LSST: from Science Drivers to Reference Design and Anticipated Data Products

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta<+34.5^\circ$, and will be imaged multiple times in six bands, $ugrizy$, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg$^2$ region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to $r\sim27.5$. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

Isotopie de l'eau dans la nature — L'eau à la surface du globe

La composition isotopique de l'eau est influencée par les transformations physicochimiques qu'elle subit au cours de son cycle. Ces variations isotopiques fournissent de nombreuses informations sur des phénomènes météorologiques ou hydrologiques variés. Les auteurs montrent, à l'aide d'exemples précis, comment l'étude de ces variations peut aider à la compréhension et à l'interprétation des phénomènes fondamentaux qui les produisent

Oxydation isotopique du mercure par l'oxygène moléculaire sous l'influence de la radiation 2 357 Å

L'étude de l’oxydation du mercure dans les mélanges Hg + O2 et Hg + O2 + butadiène soumis aux photons de longueur 2 537 Å provenant d’une lampe à mercure monoisotopique (202Hg) nous a amené à considérer deux modes de désactivations possibles du mercure Hg 6(3P1) par l’oxygène. Le mode le plus important est le transfert direct de l’énergie à la molécule d’oxygène; le deuxième mode conduit à la formation d’un complexe excité.1er mode :Hg 6 (3[math]2e mode :[math]Le complexe excité [math] en réagissant sur le butadiène permet d’obtenir un composé de mercure fortement enrichi en isotope 202Hg. Les résultats obtenus montrent que la valeur de la section efficace de formation du complexe [math] est de l’ordre de 0,25 Å2

Fractionnement isotopique au cours de la distillation de l’eau

Le facteur de fractionnement isotopique au cours de la distillation de l’eau a été déterminé dans le domaine de température compris entre le point triple et le point critique.Les résultats obtenus ont été comparés à ceux calculés par l’intermédiaire de la règle de la moyenne géométrie. Des écarts ont été observés

Oxydation photochimique du mercure et sélectivité isotopique

L'oxydation de la vapeur de mercure par différents réactifs, stimulée par la radiation de longueur d'onde 2 537 Å produite par une lampe sans électrode à mercure 202, a été étudiée en effectuant, d'une part le dosage de la quantité d'oxyde de mercure formé, d'autre part l'analyse isotopique de ce mercure.Les expériences ont porté, entre autres, sur des mélanges de mercure, vapeur d'eau, oxygène et butadiène.On a mis en évidence que deux types d'oxydation distincts coexistent. L'un est isotopiquement sélectif, l'autre, qui est bloqué par le butadiène, ne l'est pas.En outre, les résultats semblent montrer que le premier stade de la réaction est la formation d'un état associé excité, tel que [HgO2]* ou [HgH2O]*

Electroweak measurements in electron–positron collisions at w-boson-pair energies at lep

Contains fulltext : 121524.pdf (preprint version ) (Open Access

LSST: From science drivers to reference design and anticipated data products

We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the solar system, exploring the transient optical sky, and mapping the Milky Way. LSST will be a large, wide-field ground-based system designed to obtain repeated images covering the sky visible from Cerro Pachón in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg2 field of view, a 3.2-gigapixel camera, and six filters (ugrizy) covering the wavelength range 320–1050 nm. The project is in the construction phase and will begin regular survey operations by 2022. About 90% of the observing time will be devoted to a deep-wide-fast survey mode that will uniformly observe a 18,000 deg2 region about 800 times (summed over all six bands) during the anticipated 10 yr of operations and will yield a co-added map to r ~ 27.5. These data will result in databases including about 32 trillion observations of 20 billion galaxies and a similar number of stars, and they will serve the majority of the primary science programs. The remaining 10% of the observing time will be allocated to special projects such as Very Deep and Very Fast time domain surveys, whose details are currently under discussion. We illustrate how the LSST science drivers led to these choices of system parameters, and we describe the expected data products and their characteristics

Search for Charged Higgs bosons: Combined Results Using LEP Data

The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for pair-produced charged Higgs bosons in the framework of Two Higgs Doublet Models (2HDMs). The data of the four experiments are statistically combined. The results are interpreted within the 2HDM for Type I and Type II benchmark scenarios. No statistically significant excess has been observed when compared to the Standard Model background prediction, and the combined LEP data exclude large regions of the model parameter space. Charged Higgs bosons with mass below 80 GeV/c^2 (Type II scenario) or 72.5 GeV/c^2 (Type I scenario, for pseudo-scalar masses above 12 GeV/c^2) are excluded at the 95% confidence level