fom c. We aim to study in particular the part played by mean-motion resonances with Fom c, which could have brought Fom b sufficiently close to Fom c for it to be scattered on its current orbit, but also delay this scattering event. Using N-body simulations, we found that the generation of orbits similar to that of Fom b, either in term of dimensions or orientation, is a robust process involving a scattering event and a further secular evolution of inner material with an eccentric massive body such as the putative Fom c. We found in particular that mean-motion resonances can delay scattering events, and thus the production of Fom b-like orbits, on timescales comparable to the age of the system, thus explaining the witnessing of an unstable configuration. We conclude that Fom b probably originated from an inner resonance with Fom c, which is at least Neptune-Saturn size, and was set on its current orbit by a scattering event with Fom c. Since Fom b could not have formed from material in resonance, our scenario also hints at former migration processes in this planetary system

An independent determination of Fomalhaut b's orbit and the dynamical effects on the outer dust belt

The nearby star Fomalhaut harbours a cold, moderately eccentric dust belt with a sharp inner edge near 133 au. A low-mass, common proper motion companion (Fom b), was discovered near the inner edge and was identified as a planet candidate that could account for the belt morphology. However, the most recent orbit determination based on four epochs of astrometry over eight years reveals a highly eccentric orbit that appears to cross the belt in the sky plane projection. We perform here a full orbital determination based on the available astrometric data to independently validate the orbit estimates previously presented. Adopting our values for the orbital elements and their associated uncertainties, we then study the dynamical interaction between the planet and the dust ring, to check whether the proposed disk sculpting scenario by Fom b is plausible. We used a dedicated MCMC code to derive the statistical distributions of the orbital elements of Fom b. Then we used symplectic N-body integration to investigate the dynamics of the dust belt, as perturbed by a single planet. Different attempts were made assuming different masses for Fom b. We also performed a semi-analytical study to explain our results. Our results are in good agreement with others regarding the orbit of Fom b. We find that the orbit is highly eccentric, is close to apsidally aligned with the belt, and has a moderate mutual inclination relative to the belt plane of. If coplanar, this orbit crosses the disk. Our dynamical study then reveals that the observed planet could sculpt a transient belt configuration with a similar eccentricity to what is observed, but it would not be simultaneously apsidally aligned with the planet. This transient configuration only occurs a short time after the planet is placed on such an orbit (assuming an initially circular disk), a time that is inversely proportional to the planet's mass, and that is in any case much less than the 440 Myr age of the star. We constrain how long the observed dust belt could have survived with Fom b on its current orbit, as a function of its possible mass. This analysis leads us to conclude that Fom b is likely to have low mass, that it is unlikely to be responsible for the sculpting of the belt, and that it supports the hypothesis of a more massive, less eccentric planet companion Fom c.Comment: 17 pages, 15 figures, accepted for publication in Astronomy \& Astrophysic

SUGAR. Sustainable Urban Goods Logistics Achieved by Regional and Local Policies. City Logistics Best Practices: a Handbook for Authorities

This publication is one of the main results of the SUGAR project and it is focused on the Best Practices analysis, a tool for the involvement of the community of experts in the emerging field of city logistics. The handbook proposes a quick overview on the project, a detailed collection of best practice synthesis, a synthesis of transferrability issues of such practices and the methodology for applying some of them to different cities and fields

From urban goods transportation to city logistics, which roles for a public transport operator ? : the case of RATP

Le transport de marchandises en ville bien que composante essentielle de la ville a disparu des schémas d'urbanisme et reste secondaire dans les préoccupations des pouvoirs publics. Pourtant le TMV présente de nouveaux enjeux (fonctionnels, environnementaux, économiques...) qui doivent intéresser les acteurs de la ville. La question posée dans cette thèse est "en quoi un opérateur de transports publics urbains peut-il être intéressé par les nouveaux services de logistique urbaine ?". Pour y répondre, un diagnostic sera tout d'abord mené sur le TMV afin de mieux comprendre sa mauvaise organisation puis seront envisagées les nouvelles formes de régulation possibles sur les services de gestion de la voirie, la mise en place d'espaces logistiques urbains et relais-livraisons, le transport de fret et le déplacement des chalandsUrban freight is an essential component of the city, but it disappeared from the scheme of town planning and remains secondary within authorities concerns. However, urban freight presents new stakes (functional, environmental, economic…) which seem interesting for the city actors. The question raised by this study is “how may a public transport operator be interested in new urban logistics services?” To answer it, a diagnosis of urban logistics will be made to better understand its poor organisation. Then the new possible forms of regulation will be considered. They will be related to roadway system, installation of logistic urban spaces and pick-up points, freight transport and customers movin

Du transport de marchandises en ville à la logistique urbaine, quels rôles pour un opérateur de transports publics urbains ? : l'exemple de la RATP

Urban freight is an essential component of the city, but it disappeared from the scheme of town planning and remains secondary within authorities concerns. However, urban freight presents new stakes (functional, environmental, economic…) which seem interesting for the city actors. The question raised by this study is “how may a public transport operator be interested in new urban logistics services?” To answer it, a diagnosis of urban logistics will be made to better understand its poor organisation. Then the new possible forms of regulation will be considered. They will be related to roadway system, installation of logistic urban spaces and pick-up points, freight transport and customers movingLe transport de marchandises en ville bien que composante essentielle de la ville a disparu des schémas d'urbanisme et reste secondaire dans les préoccupations des pouvoirs publics. Pourtant le TMV présente de nouveaux enjeux (fonctionnels, environnementaux, économiques...) qui doivent intéresser les acteurs de la ville. La question posée dans cette thèse est "en quoi un opérateur de transports publics urbains peut-il être intéressé par les nouveaux services de logistique urbaine ?". Pour y répondre, un diagnostic sera tout d'abord mené sur le TMV afin de mieux comprendre sa mauvaise organisation puis seront envisagées les nouvelles formes de régulation possibles sur les services de gestion de la voirie, la mise en place d'espaces logistiques urbains et relais-livraisons, le transport de fret et le déplacement des chaland

Les relais-livraison dans la logistique du e-commerce, l'émergence de deux modèles

Avec le développement très rapide du commerce électronique depuis les années 2002-2003, les consommateurs européens, notamment en France, en Allemagne, au Royaume-Uni et au Benelux, ont vu s'installer près de chez eux un nombre croissant de relais-livraison, en particulier en zones urbaines. Les relais-livraison sont des points de dépose et de collecte à partir desquels les clients de la vente à distance vont récupérer les colis commandés par internet ou par courrier. Ces relais remplacent la livraison à domicile, qui suppose une remise en main propre du colis par le livreur au destinataire. Dans cet article, nous proposons de recenser les expériences récentes de relais-livraison en Europe, en en étudiant les caractéristiques principales ainsi que les facteurs de réussite ou d'échec. Nous comparons en particulier l'émergence très récente des « consignes automatiques » au déploiement plus ancien (mais qui se fait aujourd'hui sous une forme modernisée) des points-colis hébergés dans les commerces de proximité. La présentation détaillée de quatre expériences (E-box, Kiala, Packstation et Cityssimo) nous permet de dresser des conclusions plus précises sur le devenir de ces réseaux

Orbital fitting of Fomalhaut b and subsequent interaction with the dust belt

International audienceFomalhaut harbours a moderately eccentric dust belt with a planet candidate (Fom b) imaged near its inner edge. MCMC-based orbital determination of Fom b shows that the orbit is highly eccentric (e~=0.9), nearly apsidally aligned with the belt. We study the secular interaction between the planet and the dust ring. We show that only if it is a small mass object, Fom b can perturb the belt without destroying it. But Fom b's perturbing action inevitably drives the belt to high eccentricity and apsidal misalignment. This behaviour is due to the planet's high eccentricity. This dynamical outcome contradicts both observations and orbital determination. We conclude that another, more massive and less eccentric planet (Fom c) is required to dynamically control the belt. We show that Fom b is likely to have been formerly trapped in mean-motion resonance with Fom c and that subsequent eccentricity increase caused it to cross Fom c's orbit and to jump on its present day orbit via a scattering event

SUGAR. Sustainable Urban Goods Logistics Achieved by Regional and Local Policies. City Logistics Best Practices: a Handbook for Authorities

This publication is one of the main results of the SUGAR project and it is focused on the Best Practices analysis, a tool for the involvement of the community of experts in the emerging field of city logistics. The handbook proposes a quick overview on the project, a detailed collection of best practice synthesis, a synthesis of transferrability issues of such practices and the methodology for applying some of them to different cities and fields