Lam Laboratoire Dastrophysique Of Marseille

Marseille, France

Lam Laboratoire Dastrophysique Of Marseille

Marseille, France
SEARCH FILTERS
Time filter
Source Type

Mobasher B.,University of California at Riverside | Dahlen T.,US Space Telescope Science Institute | Ferguson H.C.,US Space Telescope Science Institute | Acquaviva V.,Brooklyn College | And 33 more authors.
Astrophysical Journal | Year: 2015

This is the second paper in a series aimed at investigating the main sources of uncertainty in measuring the observable parameters in galaxies from their spectral energy distributions (SEDs). In the first paper we presented a detailed account of the photometric redshift measurements and an error analysis of this process. In this paper we perform a comprehensive study of the main sources of random and systematic error in stellar mass estimates for galaxies, and their relative contributions to the associated error budget. Since there is no prior knowledge of the stellar mass of galaxies (unlike their photometric redshifts), we use mock galaxy catalogs with simulated multi-waveband photometry and known redshift, stellar mass, age and extinction for individual galaxies. The multi-waveband photometry for the simulated galaxies were generated in 13 filters spanning from U-band to mid-infrared wavelengths. Given different parameters affecting stellar mass measurement (photometric signal-to-noise ratios (S/N), SED fitting errors and systematic effects), the inherent degeneracies and correlated errors, we formulated different simulated galaxy catalogs to quantify these effects individually. For comparison, we also generated catalogs based on observed photometric data of real galaxies in the Great Observatories Origins Deep Survey-South field, spanning the same passbands. The simulated and observed catalogs were provided to a number of teams within the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey collaboration to estimate the stellar masses for individual galaxies. A total of 11 teams participated, with different combinations of stellar mass measurement codes/methods, population synthesis models, star formation histories, extinction and age. For each simulated galaxy, the differences between the input stellar masses, Minput, and those estimated by each team, Mest, is defined as Δ log (M) ≡ log (Mestimated) - log(Minput) and used to identify the most fundamental parameters affecting stellar mass estimate in galaxies, with the following results. (1) No significant bias in Δ log(M) was found among different codes, with all having comparable scatter (σ (Δ log(M)) = 0.136 dex). The estimated stellar mass values are seriously affected by low photometric S/N, with the rms scatter increasing for galaxies with HAB > 26 mag; (2) A source of error contributing to the scatter in Δ log(M) is found to be due to photometric uncertainties (0.136 dex) and low resolution in age and extinction grids when generating the SED templates; (3) The median of stellar masses among different methods provides a stable measure of the mass associated with any given galaxy (σ (Δ log(M)) = 0.142 dex); (4) The Δ log(M) values are strongly correlated with deviations in age (defined as the difference between the estimated and expected values), with a weaker correlation with extinction; (5) The rms scatter in the estimated stellar masses due to free parameters (after fixing redshifts and initial mass function) are quantified and found to be σ (Δ log(M)) = 0.110 dex; (6) Using the observed data, we studied the sensitivity of stellar masses to both the population synthesis codes and inclusion of nebular emission lines and found them to affect the stellar mass by 0.2 and 0.3 dex respectively. © 2015. The American Astronomical Society. All rights reserved.


Maquet L.,Lille University of Science and Technology | Colas F.,Lille University of Science and Technology | Jorda L.,Lam Laboratoire Dastrophysique Of Marseille | Crovisier J.,University Paris Diderot
Astronomy and Astrophysics | Year: 2012

The gravitational orbit of a comet is affected by the sublimation of water molecules by the nucleus when the comet approaches perihelion. This outgassing triggers a non-gravitational force (NGF) that significantly modifies the orbit of the comet. Up to now, modelling of this effect is mostly based on an empirical model defined in the early 70s that uses a simplified outgassing model. Attempts have been made to use advanced anisotropic thermal models both to calculate the NGF taking several observational constraints into account and to retrieve the nucleus's mass and density, but (i) this approach is restricted to a handful of cometary nuclei that are sufficiently well known to allow this type of modelling, and (ii) the authors usually do not fit the astrometric measurements directly but rather non-gravitational parameters calculated with the above-mentioned empirical model. We present a new model for non-gravitational forces with the aim of revisiting the problem of NGF calculation and nucleus density determination. Our model is closer to the nucleus outgassing physics with only a few free parameters. The amplitude of the perturbation depends on several parameters describing the comet activity that can be constrained by visible, infrared, and radio observations of the coma and the nucleus of the comet. It also depends on the nucleus mass, which can in turn be determined by modelling the effect of the NGF on the orbit of a comet. The method is based on the decomposition of the surface of the nucleus in several elements located at different latitudes. The contribution of each surface element to the overall NGF is fitted from the astrometric measurements, together with the density of the nucleus. This method is the only one available so far to estimate the density of cometary nuclei from ground-based observations. This method is tested on the well-known comet 19P/Borrelly. The density found for these comet is between 150 and 600 kg m-3. © ESO, 2012.


Adrian-Martinez S.,Polytechnic University of Valencia | Albert A.,Institut Universitaire de France | Andre M.,University of Barcelona | Anghinolfi M.,National Institute of Nuclear Physics, Italy | And 151 more authors.
Astrophysical Journal Letters | Year: 2014

A search for cosmic neutrino sources using six years of data collected by the ANTARES neutrino telescope has been performed. Clusters of muon neutrinos over the expected atmospheric background have been looked for. No clear signal has been found. The most signal-like accumulation of events is located at equatorial coordinates R.A. =-46.°8 and decl. =-64.°9 and corresponds to a 2.2σ background fluctuation. In addition, upper limits on the flux normalization of an E -2 muon neutrino energy spectrum have been set for 50 pre-selected astrophysical objects. Finally, motivated by an accumulation of seven events relatively close to the Galactic Center in the recently reported neutrino sample of the IceCube telescope, a search for point sources in a broad region around this accumulation has been carried out. No indication of a neutrino signal has been found in the ANTARES data and upper limits on the flux normalization of an E -2 energy spectrum of neutrinos from point sources in that region have been set. The 90% confidence level upper limits on the muon neutrino flux normalization vary between 3.5 and 5.1 × 10 -8 GeV cm-2 s-1, depending on the exact location of the source. © 2014. The American Astronomical Society. All rights reserved.


Gotz D.,CEA Saclay Nuclear Research Center | Osborne J.,University of Leicester | Cordier B.,CEA Saclay Nuclear Research Center | Paul J.,CEA Saclay Nuclear Research Center | And 16 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

We present the Microchannel X-ray Telescope, a new light and compact focussing telescope that will be ying on the Sino-French SVOM mission dedicated to Gamma-Ray Burst science. The MXT design is based on the coupling of square pore micro-channel plates with a low noise pnCCD. MXT will provide an effective area of about 50 cm2, and its point spread function is expected to be better than 3.7 arc min (FWHM) on axis. The estimated sensitivity is adequate to detect all the afterglows of the SVOM GRBs, and to localize them to better then 60 arc sec after five minutes of observation. © 2014 SPIE.


Zakamska N.L.,Johns Hopkins University | Zakamska N.L.,Institute for Advanced Study | Hamann F.,University of California | Paris I.,Lam Laboratoire Dastrophysique Of Marseille | And 8 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

Black hole feedback is now a standard component of galaxy formation models. These models predict that the impact of black hole activity on its host galaxy likely peaked at z = 2-3, the epoch of strongest star formation activity and black hole accretion activity in the Universe. We used XSHOOTER on the Very Large Telescope to measure rest-frame optical spectra of four z ~ 2.5 extremely red quasars with infrared luminosities ~1047 erg s-1. We present the discovery of very broad (full width at half max = 2600-5000 km s-1), strongly blueshifted (by up to 1500 km s-1) [OIII] λ5007Å emission lines in these objects. In a large sample of type 2 and red quasars, [O III] kinematics are positively correlated with infrared luminosity, and the four objects in our sample are on the extreme end in both [OIII] kinematics and infrared luminosity. We estimate that at least 3 per cent of the bolometric luminosity in these objects is being converted into the kinetic power of the observed wind. Photo-ionization estimates suggest that the [OIII] emission might be extended on a few kpc scales, which would suggest that the extreme outflow is affecting the entire host galaxy of the quasar. These sources may be the signposts of the most extreme form of quasar feedback at the peak epoch of galaxy formation, and may represent an active 'blow-out' phase of quasar evolution. © 2016 The Authors.


Zakamska N.L.,Johns Hopkins University | Zakamska N.L.,Institute for Advanced Study | Hamann F.,University of California at Riverside | Paris I.,Lam Laboratoire Dastrophysique Of Marseille | And 8 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2016

Black hole feedback is now a standard component of galaxy formation models. These models predict that the impact of black hole activity on its host galaxy likely peaked at z = 2-3, the epoch of strongest star formation activity and black hole accretion activity in the Universe. We used XShooter on the Very Large Telescope to measure rest-frame optical spectra of four z ~ 2.5 extremely red quasars with infrared luminosities ~1047 erg s-1. We present the discovery of very broad (full width at half max = 2600-5000 km s-1), strongly blueshifted (by up to 1500 km s-1) [O III] λ5007 Å emission lines in these objects. In a large sample of type 2 and red quasars, [O III] kinematics are positively correlated with infrared luminosity, and the four objects in our sample are on the extreme end in both [O III] kinematics and infrared luminosity. We estimate that at least 3 per cent of the bolometric luminosity in these objects is being converted into the kinetic power of the observed wind. Photo-ionization estimates suggest that the [O III] emission might be extended on a few kpc scales, which would suggest that the extreme outflow is affecting the entire host galaxy of the quasar. These sources may be the signposts of the most extreme form of quasar feedback at the peak epoch of galaxy formation, and may represent an active 'blow-out' phase of quasar evolution. © 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


Aguilar J.A.,University of Valencia | Al Samarai I.,Aix - Marseille University | Albert A.,Institut Universitaire de France | Andre M.,University of Barcelona | And 107 more authors.
Astroparticle Physics | Year: 2011

An algorithm is presented, that provides a fast and robust reconstruction of neutrino induced upward-going muons and a discrimination of these events from downward-going atmospheric muon background in data collected by the ANTARES neutrino telescope. The algorithm consists of a hit merging and hit selection procedure followed by fitting steps for a track hypothesis and a point-like light source. It is particularly well-suited for real time applications such as online monitoring and fast triggering of optical follow-up observations for multi-messenger studies. The performance of the algorithm is evaluated with Monte Carlo simulations and various distributions are compared with that obtained in ANTARES data. © 2011 Elsevier B.V. All rights reserved.


Leyrat C.,University of Paris Descartes | Fornasier S.,University of Paris Descartes | Barucci A.,University of Paris Descartes | Magrin S.,University of Padua | And 10 more authors.
Planetary and Space Science | Year: 2010

We investigate the possible presence of heterogeneous surface features on asteroid (2867) Steins, using the G-mode multivariate statistical method (Coradini et al., 1977) applied to Rosetta/OSIRIS images. We analyze both NAC and WAC images obtained near around the closest approach that occurred on September 5th, 2008, through different filters centered on wavelengths ranging from 295 to 986 nm. The shape of Steins is modeled as a polyhedron of almost 58 000 facets. Photometric corrections were performed using Hapke's (2002) model to compensate for the variable illuminations conditions at the surface. The G-mode classification method was performed on all visible and illuminated facets, i.e. in a region limited to [-50°,60°] in latitude and [-40°,90°] in longitude, that represents almost 30% of the total surface. The analyzed set of facets does not show any significant difference in the reflected light content, suggesting no surface inhomogeneities larger than 4% at the 95% confidence level. © 2010 Elsevier Ltd. All rights reserved.


Gunn J.E.,Princeton University | Carr M.,Princeton University | Smee S.A.,Johns Hopkins University | Orndorff J.D.,Johns Hopkins University | And 19 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

We describe the conceptual design of the camera cryostats, detectors, and detector readout electronics for the SuMIRe Prime Focus Spectrograph (PFS) being developed for the Subaru telescope. The SuMIRe PFS will consist of four identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each spectrograph will have three channels covering wavelength ranges 3800 Å - 6700 Å, 6500 Å - 10000 Å, and 9700 Å - 13000 Å, with the dispersed light being imaged in each channel by a f/1.10 vacuum Schmidt camera. In the blue and red channels a pair of Hamamatsu 2K x 4K edge-buttable CCDs with 15 um pixels are used to form a 4K x 4K array. For the IR channel, the new Teledyne 4K x 4K, 15 um pixel, mercury-cadmium-telluride sensor with substrate removed for short-wavelength response and a 1.7 um cutoff will be used. Identical detector geometry and a nearly identical optical design allow for a common cryostat design with the only notable difference being the need for a cold radiation shield in the IR camera to mitigate thermal background. This paper describes the details of the cryostat design and cooling scheme, relevant thermal considerations and analysis, and discusses the detectors and detector readout electronics. © 2012 SPIE.


Dupouy C.,CNRS Physics Laboratory | Benielli-Gary D.,Lam Laboratoire Dastrophysique Of Marseille | Neveux J.,French National Center for Scientific Research | Dandonneau Y.,University Pierre and Marie Curie | Westberry T.K.,Oregon State University
Biogeosciences | Year: 2011

Trichodesmium, a major colonial cyanobacterial nitrogen fixer, forms large blooms in NO 3-depleted tropical oceans and enhances CO 2 sequestration by the ocean due to its ability to fix dissolved dinitrogen. Thus, its importance in C and N cycles requires better estimates of its distribution at basin to global scales. However, existing algorithms to detect them from satellite have not yet been successful in the South Western Tropical Pacific (SP). Here, a novel algorithm (TRICHOdesmium SATellite) based on radiance anomaly spectra (RAS) observed in SeaWiFS imagery, is used to detect Trichodesmium during the austral summertime in the SP (5° S-25° S 160° E-170° W). Selected pixels are characterized by a restricted range of parameters quantifying RAS spectra (e.g. slope, intercept, curvature). The fraction of valid (non-cloudy) pixels identified as Trichodesmium surface blooms in the region is low (between 0.01 and 0.2 %), but is about 100 times higher than deduced from previous algorithms. At daily scales in the SP, this fraction represents a total ocean surface area varying from 16 to 48 km 2 in Winter and from 200 to 1000 km 2 in Summer (and at monthly scale, from 500 to 1000 km 2 in Winter and from 3100 to 10 890 km 2 in Summer with a maximum of 26 432 km 2 in January 1999). The daily distribution of Trichodesmium surface accumulations in the SP detected by TRICHOSAT is presented for the period 1998-2010 which demonstrates that the number of selected pixels peaks in November-February each year, consistent with field observations. This approach was validated with in situ observations of Trichodesmium surface accumulations in the Melanesian archipelago around New Caledonia, Vanuatu and Fiji Islands for the same period. © 2011 Author(s).

Loading Lam Laboratoire Dastrophysique Of Marseille collaborators
Loading Lam Laboratoire Dastrophysique Of Marseille collaborators