Results 1 - 10 of 83
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[en] The C.A.R.M.A. project has for objective the instrumentation of the outlet of the Rhone river with the aim of the consequences evaluation of the floods and storms on the feature evolution of the coast and on the supply in particulates materials of the Gulf of Lion. The societal applications of this project are multiple:development and conservation of the coast, the protection of the shell-fish breeding installations, evolution of fisheries, management of the water quality, as shows the various sources of given co financing (Regions Midi Pyrenees and P.A.C.A., Water Agency Rhone Mediterranean Sea Corsica and European fund of regional development (F.E.D.E.R.). One of the key points of the project is in the synergy between the land measures acquisition and the modelling. This report reports activities of the first phase of the project, its acceptance in the implementation of the instrumentation in Rhone and in its mouth. (N.C.)
[en] In low density, thin plasmas (such as stellar coronae, interstellar medium, intracluster medium) the ionization process is governed by collision between electrons and ions in their ground state. In view of the recent improvements we thought an updating of ionization rates was really needed. The work is based on both experimental data and theoretical works and give separate estimates for the direct and autoionization rates
[en] From soft X ray measurements evidence emerges that a large volume of the local interstellar medium is filled with hot gas. The sky has now been almost entirely scanned in the soft X ray bands. Although the very contribution of a halo or/and large scale galactic components is still debated, it appears that an important part of this soft X ray emission has a local origin. Its thermal nature was strongly supported after X ray lines of some highly stripped ions were observed. This local interstellar medium is likely to have been heated by the energy released in Supernova(e) explosion(s). We review such models and discuss whether they may account for both the observed fluxes in soft X ray bands and the X ray spectral data. Special emphasis is put on the intricacy of the data, which presently makes hopeless a detailed understanding of the hot local interstellar medium. Consistency of such models with key parameters (such as OVI column density) is also studied
[en] Ionization rate coefficients based on several empirical formulae are compared with each other for ions from Hydrogen to Nickel. The coefficients are shown illustratively, and the differences are discussed. (author)
[en] In galaxy clusters, the mass in iron can be considered as directly proportional to the mass in gas. We establised that the mass in gas is linked to the total cluster luminosity in visible matter as Msub(G) is proportional to Lsub(opt)sup(1.6). On the other side, the gas mass seems proportional to the virial mass. We propose that this virial mass is made of star and/or star remnants which produced the iron in the past. The implications of this hypothesis is examined in terms of chemical evolution model of a mass of gas
[en] The Water Management Plan (WMP) prepared for the Rhone Mediterranean Corsica region by the competent French Water Agency in implementation of the 1992 Law on Water regulations, includes provisions for the coastal zone. One of the basic requirements is the implementation of a comprehensive tool to improve both the knowledge and assessment of coastal water quality: the Coastal Mediterranean Monitoring Network. Among the proposed additional surveys, the institution of uniform, permanent monitoring of various pollutants (including radionuclides) has been adopted. In this context, a preliminary study was run using moored shellfish caging devices at more than 80 stations along the French Mediterranean coast. Half of them were selected for radioactivity measurement. This work, undertaken jointly by IFREMER, the Water Agency and IPSN has produced the first outline of the pollution situation for the French Mediterranean coast along the 30 m isobath. The results are compared with those regularly obtained through the IPSN marine observatory and will help re-focus the radionuclide survey. (author)
[en] The difficulty is that the observed source is extended with a very low surface brightness (on the order of 1 photon cm-2s-1ster-1). The purpose of this paper is to present a new instrument making use of old classical concepts which combines a high sensitivity and a fine spectral resolution. Valuable observations can be made in 104 seconds
[en] This study presents the Planck 2015 likelihoods, statistical descriptions of the 2-point correlationfunctions of the cosmic microwave background (CMB) temperature and polarization fluctuations that account for relevant uncertainties, both instrumental and astrophysical in nature. They are based on the same hybrid approach used for the previous release, i.e., a pixel-based likelihood at low multipoles (ℓ< 30) and a Gaussian approximation to the distribution of cross-power spectra at higher multipoles. The main improvements are the use of more and better processed data and of Planck polarization information, along with more detailed models of foregrounds and instrumental uncertainties. The increased redundancy brought by more than doubling the amount of data analysed enables further consistency checks and enhanced immunity to systematic effects. It also improves the constraining power of Planck, in particular with regard to small-scale foreground properties. Progress in the modelling of foreground emission enables the retention of a larger fraction of the sky to determine the properties of the CMB, which also contributes to the enhanced precision of the spectra. Improvements in data processing and instrumental modelling further reduce uncertainties. Extensive tests establish the robustness and accuracy of the likelihood results, from temperature alone, from polarization alone, and from their combination. For temperature, we also perform a full likelihood analysis of realistic end-to-end simulations of the instrumental response to the sky, which were fed into the actual data processing pipeline; this does not reveal biases from residual low-level instrumental systematics. Even with the increase in precision and robustness, the ΛCDM cosmological model continues to offer a very good fit to the Planck data. The slope of the primordial scalar fluctuations, n_s, is confirmed smaller than unity at more than 5σ from Planck alone. We further validate the robustness of the likelihood results against specific extensions to the baseline cosmology, which are particularly sensitive to data at high multipoles. For instance, the effective number of neutrino species remains compatible with the canonical value of 3.046. For this first detailed analysis of Planck polarization spectra, we concentrate at high multipoles on the E modes, leaving the analysis of the weaker B modes to future work. At low multipoles we use temperature maps at all Planck frequencies along with a subset of polarization data. These data take advantage of Planck’s wide frequency coverage to improve the separation of CMB and foreground emission. Within the baseline ΛCDM cosmology this requires τ = 0.078 ± 0.019 for the reionization optical depth, which is significantly lower than estimates without the use of high-frequency data for explicit monitoring of dust emission. At high multipoles we detect residual systematic errors in E polarization, typically at the μK"2 level; we therefore choose to retain temperature information alone for high multipoles as the recommended baseline, in particular for testing non-minimal models. Finally and nevertheless, the high-multipole polarization spectra from Planck are already good enough to enable a separate high-precision determination of the parameters of the ΛCDM model, showing consistency with those established independently from temperature information alone.
[en] We have used the Planck all-sky submillimetre and millimetre maps to search for rare sources distinguished by extreme brightness, a few hundred millijanskies, and their potential for being situated at high redshift. These “cold” Planck sources, selected using the High Frequency Instrument (HFI) directly from the maps and from the Planck Catalogue of Compact Sources (PCCS), all satisfy the criterion of having their rest-frame far-infrared peak redshifted to the frequency range 353–857 GHz. This colour-selection favours galaxies in the redshift range z = 2–4, which we consider as cold peaks in the cosmic infrared background. With a 4'.5 beam at the four highest frequencies, our sample is expected to include overdensities of galaxies in groups or clusters, lensed galaxies, and chance line-of-sight projections. In this paper, we perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500μm sources, in comparison to reference SPIRE fields. About 94% of the SPIRE sources in the Planck fields are consistent with being overdensities of galaxies peaking at 350μm, with 3% peaking at 500μm, and none peaking at 250μm. About 3% are candidate lensed systems, all 12 of which have secure spectroscopic confirmations, placing them at redshifts z> 2.2. Only four targets are Galactic cirrus, yielding a success rate in our search strategy for identifying extragalactic sources within the Planck beam of better than 98%. The galaxy overdensities are detected with high significance, half of the sample showing statistical significance above 10σ. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z ≃ 2, assuming a single common dust temperature for the sources of T_d = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4 × 10"1"2L_⊙, yielding star formation rates of typically 700 M_⊙ yr"-"1. If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 × 10"1"3L_⊙, leading to total star formation rates of perhaps 7 × 10"3M_⊙ yr"-"1 per overdensity. Taken together, these sources show the signatures of high-z (z> 2) protoclusters of intensively star-forming galaxies. Finally, all these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-skyPlanck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies.