Within the Herschel key project “The Warm And Dense ISM” (WADI) we systematically observea number of prominent photon-dominated regions (PDRs) to measure the impact of varying UVfields on the energy balance, the chemical and dynamical structure of heated molecularclouds.

Ultra-compact dwarf galaxies (UCDs) are predominatly found in the cores of nearby galaxy clusters. Besides the Fornax and Virgo cluster, UCDs have also been confirmed in the twice as distant Hydra I and Centaurus clusters. Having (nearly) complete samples of UCDs in some of these clusters allows the study of the bulk properties with respect to the environment they are living in. Moreover, the relation of UCDs to other stellar systems in galaxy clusters, like globular clusters and dwarf ellipticals, can be investigated in detail with the present data sets. The general finding is that UCDs seem to be a heterogenous class of objects. Their spatial distribution within the clusters is in between those of globular clusters and dwarf ellipticals. In the colour-magnitude diagram, blue/metal-poor UCDs coincide with the sequence of nuclear star clusters, whereas red/metal-rich UCDs reach to higher masses and might have originated from the amalgamation of massive star cluster complexes in merger or starburst galaxies.

During these past decades, our knowledge of evolutionary and structural properties of stars of different mass and chemical composition is significantly improved. This result has been achieved as a consequence of our improved capability in understanding and describing the physical behaviour of matter in the different thermal regimes characteristic of the various stellar mass ranges and evolutionary stages. This notwithstanding, the current generation of stellar models is still affected by significant and, usually, not negligible uncertainties. These uncertainties are related to our poor knowledge of some physical proceses occurring in the real stars such as, for instance, some thermodynamical processes, nuclear reaction rates, as well as the efficiency of mixing processes. These drawbacks of stellar models have to be properly taken into account when comparing theory with observations in order to derive relevant information about the properties of both resolved and unresolved stellar populations. On the other hand, observations of both field and cluster stars can provide fundamental benchmarks for constraining the reliability and accuracy of the theoretical framework. In the following we review some important evolutionary and structural properties of very-low and low-mass stars, as well as the most important uncertainties affecting the stellar models for such stars. We show what are the main sources of uncertainty along the main evolutionary stages, and discuss the present level of agreement between theory and observations.


This and the following two chapters present a general introduction to the subject of observing magnetic fields in stars using spectropolarimetry. The three chapters will consider (1) the basic physics of the Zeeman and related effects, direct deductions about stellar magnetic fields that may be made where this effect is detected, and how such measurements have provided much information about the Sun and other magnetic stars; (2) how spectropolarimetric observations of magnetic stars may be modelled, and how such techniques may be used to extract much detailed information about the stellar magnetic field and other characteristics of the magnetized stellar atmosphere; and (3) how other magnetic effects such as the Hanle effect and continuum polarisation may be used to detect fields in a variety of stellar types such as white dwarfs, and how the current body of observational knowledge about magnetic stars may be integrated into a roughly coherent, provisional scenario of field origin and evolution.
In this chapter we survey the physics of an atom in a magnetic field (the Zeeman effect and its relatives), and identify ways in which magnetic effects on the atomic energy level structure may be used to detect and characterise stellar magnetic fields. We survey some of the basic features of magnetism in the Sun. We then describe how the available data may be used to deduce simple averages of various magnetic quantities over the stellar surface (for example, the “mean longitudinal field”) and how such simple field measurements are used to develop and explore the “oblique (dipole) rotator model” of magnetism for a group of middle main sequence stars called the “magnetic Ap stars”.

Directional detection of Dark Matter is a promising search strategy. However, to perform such kind of detection, the recoiling tracks have to be accurately reconstructed: direction, sense and position in the detector volume. In order to optimize the track reconstruction and to fully exploit the data from the MIMAC detector, we developed a likelihood method dedicated to the track reconstruction. This likelihood approach requires a full simulation of track measurements with MIMAC in order to compare real tracks to simulated ones. Finally, we found that the MIMAC detector should have the required performance to perform a competitive directional detection of Dark Matter.

Earthshine is sunlight that has been reflected from the dayside Earth onto the dark side of the Moon and back again to Earth. In recent times, there has been a renewed interest in ground-based visible and near infrared measurements of the earthshine, as a proxy for exoplanet observations. Observations of the earthshine allow us to explore and characterize the globally-integrated photometric, spectral and polarimetric features of the Earth, and to extract precise information on what are the distinctive characteristics of our planet, and life in particular. They also allow us to quantify how this features changes with time and orbital configurations.

We present the BinaMIcS project, its goals and the first BinaMIcS spectropolarimetric observations obtained with Narval at TBL and ESPaDOnS at CFHT: dedicated time-series for targeted hot and cool close double-line spectroscopic (SB2) binaries and a survey of hot close SB2 binaries. The very first results are also presented. In particular, our first survey observations seem to show a lack of magnetic fields in hot close binaries compared to single stars.

The Wide-field Infrared Survey Explorer (WISE) will map the whole sky in 6 months followingits launch and in-orbit checkout. Launch is currently scheduled for November, 2009. WISEshould cover more than 95% of sky with sensitvities of 120, 160, 650 & 2600 μJy inbands centered at 3.3, 4.7, 12 & 23 μm wavelength. The angular resolution shouldbe 6'' except at 23 μm where diffraction gives 12''.The low thermal background makes telescopes at Dome C very useful forfollow-up observations of WISE sources.

We study the potential impact of a photometric search for transiting exoplanets from Dome C. In the past year, four new transiting exoplanets have been found by ground-based surveys, including three detected by our follow-up of OGLE transit candidates with FLAMES/UVES on the VLT. Based on the experience of this survey, we have built a simulation to predict the expected number of transiting exoplanet detections from photometric searches. We apply these simulations to a possible survey based at Concordia. We find that the Antarctica location solves the two main limitations of ground-based transit surveys: the diurnal-cycle time sampling, and the hour-timescale systematic photometric variations. The expected numbers of detections are much larger than for other ground-based surveys. They show the high potential of such projects at Dome C, even with a small telescope.

We calibrate and then use the relation between equivalent width (EW) and full–width–half–maximum (FWHM) of metallic absorption lines in the spectra of RR Lyrae stars to estimate a new upper limit of Vrotsini ≤ 6 km.s−1 on their axial equatorial rotational velocities, and to derive the variations of macroturbulent velocities in their atmospheres during pulsation cycles. Finally, we present a simple way to estimate macroturbulent/rotational velocity from FWHM of the cross–correlation function.

The interpretation of water lines in red supergiant stellar atmospheres has been much debated over the past decade. The introduction of the so-called MOLspheres to account for near-infrared “extra” absorption has been controversial. We propose that non-LTE effects should be taken into account before considering any extra-photospheric contribution.

After a brief introduction on the radiative transfer treatment and the inadequacy of classical treatments in the case of large-scale systems such as molecules, we present a new code, based on preconditioned Krylov subspace methods. Preliminary results suggest that NLTE effects lead to deeper water bands, as well as extra cooling.

Dwarf elliptical galaxies are frequently excluded from bright galaxy samples because they do not follow the same linear relations in diagrams involving effective half light radii, Re, or mean effective surface brightnesses, ⟨μ⟩e. However, using two linear relations which unite dwarf and bright elliptical galaxies we explain how these lead to curved relations when one introduces either Re or ⟨μ⟩e. In particular, the curved ⟨μ⟩e − Re relation is derived here. This and other previously misunderstood curved relations, once heralded as evidence for a discontinuity between faint and bright elliptical galaxies at MB ≈ −18 mag, actually support the unification of such galaxies as a single population whose structure (i.e. stellar concentration) varies continuously with stellar luminosity and mass.

In the long story of interstellar PAHs, computations have played and are still playing afundamental role in connection with experiments and observations. From the very firstcalculations of the IR spectra of small PAHs in the late eighties to the more recent ones,every aspect of the research linked to the PAH hypothesis has evolved dramatically: thesize and the variety of the molecules considered, the techniques used, the precision ofthe astronomical observations ... The initial landscape has completelychanged though the quest is still the same, that is to correlate the so-called UIR bandsspectra ubiquitous in the ISM (Inter Stellar Medium) with a chemical family of molecules,the PAHs. An historical review of the 25 years of this quest is presented here, focusingon the computational part.

The DMTPC directional dark matter detection experiment is a low-pressure CF4 gas time projection chamber, instrumented with charge and scintillation photon readout. This detector design strategy emphasizes reconstruction of WIMP-induced nuclear recoil tracks, in order to determine the direction of incident dark matter particles. Directional detection has the potential to make the definitive observation of dark matter using the unique angular signature of the dark matter wind, which is distinct from all known backgrounds. This talk will briefly review the experimental technique and current status of DMTPC.

Low-mass stars (<2–2.5 M๏) exhibit, at all the stages of theirevolution, signatures of processes that require challenging modelingbeyond the standard stellar theory.In this paper we focus on their peculiarities while they climb thered giant branch (RGB).We first review canonical evolution along the RGB and compare theclassicle predictions of the so-called first dredge-upwith observational data in various environments.We show how clear spectroscopic diagnostics probe the nucleosynthesisand the internal mixing mechanisms that drive RGB stars.Coherent data reveal in particular the existence of a nonstandardand shallow mixing process that changes the surface abundances at the so-called RGB bump.We discuss the current understanding of the connection betweenthis extra-mixing and stellar rotation and conclude on the remaining open questions.

This article first provides a historical and detailed introduction to the image formation models for diluted pupils array and their densified versions called hypertelescopes. We propose in particular an original derivation showing that densification using a periscopic setting like in Michelson’s 20 −  foot interferometer, or using inverted Galilean telescopes are fully equivalent. After a review based on previous reference studies (Tallon & Tallon-Bosc 1992; Labeyrie 1996; Aime 2008 and Aime et al. 2012), the introductory part ends with a tutorial section for simulating optical interferometric images produced by cophased arrays. We illustrate in details how the optical image formation model can be used to simulate hypertelescopes images, including sampling issues and their effects on the observed images.

In a second part of the article, we address the issue of restoring hypertelescope images and present numerical illustrations obtained for classical (constrained Maximum Likelihood) methods. We also provide a detailed survey of more recent deconvolution methods based on sparse representations and of their spread in interferometric image reconstruction.

The last part of the article is dedicated to two original and numerical studies. The first study shows by Monte Carlo simulations that the restoration quality achieved by constrained ML methods applied to photon limited images obtained from a diluted array on a square grid, or from a densified array (without spectral aliasing) on a grid, are essentially equivalent. The second study shows that it is possible to recover in hypertelescopes images quasi point sources that are not only far outside the clean field, but also superimposed on the replicas of other objects. This is true at least for the considered pupil array and in the limit of vanishing noise.

Although it presently includes convective overshoot, microscopic diffusion, gravitational settling and radiative acceleration, the standard model of stellar structure is still unable to account for various observational facts, and there is now a large consensus that some extra mixing must occur in the radiation zones. To account for such mixing, the minimalist approach consists in introducing a parametrized turbulent diffusivity, and to adjust it so as to match the observations. A better way is to strive to implement the physical processes that may be responsible for this mixing, in particular shear-induced turbulence and large-scale meridional circulation, which both are linked with the differential rotation of the star. To describe that rotational mixing, as we call it, one has thus to follow the evolution of the internal rotation profile. By making some plausible assumptions, its is possible to reduce the advection of angular momentum through the 2-D circulation to a 1-D process, and that of the chemical elements to a vertical diffusion. It is then possible to implement these transports in a 1-D stellar evolution code.
In massive stars, angular momentum is transported mainly by the meridional circulation, and there is good agreement between the observations and the predictions based on the rotational mixing. This not so for solar-type stars where another, more efficient mechanism is required to transport angular momentum. A fossil magnetic field has been invoked, but recently it has been shown that such a field would connect with the convection zone, and imprint its differential rotation on the radiation zone, which is not observed. The other candidate is the transport of angular momentum by the internal gravity waves that are emitted at the base of the convection zone; although their treatment is still somewhat crude, it appears that they can explain both the quasi-uniform rotation of the solar interior, and the depletion of lithium observed in such stars.

Atomic hydrogen escaping from the extrasolar giant planet HD 209458b provides the largest observational signature ever detected for an extrasolar planet atmosphere. In fact, the upper atmosphere of this planet is evaporating. Observational evidences and interpretations coming from various models are reviewed. Implications for exoplanetology are discussed.

This paper concentrates on the control aspects of Adaptive Optics (AO) systems and includes a prior exposure to linear control systems from the “classical” point of view. The AO control problem is presented and the well-established optimized modal gain integral control approach is discussed. The design of a controller from a modern control point of view is addressed by means of a linear quadratic Gaussian control methodology. The proposed approach emphasizes the ability of the adaptive optics loop to reject the atmospheric aberration. We derive a diagonal state space system which clearly separates the dynamics of the plant (deformable mirror & wavefront sensor) from the disturbance dynamics (atmospheric model). This representation facilitates the numerical resolution of the problem. A frequency analysis is carried out to check performance and robustness specifications of the multiple-input multiple-output feedback system. The effectiveness of the approach is demonstrated through numerical experiments.

The magnetorotational instability (MRI) is the most likely source of MHD turbulence in accretion disks. Recently, it has been realized that microscopic diffusion coefficients (viscosity and resistivity) are important in determining the saturated state of the turbulence and thereby the rate of angular momentum transport. In this paper, we use a set of numerical simulations performed with a variety of numerical methods to investigate the dependance of α, the rate of angular momentum transport, on these coefficients. We show that α is an increasing function of the magnetic Prandtl number Pm, the ratio of viscosity over resistivity. In the absence of a mean field, we also find that MRI–induced MHD turbulence decays at low Pm.