Institut National Des Sciences De Research Articles

New macaque fossil remains from Morocco

This work has been funded by Palarq Foundation, Spanish Ministry of Culture and Sport (42-T002018042853 and 170-T002019038589), Direction of Cultural Heritage (Ministry of Culture and Communication, Morocco), Faculty of Sciences (Mohamed 1r University of Oujda, Morocco), INSAP (Institut National des Sciences de l’Archeologie et du Patrimoine), Agencia Estatal de Investigacion (Spanish Ministry of Science, Innovation and Universities: CGL2016-76431-P, CGL2016-80975-P, CGL2016-80000-P, CGL2017-82654-P, PGC2018-095489-B-I00, and PGC2018-093925-B-C31, AEI/FEDER-UE), and Research Group Support of the Generalitat de Catalunya (2017 SGR 116, 2017 SGR836, and 2017 SGR 859). The research by D.M.A., R.S-R, M.G.C., P.S., C.L., and E.D. is funded by CERCA Programme/Generalitat de Catalunya. A.M.A and M.F. are beneficiaries of a fellowship from the Erasmus Mundus Program to do the Master in Quaternary and Prehistory at the Universitat Rovia i Virgili (Tarragona, Spain). A.R.-H. is the beneficiary of a postdoctoral scholarship from the MICINN, Subprograma Juan de la Cierva (IJC-037447-I), and member of theconsolidated research group 2017 SGR 1040 of the Generalitat de Catalunya. The Institut Catala de Paleoecologia Humana i Evolucio Social (IPHES-CERCA) has received financial support from the Spanish Ministry of Science and Innovation through the ‘Maria de Maeztu’ program for Units of Excellence (CEX2019-000945-M).

Long-term History in a Moroccan Oasis Zone: The Middle Draa Project 2015

AbstractThis article describes the research questions and presents the initialamsdates of the Middle Draa Project (southern Morocco), a collaborative field survey project between the University of Leicester and the Institut National des Sciences de l’Archéologie et du Patrimoine (insap) of Morocco. Starting from a very low baseline of past archaeological research in this pre-desert valley, the overall objective of the project is to establish the extent, character and chronology of the rich archaeology of the Wadi Draa. The results presented here detail a hitherto unknown phase of major occupation in the Draa in the 4th-6th centuriesadevidenced by complex hilltop settlements and extensive cairn cemeteries (an initial typology is presented). A second medieval phase comprised major urban centres that are contemporary with the Almoravid and Almohad periods of Moroccan history. Alongside these urban centres, there are the remains of substantial mudbrick oasis settlements and irrigation and field-systems of a contemporary date. A key contribution of this paper concerns the construction of an outline chronology based upon initial analysis of the ceramics collected, but crucially supplemented and supported by a major program ofamsdating. The remote sensing and field survey data collected by the project enable us to develop some hypotheses concerning the long-term history of this important oasis valley.

Fourth CLIVAR Workshop on the Evaluation of ENSO Processes in Climate Models: ENSO in a Changing Climate

The organizers acknowledge the generous support of the World Climate Research Programme/CLIVAR, the Centre National de la Recherche Scientifique–Institut National des Sciences de l’Univers (CNRS-INSU), the LabEx L-IPSL, and Sorbonne Universites and wish to thank Lei Han, from the International CLIVAR Global Project Office in Qingdao, China, for his invaluable help in organizing this workshop.

Measuring subhalo mass in redMaPPer clusters with CFHT Stripe 82 Survey

We use the shear catalog from the CFHT Stripe-82 Survey to measure the subhalo masses of satellite galaxies in redMaPPer clusters. Assuming a Chabrier Initial Mass Function (IMF) and a truncated NFW model for the subhalo mass distribution, we find that the sub-halo mass to galaxy stellar mass ratio increases as a function of projected halo-centric radius $r_p$, from $M_{\rm sub}/M_{\rm star}=4.43^{+ 6.63}_{- 2.23}$ at $r_p \in [0.1,0.3]$ $h^{-1}Mpc$ to $M_{\rm sub}/M_{\rm star}=75.40^{+ 19.73}_{- 19.09}$ at $r_p \in [0.6,0.9]$ $h^{-1}Mpc$. We also investigate the dependence of subhalo masses on stellar mass by splitting satellite galaxies into two stellar mass bins: $10<\log(M_{\rm star}/M_{\rm sun})<10.5$ and $11<\log(M_{\rm star}/M_{\rm sun})<12$. The best-fit subhalo mass of the more massive satellite galaxy bin is larger than that of the less massive satellites: $\log(M_{\rm sub}/M_{\rm sun})=11.14 ^{+ 0.66 }_{- 0.73}$ ($M_{\rm sub}/M_{\rm star}=19.5^{+19.8}_{-17.9}$) versus $\log(M_{\rm sub}/M_{\rm sun})=12.38 ^{+ 0.16 }_{- 0.16}$ ($M_{\rm sub}/M_{\rm star}=21.1^{+7.4}_{-7.7}$).

A panorama of Astronomy in the coming decade

This presentation was done as an introductive lesson at the summer school BasMatI (Bases Mathematiques pour l'instrumentation et le traitement du signal en Astronomie) held in Porquerolles in June 2015. The goal is to present the main scientific questions in Astrophysics as well as the main instrumental developments the astronomical community is considering for the next decade. In a first part of this paper, I will present the recent prospective exercise concluded in October 2014 by the Institut National des Sciences de l'Univers (INSU of CNRS) as well as the European ASTRONET Science Vision and Infrastructure Roadmap, updated in 2014. I will then present the main instruments the French astronomical community is using and developing.

A new device to follow temporal variations of oxygen demand in deltaic sediments: the LSCE benthic station

A new benthic station equipped with oxygen microelectrodes and environmental sensors was developed by Laboratoire des Sciences du Climat et de L'Environnement (LSCE) and Division Technique of the Institut National des Sciences de L'Univers (DT‐ INSU) to perform in situ time series monitoring of sediment oxygen demand, linked to the mineralization of organic matter. The time series typically cover periods of 2‐ 3 months, with a base frequency of 1 set of oxygen profiles per day. The profiling head assessed the lateral heterogeneity of the sediment oxygen demand at the beginning of the time series over a 0.8‐ m long rectangle to discriminate spatial and temporal variability. A continuous recalibration is performed using a moored oxygen optode anchored to the benthic station together with a set of environmental sensors. These sensors (turbidity, temperature, salinity, and oxygen) can trigger a high‐ frequency profiling mode to investigate the fate of particulate organic matter delivered during floods, resuspension, and deposition events. Deployments of the benthic station were performed in the Rhone River subaqueous delta (Mediterranean Sea). We show that “stable” periods (when neither floods nor storms occur) were characterized by a stable oxygen demand. In the case of resuspension events, an increase of the sediment oxygen demand by a factor of 2‐ 3 with a relaxation time of 1 day was observed, indicating that the new benthic station can adequately capture the impact of resuspension events on the oxygen demand in deltaic sediments.

The Open Cluster NGC 2437 (Messier 46)11Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and Commissariat à l'énergie atomique et aux énergies alternative (CEA)/Dapnia, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of

ABSTRACTThe stellar content of the open cluster NGC 2437 (Messier 46) is investigated using moderately deep u∗, g′, and r′ MegaCam images. When compared with solar metallicity isochrones, the (g′,u′ - g′) and (r′,g′ - r′) CMDs are consistent with an age log(tyr) = 8.35 ± 0.15, a distance modulus μ0 = 11.05 ± 0.05, and a color excess E(B - V) = 0.115 ± 0.035. The r′ luminosity function (LF) of main sequence stars in the magnitude range r′ < 17 (i.e., masses ≳0.8 M⊙) has a shape that follows solar neighborhood star counts. However, at fainter magnitudes, the cluster LF is flat, in contrast with what would be expected from solar neighborhood counts. The clustering properties of stars in NGC 2437 are investigated by examining the two-point angular correlation functions of main sequence stars in different brightness ranges. Main sequence stars fainter than r′ = 17 are less centrally concentrated than brighter stars and are found over a larger area of the sky, suggesting that there is a corona of faint main sequence stars around NGC 2437. Based on the flat LF and extended spatial distribution of faint stars, it is concluded that NGC 2437 is actively shedding stars with masses ≲0.8 M⊙.

Mauna Kea Sky Transparency from CFHT SkyProbe Data11Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

ABSTRACTNighttime sky-transparency statistics on Mauna Kea are reported based on data from the Canada-France-Hawaii Telescope SkyProbe monitor. We focus on the period beginning with the start of MegaCam wide-field optical imager operations in 2003 and continuing for almost three years. Skies were clear enough to observe on 76% of those nights; attenuations were less than 0.2 mag up to 60% of the time. An empirical model of cloud attenuation and duration is presented allowing us to further characterize the photometric conditions. This is a good fit to the SkyProbe data and indicates that Mauna Kea skies are truly photometric (without clouds) an average of 56% of the time, with moderate seasonal variation. Continuous monitoring of transparency during the night is necessary to overcome fluctuations in attenuation due to thin clouds.

Large-scale magnetic topologies of early M dwarfs★

We present here additional results of a spectropolarimetric survey of a small sample of stars ranging from spectral type M0 to M8 aimed at investigating observationally how dynamo processes operate in stars on both sides of the full convection threshold (spectral type M4). The present paper focuses on early M stars (M0-M3), that is above the full convection threshold. Applying tomographic imaging techniques to time series of rotationally modulated circularly polarized profiles collected with the NARVAL spectropolarimeter, we determine the rotation period and reconstruct the large-scale magnetic topologies of six early M dwarfs. We find that early-M stars preferentially host large-scale fields with dominantly toroidal and non-axisymmetric poloidal configurations, along with significant differential rotation (and long-term variability); only the lowest-mass star of our subsample is found to host an almost fully poloidal, mainly axisymmetric large-scale field resembling those found in mid-M dwarfs. This abrupt change in the large-scale magnetic topologies of M dwarfs (occurring at spectral type M3) has no related signature on X-ray luminosities (measuring the total amount of magnetic flux); it thus suggests that underlying dynamo processes become more efficient at producing large-scale fields (despite producing the same flux) at spectral types later than M3. We suspect that this change relates to the rapid decrease in the radiative cores of low-mass stars and to the simultaneous sharp increase of the convective turnover times (with decreasing stellar mass) that models predict to occur at M3; it may also be (at least partly) responsible for the reduced magnetic braking reported for fully convective stars. Based on observations obtained at the Telescope Bernard Lyot (TBL), operated by the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique of France. E-mail: donati@ast.obs-mip.fr (J-FD); jmorin@ast.obs-mip.fr (JM); petit@ast.obs-mip.fr (PP); xavier.delfosse@obs.ujf-grenoble.fr (XD); thierry.forveille@obs.ujf-grenoble.fr (TF); auriere@ast.obs-mip.fr (MA); remi.cabanac@ast.obs-mip.fr (RC); dintrans@ast.obs-mip.fr (BD); rfares@ast.obs-mip.fr (RF); tgastine@ast.obs-mip.fr (TG); mmj@st-and.ac.uk (MMJ); lignieres@ast.obs-mip.fr (FL); fpaletou@ast.obs-mip.fr (FP); julio.ramirez@obspm.fr (JCRV); sylvie.theado@ast.obs-mip.fr (ST)

The Identification of New Stellar Groupings in the M81 Debris Field1,1Based on observations obtained with the MegaPrime/MegaCam, a joint project of the CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and

ABSTRACTThe stellar content of the debris field around M81 is investigated using deep images obtained with MegaCam on the Canada-France-Hawaii Telescope. Three new concentrations of bright main-sequence stars and red supergiants are identified within ∼20 kpc of M81. These systems have integrated brightnesses MV ∼ -11 and surface brightnesses μV ∼ 27–28 mag arcsec-2. The main-sequence turnoffs are consistent with an age of ∼30 Myr, while the presence of a well-developed red supergiant plume indicates that their stellar content is not coeval, as they also formed stars ∼100 Myr in the past. The photometric properties of the red supergiants indicate that the young stars in these systems have metallicities that are comparable to those of other objects in the debris field. The H I density near these groupings comfortably exceeds the threshold required to trigger star formation. Based on the close proximity of these objects to M81, coupled with their extended sizes and low inferred masses, it is argued that they will not be long-lived structures, but will probably dissipate within the next ∼1 Gyr.

The VVDS-SWIRE-GALEX-CFHTLS surveys: physical properties of galaxies at z below 1.2 from photometric data

Measuring the build-up of stellar mass is one of the main objectives of studies of galaxy evolution. Traditionally, the mass in stars and the star formation rates have been measured by different indicators, such as photometric colours, emission lines, and the UV and IR emission. We intend to show that it is possible to derive the physical parameters of galaxies from their broad-band spectral energy distribution out to a redshift of 1.2. This method has the potential to yield the physical parameters of all galaxies in a single field in a homogeneous way, thus overcoming problems with the sample size that particularly plague methods relying on spectroscopy. We use an extensive dataset, assembled in the context of the VVDS survey, which reaches from the UV to the IR and covers a sample of 84 073 galaxies over an area of 0.89 deg^2. We also use a library of 100 000 model galaxies with a wide variety of star formation histories (in particular including late bursts of star formation). We find that we can determine the physical parameters stellar mass, age, and star formation rate with good confidence. We validate the star formation rate determination in particular by comparing it to a sample of spectroscopically observed galaxies with an emission-line measurement. While the attenuation in the galaxies shows more scatter, the mean over the sample is unbiased. Metallicity, however, cannot be measured from rest-frame optical photometry alone. As a first application we use our sample to build the number density function of galaxies as a function of stellar mass, specific star formation rate, and redshift. We are then able to study whether the stellar mass function at a later time can be predicted from the stellar mass function and star formation rate distribution at an earlier time. We find that, between redshifts of 1.02 and 0.47, the predicted growth in stellar mass from star formation agrees with the observed one. However, the predicted stellar mass density for massive galaxies is lower than observed, while the mass density of intermediate mass galaxies is overpredicted. This apparent discrepancy can be explained by major and minor mergers. Indeed, when comparing with a direct measurement of the major merger rate from the VVDS survey, we find that major mergers can account for about half of the mass build-up at the massive end. Minor mergers are very likely to contribute the missing fraction. Based on data obtained with the European southern observatory Very Large Telescope, Paranal, Chile, programme 070A-9007(A) and on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.

Photometric redshifts as a tool for studying the Coma cluster galaxy populations

Aims. We apply photometric redshift techniques to an investigation of the Coma cluster galaxy luminosity function (GLF) at faint magnitudes, in particular in the u* band where basically no studies are presently available at these magnitudes. Methods: Cluster members were selected based on probability distribution function from photometric redshift calculations applied to deep u^*, B, V, R, I images covering a region of almost 1 deg2 (completeness limit R ~ 24). In the area covered only by the u* image, the GLF was also derived after a statistical background subtraction. Results: Global and local GLFs in the B, V, R, and I bands obtained with photometric redshift selection are consistent with our previous results based on a statistical background subtraction. The GLF in the u* band shows an increase in the faint end slope towards the outer regions of the cluster. The analysis of the multicolor type spatial distribution reveals that late type galaxies are distributed in clumps in the cluster outskirts, where X-ray substructures are also detected and where the GLF in the u* band is steeper. Conclusions: We can reproduce the GLFs computed with classical statistical subtraction methods by applying a photometric redshift technique. The u* GLF slope is steeper in the cluster outskirts, varying from α ~ -1 in the cluster center to α ~ -2 in the cluster periphery. The concentrations of faint late type galaxies in the cluster outskirts could explain these very steep slopes, assuming a short burst of star formation in these galaxies when entering the cluster. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is also partly based on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. Also based on data from W. M. Keck Observatory which is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA. It was made possible by the generous financial support of the W. M. Keck Foundation.

Testing the forward modeling approach in asteroseismology

Context: Balloon 090100001, the brightest of the known pulsating hot B subdwarfs, exhibits simultaneoulsy both short- and long-period pulsation modes, and shows relatively large amplitudes for its dominant modes. For these reasons, it has been studied extensively over the past few years, including a successful experiment carried out at the Canada-France-Hawaii Telescope to pin down or constrain the value of the degree index l of several pulsation modes through multicolor photometry. Aims: The primary goal of this paper is to take advantage of such partial mode identification to test the robustness of our standard approach to the asteroseismology of pulsating subdwarf B stars. The latter is based on the forward approach whereby a model that best matches the observed periods is searched for in parameter space with no a priori assumption about mode identification. When successful, this method leads to the determination of the global structural parameters of the pulsator. As a bonus, it also leads, after the fact, to complete mode identification. For the first time, with the availability of partial mode identification for Balloon 090100001, we are able to evaluate the sensitivity of the inferred seismic model to possible uncertainty in mode identification. Methods: We carry out a number of exercises based on the double optimization technique that we developed within the framework of the forward modeling approach in asteroseismology. We use the set of ten periods corresponding to the independent pulsation modes for which values of l have been either formally identified or constrained through multicolor photometry in Balloon 090100001. These exercises differ in that they assume different a priori mode identification. Results: Our primary result is that the asteroseismic solution stands very robust, whether or not external constraints on the values of the degree l are used. Although this may come as a small surprise, the test proves to be conclusive, and small differences in mode identification among the ten modes do not affect in any significant way, at the typical accuracy presently achieved, the final emergent seismic model. This is due to the structure of the p-mode pulsation spectra in sdB stars. In all cases, the inferred structural parameters of Balloon 090100001 remain practically unchanged. They correspond, and this constitutes our second important result, to a star beyond the TAEHB with T_eff = 28 000 ± 1 200 K, log g = 5.383 ± 0.004, M⋆/Mȯ = 0.432 ± 0.015, and log{M_env/M⋆} = -4.89 ± 0.14. Other structural parameters are also derived. Based on photometric observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Some of the spectroscopic observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution.

The VIMOS VLT deep survey

We present a new K_s-band survey that represents a significant extension to the previous wide-field K_s-band imaging survey within the 0226-04 field of the VIMOS-VLT deep survey (VVDS). The new data add ~458 arcmin2 to the previous imaging program, thus allowing us to cover a total contiguous area of ~600 arcmin2 within this field. Sources were identified both directly on the final K-band mosaic image and on the corresponding, deep χ^2-g'r'i' image from the CFHT Legacy Survey in order to reduce contamination, while ensuring compilation of a truly K-selected catalogue down to the completeness limit of the K_s-band. The newly determined K_s-band magnitudes are used in combination with the ancillary multiwavelength data for determining accurate photometric redshifts. The final catalogue totals ~52 000 sources, out of which ~4400 have a spectroscopic redshift from the VVDS first epoch survey. The catalogue is 90% complete down to KVega = 20.5 mag. We present K_s-band galaxy counts and angular correlation function measurements down to this magnitude limit. Our results are in good agreement with previously published work. We show that using K magnitudes to determine photometric redshifts significantly lowers the incidence of catastrophic errors. The data presented in this paper are publicly available through the CENCOS database. Based on observations collected at the European Southern Observatory New Technology Telescope, La Silla, Chile, programme 075.A-0752(A), on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, programme 070.A-9007(A), and on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.

A robust morphological classification of high-redshift galaxies using support vector machines on seeing limited images

Context: Morphology is the most accessible tracer of the physical structure of galaxies, but its interpretation in the framework of galaxy evolution still remains a problem. Its dependence on wavelength renders the comparison between local and high redshift populations difficult. Furthermore, the quality of the measured morphology being strongly dependent on the image resolution, the comparison between different surveys is also a problem. Aims: We present a new non-parametric method to quantify morphologies of galaxies based on a particular family of learning machines called support vector machines. The method, which can be seen as a generalization of the classical C/A classification but with an unlimited number of dimensions and non-linear boundaries between decision regions, is fully automated and thus particularly well adapted to large cosmological surveys. The source code is available for download at http://www.lesia.obspm.fr/~huertas/galsvm.html Methods: To test the method, we use a seeing limited near-infrared (Ks band, 2,16 ?m) sample observed with WIRCam at CFHT at a median redshift of z ~ 0.8. The machine is trained with a simulated sample built from a local visually classified sample from the SDSS, chosen in the high-redshift sample's rest-frame (i band, 0.77 ?m) and artificially redshifted to match the observing conditions. We use a 12-dimensional volume, including 5 morphological parameters, and other characteristics of galaxies such as luminosity and redshift. A fraction of the simulated sample is used to test the machine and assess its accuracy. Results: We show that a qualitative separation in two main morphological types (late type and early type) can be obtained with an error lower than 20% up to the completeness limit of the sample (KAB ~ 22), which is more than 2 times better that what would be obtained with a classical C/A classification on the same sample and indeed comparable to space data. The method is optimized to solve a specific problem, offering an objective and automated estimate of errors that enables a straightforward comparison with other surveys. Selecting the training sample in the high-redshift sample rest-frame makes the results free from wavelength dependent effects and hence its interpretation in terms of evolution easier. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

The surprising magnetic topology of Sco: fossil remnant or dynamo output?

We report the discovery of a medium-strength (~0.5 kG) magnetic field on the young, massive star ? Sco (B0.2V), which becomes the third-hottest magnetic star known. Circularly polarized Zeeman signatures are clearly detected in observations collected mostly with the ESPaDOnS spectropolarimeter, recently installed on the 3.6-m Canada-France-Hawaii Telescope; temporal variability is also clearly established in the polarimetry, and can be unambiguously attributed to rotational modulation with a period close to 41 d. Archival ultraviolet (UV) spectra confirm that this modulation repeats over time-scales of decades, and refine the rotation period to 41.033 +/- 0.002 d. Despite the slow rotation rate of ? Sco, we none the less succeed in reconstructing the large-scale structure of its magnetic topology. We find that the magnetic structure is unusually complex for a hot star, with significant power in spherical-harmonic modes of degree up to 5. The surface topology is dominated by a potential field, although a moderate toroidal component is probably present. We fail to detect intrinsic temporal variability of the magnetic structure over the 1.5-yr period of our spectropolarimetric observations (in agreement with the stable temporal variations of the UV spectra), and infer that any differential surface rotation must be very small. The topology of the extended magnetic field that we derive from the photospheric magnetic maps is also more complex than a global dipole, and features in particular a significantly warped torus of closed magnetic loops encircling the star (tilted at about 90° to the rotation axis), with additional, smaller, networks of closed-field lines. This topology appears to be consistent with the exceptional X-ray properties of ? Sco and also provides a natural explanation of the variability observed in wind-formed UV lines. Although we cannot completely rule out the possibility that the field is produced through dynamo processes of an exotic kind, we conclude that its magnetic field is most probably a fossil remnant from the star formation stage. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. E-mail: donati@ast.obs-mip.fr (J-FD); idh@star.ucl.ac.uk (IDH); mmj@st-andrews.ac.uk (MMJ); petit@ast.obs-mip.fr (PP); claude.catala@obspm.fr (CC); jlandstr@uwo.ca (JDL); jean-claude.bouret@oamp.fr (J-CB); evelyne.alecian@obspm.fr (EA); jrb3@st-andrews.ac.uk (JRB); forveill@cfht.hawaii.edu (TF); fpaletou@ast.obs-mip.fr (FP); manset@cfht.hawaii.edu (NM)

TRIDENT: An Infrared Differential Imaging Camera Optimized for the Detection of Methanated Substellar Companions11Based on observations obtained at the Canada‐France‐Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

ABSTRACTWe describe a near‐infrared camera in use at the Canada‐France‐Hawaii Telescope (CFHT) and at the 1.6 m telescope of the Observatoire du mont Mégantic (OMM). The camera is based on a Hawaii‐1 1024 × 1024 HgCdTe array detector. Its main feature is the acquisition of three simultaneous images at three wavelengths across the methane absorption bandhead at 1.6 μm, enabling, in theory, an accurate subtraction of the stellar point‐spread function (PSF) and the detection of faint close, methanated companions. The instrument has no coronagraph and features fast data acquisition, yielding high observing efficiency on bright stars. The performance of the instrument is described, and it is illustrated by laboratory tests and CFHT observations of the nearby stars GL 526, υ And, and χ And. TRIDENT can detect (6 σ) a methanated companion with ΔH = 9.5 at 0.″5 separation from the star in 1 hr of observing time. Non–common‐path aberrations and amplitude modulation differences between the three optical paths are likely to be the limiting factors preventing further PSF attenuation. Instrument rotation and reference‐star subtraction improve the detection limit by a factor of 2 and 4, respectively. A PSF noise attenuation model is presented to estimate the non–common‐path wave‐front difference effect on PSF subtraction performance.

Spatial and temporal scales of variation in bacterioplankton community structure in the NW Mediterranean Sea

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 40:229-240 (2005) - doi:10.3354/ame040229 Spatial and temporal scales of variation in bacterioplankton community structure in the NW Mediterranean Sea Jean-François Ghiglione*, Marièle Larcher, Philippe Lebaron Observatoire Océanographique de Banyuls, Laboratoire Arago, Université Pierre et Marie Curie (Paris 6), Institut National des Sciences de l’Univers (INSU) CNRS-UMR-7621, BP 44, 66651 Banyuls-sur-mer Cedex, France *Email: ghiglione@obs-banyuls.fr ABSTRACT: An important query in marine microbial ecology is at what temporal and spatial scales variations in the structure of natural bacterial communities occur. Samples of different volumes were collected at different spatial (vertical and horizontal) and temporal (from hours to seasons) scales along a transect between a coastal station (26 m depth) and an offshore Microbial Observatory (1000 m depth) in the NW Mediterranean Sea. The structure of the bacterial communities was determined by capillary electrophoresis–single strand conformation polymorphism (CE–SSCP) fingerprinting of polymerase chain reaction (PCR)-amplified 16S rDNA. This technique is a powerful tool to compare natural microbial assemblages at different spatial or temporal scales. Similar bacterial assemblages were found up to 3.7 km from the coastal station, whereas significant changes were found over greater distances (from 9.3 to 33.3 km). Although the bacterial community structure did not change with depth at coastal and shallow stations, vertical changes were found at deeper stations, most likely due to vertical variations in physico-chemical and biogeochemical parameters. Temporal changes were mainly related to environmental variations that occurred at a seasonal scale and during phytoplankton blooms. Finally, we suggest that long-term studies, at least in the NW Mediterranean Sea, should involve a minimum sampling time scale of 2 wk and a shorter time-scale when environmental changes are detected by the real-time monitoring of a few basic parameters (i.e. fluorescence, temperature, salinity). Sampling strategies should also include different depths depending on the vertical structure of the water column, based on the same basic parameters. KEY WORDS: Bacteria · CE–SSCP · Community structure · Sampling strategy · Microbial observatory Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 40, No. 3. Online publication date: October 18, 2005 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2005 Inter-Research.

ESCOMPTE experiment: intercomparison of four aircraft dynamical, thermodynamical, radiation and chemical measurements

Among seven airplanes involved in the Experience sur Site pour COntraindre les Modèles de Pollution atmosphérique et de Transport d'Emission (ESCOMPTE) experiment in 2001, four measured classical meteorological parameters, radiation fluxes, trace gases and turbulence (for three among four): the Dornier 128 from the Institut für Meteorologie und Klimaforschung, the Fokker 27 ARAT from the Institut National des Sciences de l'Univers, the Merlin 4 and Piper Aztec 23 from Météo France. This paper presents the results of intercomparison flights between three pairs of aircraft. The results are very similar for mean parameters except for the horizontal wind measurements provided by the Merlin that showed a problem that is probably linked to the measurement of the aircraft velocity. Further investigation is required to know whether corrections are possible or not for these wind measurements. Turbulence is studied along two legs over a flat and homogeneous area: in spite of the heterogeneity of the measured functions (one leg is close to the top of the boundary layer), the comparison is rather good. The relative accuracy of the data provided to the data base is given. It easily allows to use the huge amount of aircraft data collected during the experiment with very few restrictions. We underline some points where efforts should be borne for future experiments: wind coupling between Inertial Navigation System data and Global Positioning System (GPS) data, CO and NO x measurements.

Application of a Bayesian Wind Profile Retrieval Technique to Radar Data Collected in the Alpine Southern Upslope Region and Comparison with Upstream Wind Profiler Measurements

In this paper, a new operational technique to retrieve the horizontal wind profile from Doppler radar measurements is used to carry out a statistical comparison of upslope and upstream wind profiles in the southern flank of the European Alps. The method relies upon a first-order velocity azimuth display (VAD) expansion of the radial velocity and allows for recovering, through Bayesian updates, the likeliest wind speed and direction at each height. The major advantage of this new approach over existing ones is that it does not require any preliminary dealiasing of the radar data. This original feature makes it very well suited to real-time operational purposes. The method has been applied to 1248 volumetric sequences collected during the recent Mesoscale Alpine Programme (MAP) experiment by the Swiss C-band Monte Lema radar located in the alpine upslope region. The resulting profiles are compared to simultaneous measurements obtained upstream by the French Institut National des Sciences de l'Univers (INSU)/Météo-France VHF wind profiler. This extensive comparison allows validating of the proposed Bayesian VAD and inferring of some statistical properties of the wind profile during precipitation events in the southern Alps.