GEPI

Saint-Martin-Boulogne, France
Saint-Martin-Boulogne, France
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Desmurs J.-F.,Observatorio Astronomico Nacional | Baudry A.,Laboratory Observatoire Aquitain Des Science Of Lunivers | Sivagnanam P.,GEPI | Henkel C.,MPIfR | And 2 more authors.
Astronomy and Astrophysics | Year: 2010

Aims. The aim of this study is to investigate the physical properties of molecular envelopes of planetary nebulae (PNe) in their earliest stages of evolution. Methods. Using the 100 m telescope at Effelsberg, we have undertaken a high sensitivity discrete source survey for the first excited state of OH maser emission (J = 5/2, 2Π3/2 at 6 GHz) in the direction of PNe and proto-planetary nebulae (PNe) exhibiting 18 cm OH emission (main and/or satellite lines), and we further validate our detections using the Nançay radio telescope at 1.6-1.7 GHz and MERLIN interferometer at 1.6-1.7 and 6 GHz. Results. Two sources have been detected at 6035 MHz (5 cm), both of them are young (or very young) PNe. The first one is a confirmation of the detection of a weak 6035 MHz line in Vy 2-2. The second one is a new detection, in K 3-35, which was already known to be an exceptional late type star because it exhibits 1720 MHz OH emission. The detection of 6035 MHz OH maser emission is confirmed by subsequent observations made with the MERLIN interferometer. These lines are very rarely found in evolved stars. The 1612 MHz masers surround but are offset from the 1720 and 6035 MHz masers which in turn lie close to a compact 22 GHz continuum source embedded in the optical nebula. © 2010 ESO.


Doressoundiram A.,LESIA | Roques F.,LESIA | Boisse Y.,GEPI | Arenou F.,GEPI | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

Serendipitous stellar occultation technique provides a powerful and unique tool to probe the outer Solar system matter, e.g. Kuiper disc and Oort cloud. We present the results of a serendipitous occultation observation campaign carried out with ULTRACAM, mounted on the ESO-VLT telescope, during 2005 May 17-20. The data are processed using the variability index (VI) method modified. The two-colour data set and the VI method allow searching for occulting objects in term of their distance (50, 200 and 5000 au). The analysis of ~34 star-hours provide a working data set for assessing an instrumental approach to search for occultation events by trans-Neptunian objects. We performed recovery tests by implanting synthetic profiles in the data and defining the size of detectable objects to achieve a detection rate of 100 per cent. We propose a Fast Multi-Object Photometer (F-MOP) mounted on a 8-m class telescope and examine its performances. Such instrumental approach from the ground is able to exploit the occultation method for the exploration of the trans-Neptunian region, with a high efficiency. © 2012 The Authors.


Monier R.,CNRS Laboratory for Space Studies and Astrophysical Instrumentation | Monier R.,Sophia University | Gebran M.,Notre Dame University - Louaize | Royer F.,GEPI
Astronomy and Astrophysics | Year: 2015

Context. We have discovered four new HgMn stars while monitoring a sample of apparently slowly rotating superficially normal bright late-B and early-A stars in the northern hemisphere. Aims. Important classification lines of Hg ii and Mn ii are found as conspicuous features in the high resolution SOPHIE spectra of these stars (R = 75 000). Methods. Several lines of Hg ii, Mn ii and Fe ii were synthesized using model atmospheres and the spectrum synthesis code SYNSPEC48, including hyperfine structure of various isotopes when relevant. These synthetic spectra were compared to high-resolution observations of these stars that have a high signal-to-noise ratio to derive abundances of these key elements. Results. The four stars are found to have distinct enhancements of Hg and Mn, which shows that they are not superficially normal B and A stars, but are new HgMn stars and need to be reclassified as such. © 2015 ESO.


Hill V.,University of Nice Sophia Antipolis | Lecureur A.,GEPI | Gomez A.,GEPI | Zoccali M.,University of Santiago de Chile | And 7 more authors.
Astronomy and Astrophysics | Year: 2011

Aims. We seek to constrain the formation of the Galactic bulge by analysing the detailed chemical composition of a large sample of red clump stars in Baade's window. These stars were selected to minimise the contamination by other Galactic components, so they are good tracers of the bulge metallicity distribution in Baade's window, at least for stars more metal-rich than ∼-1.5. Methods. We used an automatic procedure to measure [Fe/H] differentially with respect to the metal-rich star μLeo in a sample of 219 bulge red clump stars from R = 20 000 resolution spectra obtained with FLAMES/GIRAFFE at the VLT. For a subsample of 162 stars, we also derived [Mg/H] from spectral synthesis xaround the Mg  i triplet at λ 6319 Å. Results. The Fe and Mg metallicity distributions are both asymmetric with median values of +0.16 and +0.21, respectively. They show only a small proportion of stars at low metallicities, extending down to [Fe/H] =-1.1 or [Mg/H] =-0.7. The iron distribution is clearly bimodal, as revealed both by a deconvolution (from observational errors) and a Gaussian decomposition. The decomposition of the observed Fe and Mg metallicity distributions into Gaussian components yields two populations of equal sizes (50% each): a metal-poor component centred on [Fe/H] =-0.30 and [Mg/H] =-0.06 with a large dispersion and a narrow metal-rich component centred on [Fe/H] = +0.32 and [Mg/H] = +0.35. The metal-poor component shows high [Mg/Fe] ratios (around 0.3), while stars in the metal-rich component are found to have nearly solar ratios. Kinematical differences between the two components have also been found: the metal-poor component shows kinematics compatible with an old spheroid, while the metal-rich component is consistent with a population supporting a bar. In view of their chemical and kinematical properties, we suggest different formation scenarii for the two populations: a rapid formation time scale as an old spheroid for the metal-poor component (old bulge) and for the metal-rich component, a formation on a longer time scale driven by the evolution of the bar (pseudo-bulge). The observations are described well by a simple model consisting of two components: a simple closed box model to predict the metal-poor population contribution and a local thin disc metallicity distribution, shifted in metallicity, to represent the metal-rich population. The pseudo-bulge is compatible with its being formed from the inner thin disc, assuming high (but plausible) values of the gradients in the early Galactic disc. © 2011 ESO.


Sayede F.,GEPI | Mein P.,LESIA | Amans J.-P.,GEPI | Moity J.,LESIA
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Any future solar telescope project should incorporate an imaging spectrometer. For the future EST (European Solar Telescope) the Observatoire de Paris offers an imaging spectro-porarimetry instrument: a new generation of MSDP. To validate this new generation, we develop a beam slicer prototype that will be tested and validated on optical bench and on existing telescopes. The study assesses the performance gain of such an instrument on a solar 4m class telescope. We present opto-mechanical solutions of a new beam splitter and its implementation in EST. © 2010 Copyright SPIE - The International Society for Optical Engineering.


Rettura A.,Johns Hopkins University | Rosati P.,European Southern Observatory | Nonino M.,National institute for astrophysics | Fosbury R.A.E.,ST ECF | And 6 more authors.
Astrophysical Journal | Year: 2010

We derive stellar masses, ages, and star formation histories (SFHs) of massive early-type galaxies in the z = 1.237 RDCS1252.9-2927 cluster and compare them with those measured in a similarly mass-selected sample of field contemporaries drawn from the Great Observatories Origin Deep Survey South Field. Robust estimates of these parameters are obtained by comparing a large grid of composite stellar population models with 8-9 band photometry in the rest-frame near-ultraviolet, optical, and IR, thus sampling the entire relevant domain of emission of the different stellar populations. Additionally, we present new, deep U-band photometry of both fields, giving access to the critical far-ultraviolet rest frame, in order to empirically constrain the dependence of the most recent star formation processes on the environment. We also analyze the morphological properties of both samples to examine the dependence of their scaling relations on their mass and environment. We find that early-type galaxies, both in the cluster and in the field, show analogous optical morphologies, follow comparable mass versus size relation, have congruent average surface stellar mass densities, and lie on the same Kormendy relation. We also show that a fraction of early-type galaxies in the field employ longer timescales, τ, to assemble their mass than their cluster contemporaries. Hence, we conclude that while the formation epoch of early-type galaxies only depends on their mass, the environment does regulate the timescales of their SFHs. Our deep U-band imaging strongly supports this conclusion. We show that cluster galaxies are at least 0.5mag fainter than their field contemporaries of similar mass and optical-to-infrared colors, implying that the last episode of star formation must have happened more recently in the field than in the cluster. © 2010. The American Astronomical Society. All rights reserved.


Sayede F.,GEPI | Mein P.,LESIA | Amans J.-P.,GEPI | Moity J.,LESIA
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

For the future European Solar Telescope (EST) the Observatoire de Paris proposes a new generation of MSDP: an imaging spectro-polarimetry instrument. To validate this new generation, we develop a beam slicer prototype that will be tested and validated on an optical bench and on existing telescopes. The prototype called S4I (Spectral Sampling with Slicer for Solar Instrumentation) is under construction and tested at the Observatoire de Paris. It validates the opto-mechanical feasibility of the new beam slicer. The manufacture is now complete: we give a description of the whole system. We give also some results of the first tests. © 2012 SPIE.


Zhong G.H.,CAS National Astronomical Observatories | Zhong G.H.,University of Chinese Academy of Sciences | Liang Y.C.,CAS National Astronomical Observatories | Hammer F.,GEPI | And 4 more authors.
Astronomy and Astrophysics | Year: 2010

Aims.We study the star formation histories (SFH) and stellar populations of 213 red and 226 blue nearly face-on low surface brightness disk galaxies (LSBGs), which are selected from the main galaxy sample of Sloan Digital Sky Survey (SDSS) Data Release Seven (DR7). We also compare the stellar populations and SFH between the two groups. Methods. The sample of both red and blue LSBGs have sufficient signal-to-noise ratio in the spectral continua. We obtain their absorption-line indices (e.g. Mg2, HδA), Dn(4000) and stellar masses from the MPA/JHU catalogs to study their stellar populations and SFH.Moreover we fit their optical spectra (stellar absorption lines and continua) by using the spectral synthesis code STARLIGHT on the basis of the templates of simple stellar populations (SSPs). Results.We find that red LSBGs tend to be relatively older, of higher metallicity, are more massive and have a higher surface mass density than blue LSBGs. The Dn(4000)-HδA plane shows that perhaps red and blue LSBGs have different SFH: blue LSBGs are more likely to experience a sporadic star formation event now, whereas red LSBGs are more likely to have formed stars continuously over the past 1.2 Gyr. Moreover, the fraction of galaxies that experienced recent sporadic formation events decreases with increasing stellar mass. Furthermore, two sub-samples are defined for both red and blue LSBGs: the sub-sample within the same stellar mass range of 9.5 ≤ log(M*/M⊙) ≤ 10.3, and the surface brightness limiting sub-sample with μ0(R) ≤ 20.7 mag arcsec-2. They show consistent results with the total sample in the corresponding relationships, which confirm that our results of the comparasion of the blue and red LSBGs are robust. © 2010 ESO.


Schnetler H.,United Kingdom Astronomy Center | Laporte P.,GEPI
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

This paper illustrates how the design of an instrument such as the Extremely Large Adaptive Telescope for GaLaxy Evolution (EAGLE) instrument can be simplified. EAGLE is a Wide Field Multi Object Integral Field Unit Spectrometer aimed as a cornerstone instrument for the European Extremely Large Telescope (E-ELT). The instrument is rich in capabilities and will require Adaptive Optics to ensure that the expected spatial resolution (typically 15 times finer than that of a seeing limited instrument) can be met. The complexities introduced by the need to include a Multi- Object Adaptive Optics system (MOAO) can be simplified by using well defined systems engineering processes. These processes include the capturing, analysis and flow down of requirements, functional and performance analysis and an integrated system design approach. In this paper we will also show by example why the discipline imposed by the UK ATC formal systems engineering process is necessary, especially given that projects such as EAGLE also have to deal with the complexities of international collaborations. It also illustrates how the process promotes innovation and creativity. © 2010 Copyright SPIE - The International Society for Optical Engineering.


Welsh B.Y.,University of California at Berkeley | Wheatley J.,University of California at Berkeley | Lallement R.,GEPI
Publications of the Astronomical Society of the Pacific | Year: 2011

We present medium-resolution ultraviolet interstellar absorption measurements recorded with the HST-COS and FUSE spectrographs toward the post-AGB star Barnard 29 in the M13 globular cluster. Inspection of the UV spectra has revealed absorption at V LSR ∼ -60 km s -1 in the absorption profiles of the C I, C II, C II *, C IV, N I, N II, N V, O I, ALII, Si II, Si IV, S II and Fe II ions. This component can be associated with an intermediatevelocity cloud (IVC), previously identified by both radio and visible observations. More importantly, these data have newly revealed high-velocity absorption at V LSR = -121 ± 3 km s -1 in the UVions of C II, C III, C IV, N II, Si II, and Si IV. This absorption is thought to arise in a highly ionized, multiphase high-velocity cloud (HVC) located a distance of 0.46 < z < 4.7 kpc and has no measurable counterpart in the 21 cm neutral H I emission profile or the normal tracers of neutral gas in the ISM such as Na I, N I or O I. This makes it one of the four nearest highly ionized HVCs yet discovered. The observed column density ratios of the H V components to the C IV and Si IV lines are consistent with values predicted for a turbulent mixing layer or shock ionization of a gas cloud. We have derived estimates of the abundance ratios of C and Si with respect to N relative to their corresponding solar values. Our results indicate values of [Si/N] > +0.40 ± 0.21 and [C/N] = +0.10 ± 0.25 for the HVC gas component. These values indicate that the H V gas has higher than solar relative abundances, consistent with gas of a supersolar metallicity. Several other highly ionized HVCs with distances of less than 7.5 kpc have recently been shown to possess similarly high-metallicity values that are consistent with an origin in condensing returning gas from a galactic fountain. © 2011. The Astronomical Society of the Pacific.

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