Les témoignages du lit de la chambre de la duchesse de Bourbon au Palais-Bourbon et leur présentation au Louvre

Le musée du Louvre conserve un ensemble exceptionnel de tapisseries des Gobelins provenant du décor de la chambre de la duchesse de Bourbon au Palais-Bourbon : une suite de quatre tapisseries murales exécutées d’après des cartons de Maurice Jacques et François Boucher et trois panneaux traditionnellement associés au grand lit à la duchesse qui formait le principal ornement de la pièce. Ces tapisseries furent dispersées à la Révolution puis progressivement réintégrées au sein des collections nationales par des achats s’échelonnant entre 1825 et 1970. Les panneaux du lit ont fait l’objet d’une étude récente en vue de leur exposition dans les salles rénovées du département des Objets d’art. La confrontation avec les cartons de Maurice Jacques, conservés au Mobilier national, et avec les indications fournies par les mémoires et inventaires du xviiie siècle, qui donnent des descriptions assez précises du lit, a permis de reconsidérer leur provenance et de proposer une présentation, fondée sur l’évocation d’un lit de parade, au sein du décor exceptionnel constitué par les boiseries de la chambre de parade de l’hôtel de Chevreuse (Luynes) rue Saint-Dominique.The Louvre today holds an exceptional ensemble of Gobelins tapestries which come from the bed chamber of the Duchess of Bourbon at the Palais-Bourbon. It comprises a series of four wall tapestries executed after the cartoons of Maurice Jacques and François Boucher and three panels traditionally associated with the grand canopy bed which was the principal piece of furniture in this chamber. These tapestries were dispersed at the time of the Revolution then gradually reintegrated into the national collections by purchases between 1825 and 1970. The bed panels have been the object of a recent study in preparation for their exhibition in the Louvre’s renovated rooms devoted to art objects. The comparison with the cartoons by Maurice Jacques, held by the Mobilier national, and with indications given by eighteenth-century texts and inventories give relatively precise descriptions of the bed. This allows for a museum presentation which evokes a bed of state within the exceptional decor made up of the wood panelling of the state bed chamber of the Hôtel de Chevreuse (Luynes) in the rue Saint-Dominique in Paris

Structure formation in a colliding flow: The Herschel view of the Draco nebula

The Draco nebula is a high Galactic latitude interstellar cloud likely to have been formed by the collision of a Galactic halo cloud entering the disk of the Milky Way. Such conditions are ideal to study the formation of cold and dense gas in colliding flows of warm gas. We present Herschel-SPIRE observations that reveal the fragmented structure of the interface between the infalling cloud and the Galactic layer. This front is characterized by a Rayleigh-Taylor instability structure. From the determination of the typical length of the periodic structure (2.2 pc) we estimated the gas kinematic viscosity and the turbulence dissipation scale (0.1 pc) that is compatible with that expected if ambipolar diffusion is the main mechanism of energy dissipation in the WNM. The small-scale structures of the nebula are typical of that seen in some molecular clouds. The gas density has a log-normal distribution with an average value of $10^3$ cm$^{-3}$. The size of the structures is 0.1-0.2 pc but this estimate is limited by the resolution of the observations. The mass ranges from 0.2 to 20 M$_{\odot}$ and the distribution of the more massive clumps follows a power law $dN/d\log(M) \sim M^{-1.4}$. We identify a mass-size relation with the same exponent as that found in GMCs ($M\sim L^{2.3}$) but only 15% of the mass of the cloud is in gravitationally bound structures. We conclude that the increase of pressure in the collision is strong enough to trigger the WNM-CNM transition caused by the interplay between turbulence and thermal instability as self-gravity is not dominating the dynamics.Comment: 16 pages, A&A, in pres

The new Mars climate database

Not available

Comparison of absolute gain photometric calibration between Planck/HFI and Herschel/SPIRE at 545 and 857 GHz

We compare the absolute gain photometric calibration of the Planck/HFI and Herschel/SPIRE instruments on diffuse emission. The absolute calibration of HFI and SPIRE each relies on planet flux measurements and comparison with theoretical far-infrared emission models of planetary atmospheres. We measure the photometric cross calibration between the instruments at two overlapping bands, 545 GHz / 500 $\mu$m and 857 GHz / 350 $\mu$m. The SPIRE maps used have been processed in the Herschel Interactive Processing Environment (Version 12) and the HFI data are from the 2015 Public Data Release 2. For our study we used 15 large fields observed with SPIRE, which cover a total of about 120 deg^2. We have selected these fields carefully to provide high signal-to-noise ratio, avoid residual systematics in the SPIRE maps, and span a wide range of surface brightness. The HFI maps are bandpass-corrected to match the emission observed by the SPIRE bandpasses. The SPIRE maps are convolved to match the HFI beam and put on a common pixel grid. We measure the cross-calibration relative gain between the instruments using two methods in each field, pixel-to-pixel correlation and angular power spectrum measurements. The SPIRE / HFI relative gains are 1.047 ($\pm$ 0.0069) and 1.003 ($\pm$ 0.0080) at 545 and 857 GHz, respectively, indicating very good agreement between the instruments. These relative gains deviate from unity by much less than the uncertainty of the absolute extended emission calibration, which is about 6.4% and 9.5% for HFI and SPIRE, respectively, but the deviations are comparable to the values 1.4% and 5.5% for HFI and SPIRE if the uncertainty from models of the common calibrator can be discounted. Of the 5.5% uncertainty for SPIRE, 4% arises from the uncertainty of the effective beam solid angle, which impacts the adopted SPIRE point source to extended source unit conversion factor (Abridged)Comment: 13 pages, 10 figures; Incorporates revisions in response to referee comments; cross calibration factors unchange

Evolution of dust in the Orion Bar with Herschel: I. Radiative transfer modelling

Interstellar dust is a key element in our understanding of the interstellar medium and star formation. The manner in which dust populations evolve with the excitation and the physical conditions is a first step in the comprehension of the evolution of inter- stellar dust. Within the framework of the Evolution of interstellar dust Herschel key program, we have acquired PACS and SPIRE spec- trophotometric observations of various photodissociation regions, to characterise this evolution. The aim of this paper is to trace the evolution of dust grains in the Orion Bar photodissociation region. We use Herschel/PACS (70 and 160 mic) and SPIRE (250, 350 and 500 mic) together with Spitzer/IRAC observations to map the spatial distribution of the dust populations across the Bar. Brightness profiles are modelled using the DustEM model coupled with a radiative transfer code. Thanks to Herschel, we are able to probe finely the dust emission of the densest parts of the Orion Bar with a resolution from 5.6" to 35.1". These new observations allow us to infer the temperature of the biggest grains at different positions in the Bar, which reveals a gradient from \sim 80 K to 40 K coupled with an increase of the spectral emissivity index from the ionization front to the densest regions. Combining Spitzer/IRAC observations, which are sensitive to the dust emission from the surface, with Herschel maps, we have been able to measure the Orion Bar emission from 3.6 to 500 mic. We find a stratification in the different dust components which can be re- produced quantitatively by a simple radiative transfer model without dust evolution. However including dust evolution is needed to explain the brightness in each band. PAH abundance variations, or a combination of PAH abundance variations with an emissivity enhancement of the biggest grains due to coagulation give good results.Comment: 11 pages, 12 figure

Physical structure of the photodissociation regions in NGC 7023: Observations of gas and dust emission with <i>Herschel</i>

The determination of the physical conditions in molecular clouds is a key step towards our understanding of their formation and evolution of associated star formation. We investigate the density, temperature, and column density of both dust and gas in the photodissociation regions (PDRs) located at the interface between the atomic and cold molecular gas of the NGC 7023 reflection nebula. We study how young stars affect the gas and dust in their environment. Our approach combining both dust and gas delivers strong constraints on the physical conditions of the PDRs. We find dense and warm molecular gas of high column density in the PDRs

Planck pre-launch status : The Planck mission

Peer reviewe

Planck intermediate results: XXVII High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE

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.\u20325 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. We perform a dedicated Herschel-SPIRE follow-up of 234 such Planck targets, finding a significant excess of red 350 and 500 \u3bcm 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 350 \u3bcm, with 3% peaking at 500 \u3bcm, and none peaking at 250 \u3bcm. 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 10\u3c3. The SPIRE photometric redshifts of galaxies in overdensities suggest a peak at z 43 2, assuming a single common dust temperature for the sources of Td = 35 K. Under this assumption, we derive an infrared (IR) luminosity for each SPIRE source of about 4 7 1012 L 99, yielding star formation rates of typically 700 M 99 yr-1. If the observed overdensities are actual gravitationally-bound structures, the total IR luminosity of all their SPIRE-detected sources peaks at 4 7 1013 L 99, leading to total star formation rates of perhaps 7 7 103 M 99yr-1 per overdensity. Taken together, these sources show the signatures of high-z (z > 2) protoclusters of intensively star-forming galaxies. All these observations confirm the uniqueness of our sample compared to reference samples and demonstrate the ability of the all-sky Planck-HFI cold sources to select populations of cosmological and astrophysical interest for structure formation studies